April 23 - 29, 2016 New Scientist

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LIVING FOSSILS

What Neanderthal DNA does for us

PYONG BANG

Worrying rumbles from North Korea’s supervolcano

LIGO LEVELS UP

Most sensitive instrument ever gets an upgrade WEEKLY April 23 - 29, 2016

CAN’T PICTURE IT The people who don’t have a mind’s eye

LIFE,THESOLARSYSTEMANDEVERYTHING T HE STORY OF OU R COSM IC OR IGI N IS A LL W RONG

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ATOMIC LIBRARY All of human knowledge on a pinhead

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Professor Dame Carol Robinson 2015 Laureate for United Kingdom

By Brigitte Lacombe

Science needs women

L’ORÉAL UNESCO AWARDS

Dame Carol Robinson, Professor of Chemistry at Oxford University, invented a ground-breaking method for studying how membrane proteins function, which play a critical role in the human body. Throughout the world, exceptional women are at the heart of major scientific advances. For 17 years, L’Oréal has been running the L’Oréal-UNESCO For Women In Science programme, honouring exceptional women from around the world. Over 2000 women from over 100 countries have received our support to continue to move science forward and inspire future generations. JOIN US ON FACEBOOK.COM/FORWOMENINSCIENCE

CONTENTS

Volume 230 No 3070

This issue online newscientist.com/issue/3070

Leaders

News

5

8

News

Wave hunter gets a reboot

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UPFRONT New heat record. Ecuador and Japan’s deadly quakes. Dementia falling in men. Brexit’s effect on environment and science 8 THIS WEEK Dolphins “talk” to solve problems. Cow’s milk boosts babies’ good bacteria. Atoms as tiny hard drives. North Korea’s supervolcano fears. Face-to-face with coral bleaching 15 IN BRIEF Snakes plan attack. Muddled history makes us “psychic”. Doughnut circling a black hole

CALTECH/MIT/LIGO LAB

Seeker of gravitational waves is now even more sensitive

UK government-funded scientists mustn’t be gagged. We’re heading for a water crisis

On the cover

30

38 Living fossils Neanderthal DNA legacy 10 Pyong bang Supervolcano could blow 8 LIGO powers up Instrument gets upgrade 34 Can’t picture it The people who don’t have a mind’s eye 10 Atomic library All human knowledge on a pinhead

Life, the solar system and everything The story of our cosmic origin is all wrong

Cover image Simon Danaher

Analysis 18 Climate agreement Are countries signing up to a doomed deal? 20 COMMENT Anti-vaccination film should come with health warning. Why we are monogamous 21 BRIEFING Is there a gene for losing your virginity?

Technology 22 Matchmaking by looking at data. Beefing up wireless signals in the body. Ultra-thin electronic skin. Virtual reality tourism

Aperture 26 Insects as you’ve never seen them before

Features

34

Opinion 42 Sucked dry Time to face up to the limits of our freshwater supplies, says Arjen Hoekstra

Can’t picture it

Features 30 Life, the solar system and everything (see above left) 34 Can’t picture it (see left) 38 Living fossils What Neanderthal DNA does for us

DAVID REHOR/MILLENNIUM IMAGES

The people who don’t have a mind’s eye

CultureLab

Coming next week… Unexplained oddities

Why our understanding of reality doesn’t add up

The upside of nightmares

Bad dreams have some surprising benefits

44 The ultimate club Who or what should be admitted to the group of things with a mind? 46 Easy formula Biopic of mathematician Srinivasa Ramanujan plays it a bit too safe

Regulars 52 LETTERS Now find neutrino background 56 FEEDBACK Hot diet trend 57 THE LAST WORD Pieces of eight

23 April 2016 | NewScientist | 3

Entries for $250,000 Ryman Prize now open The Ryman Prize is a unique international award aimed at encouraging the best and the brightest thinkers in the world to focus on ways to improve the health of older people. The world’s ageing population means that in some parts of the globe – including most of the Western world – the population aged 75+ is set to triple in the next 30 years. In order to stimulate fresh efforts in the field, the Ryman Foundation is offering a NZ$250,000 (US$165,000) annual prize for the world’s best

discovery, development, advance or achievement that enhances quality of life for older people. The inaugural Ryman Prize was won by Gabi Hollows for her pioneering work to provide affordable eye surgery for people in developing countries. The Hollows Foundation has restored sight to more than 1 million people – an amazing achievement that has transformed lives. If you have a great idea, or have achieved something remarkable like Gabi, we’d love to hear from you!

Go to www.rymanprize.com for more information

Gabi Hollows and Nobel Laureate Dr Erwin Neher at the presentation of the inaugural Ryman Prize

www.rymanprize.com

REUTERS/CHRIS WATTIE

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Too close to the bone The threat to gag scientists was unnecessary and damaging

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IMAGINE you are a scientist researching a question with implications for public policy: pollution, say, or drug addiction, or vaccines, or fracking, or the rehabilitation of offenders. Should you be allowed to speak out about what your discoveries mean for wider society? In an open and enlightened society, this should not even be a question. But in the UK, the answer almost became no, until a skin-of-the-teeth U-turn from the government. As of next month, a new piece of legislation will prevent anyone who receives UK government funding from using that money to “support activity intended to influence or attempt to influence

Parliament, Government or political parties… or attempting to influence legislative or regulatory action”. The anti-lobbying clause, as it is known, is mainly intended to stop pressure groups from using taxpayers’ money for lobbying. But one of its consequences would have been to gag scientists who receive public money, effectively excluding them from the policymaking process. Earlier this week, with just a few days to go before it became law, the government bowed to pressure and granted scientists an exemption. But the fact that it took so long and went so close to the wire was not an edifying spectacle. Nor did it do much to dispel the

A thirst we must quench IT MAY have taken decades to develop the international will to tackle climate change, but at least everyone agreed on one thing from the outset: we all share the same atmosphere. When a global crisis in the making is masked by seemingly unconnected local problems, it’s even harder to muster a coordinated global response. Stand next to a river and it seems very much like a

local resource. But transnational rivers blur the boundaries and global supply chains complicate them even further. Three-quarters of the UK’s water use, for example, is located outside its borders because of the goods it imports. Half of this externalised water footprint is in countries where water is already scarce (see page 42). While northern Europeans enjoy

idea that this government is not interested in evidence-based policymaking, as suggested by the Psychoactive Substances Act and the snooper’s charter. For now we can give credit where it is due, and breathe a sigh of relief. But the episode has unnecessarily worsened already strained relationships. The fear remains that the UK is going down the same road as Canada, which a few years ago cut science to the bone and muzzled federally funded scientists. That assault on free speech was later reversed, but it did enormous damage to Canada’s reputation as a progressive, pro-science country. The UK must not make the same mistake. ■

Spanish olives and Italian wine, rivers in southern Europe are slowly drying. There are many similar examples. Global manufacturing and trade are ravenous drinking straws, sucking at reservoirs, rivers and aquifers wherever they may be. But at what cost? Only so much rain falls out of the sky in a year, and we need to start thinking more carefully about how we share it. It’s something to consider as we raise a glass for Earth Day this Friday. ■ 23 April 2016 | NewScientist | 5

JOSEP VECINO/ANADOLU AGENCY/GETTY

UPFRONT

No link between quakes JAPAN and Ecuador were both hit by powerful earthquakes in the last week. But despite them both sitting on the seismically active “Ring of Fire” around the Pacific Ocean, there is no evidence of a link between the quakes. At least 42 people were killed in south-west Japan, after the area was rocked by a magnitude 6.2 quake on 14 April and a magnitude 7.0 quake in the early hours of the following Saturday morning. A magnitude 7.8 earthquake also hit the north-west coast of Ecuador at 7 pm local time on the Saturday (pictured), killing at least 272 people and injuring another 2500. Although it is tempting to draw a connection, the timing of quakes is coincidental, says Phil Cummins of the Australian National University

in Canberra. “It’s difficult to see any relation because Japan and Ecuador are very distant from each other,” he says. “Things happen at random – you can get clusters of earthquakes that might appear connected but actually they aren’t.” Nevertheless, both regions may now be at risk of additional quakes and landslides. Indeed, Ecuador and Japan have reported tremors in the days following the big quakes. About 90 per cent of earthquakes occur along the Ring of Fire, where major tectonic plates clash. But while the Ecuador quake resulted from a slip between the South American and Nazca plates, the two Japan quakes were triggered by a fault within a single plate, according to the US Geological Survey.

Dementia drop

Understanding what’s behind this drop could help lower dementia rates further. Lifestyle factors like better diets, improved blood pressure control and more education may all be involved. The much steeper decline in men could be because older men used to have unhealthier lifestyles than women, so they had more room for improvement, says team member Fiona Matthews of Newcastle University, UK. “We have gone from smoking being something that nearly every man did to how it is considered now,” she says.

–Sitting on the Ring of Fire–

Brexit science

own environmental standards, it would set them at a less stringent level than has been imposed by the EU, many witnesses noted. A separate report by a House of Lords committee has concluded that EU membership has boosted scientific research in the UK, largely thanks to extra funding, ease of movement and common regulations. There have been a few downsides, such as the difficulty in getting approval for genetically modified crops. But with member states now free to approve crops on an individual basis, a Brexit would not help in this regard.

THE UK’s membership of the EU has been overwhelmingly good for the environment. That’s according to a report by a House of Commons committee published this week, which also says that membership

has improved the country’s standards and given it a stronger voice in international negotiations. “We bathe on cleaner beaches, drive more fuel-efficient cars and can hold government to account on air pollution,” said Mary Creagh, chair of the house’s Environmental Audit Committee. “Inside the EU we can influence and improve EU environmental law.” No witness to the committee made an environmental case for leaving, and some said the UK has not gone far enough in implementing EU policies and enforcing its laws. If the UK were free to set its 6 | NewScientist | 23 April 2016

MAURIZIO DE ANGELIS/SPL

“We bathe on cleaner beaches and drive more fuel-efficient cars thanks to our EU membership”

IT’S good news – for men. The incidence of dementia in males in the UK has fallen by 41 per cent, but the improvement has been much smaller among women: only a 2.5 per cent drop. That’s according to an analysis of more than 10,000 over-65s in the UK spanning the past 20 years. The study found that, overall, a person’s risk of getting dementia by any particular age is a fifth lower than it was 20 years ago (Nature Communications, DOI: 10.1038/ncomms11398).

Super-clap rise THE drugs don’t work. England’s public health agency has discovered more cases of gonorrhoea that are resistant to nearly all antibiotics. The bacteria behind gonorrhoea readily acquire genes for resisting drugs and so from 2012, UK patients were given two antibiotics at once – azithromycin pills plus a ceftriaxone injection – so if bacteria acquired resistance –Evolving resistance– to one, they would be killed by the

For new stories every day, visit newscientist.com/news

Drone collision?

other. Gonorrhoea that resists azithromycin was detected in Japan in 2013, and clinics in northern England reported 16 people with similarly resistant infections in 2015. That means the bacteria are only killed by ceftriaxone, and there is no backup antibiotic to kill them off if they develop resistance to it. One option may be to increase doses of the existing drugs, or go back to old drugs that might work against gonorrhoea. Researchers are trying to find out if a vaccine against meningitis B, caused by related bacteria, might cause some cross-immunity to gonorrhoea.

IS IT a bird? Is it a drone? A police investigation has been launched after something hit the front of a plane as it was landing at London’s Heathrow airport on Sunday. The finger is being pointed at a drone, and pilots have long warned of the dangers of flying them near airports. There were 40 near-miss events in the UK in 2015, compared with just nine in 2014, according to the UK Airprox Board, which monitors air safety. Now that a collision seems to have happened, efforts to tighten regulations are likely to accelerate.

HAWC’s eye on sky

60 SECONDS

The UK Department of Transport is to publish a strategy review this year. Mandatory in-built technology that restricts where drones can fly is one possibility. However, some feel that’s going too far. “Do we need new laws or new policies? I think not,” says Eli Dourado at George Mason University in Arlington, Virginia. “This is about getting people to comply with existing laws.” The UK’s Air Navigation Order restricts the flight of drones near airports. But the rules lack detail, says Ben Gardner, a solicitor at law firm Pinsent Masons, which advises on technology issues.

Wildlife loves LA limelight, too

ISTOCK /GETTY

A WATERY telescope has just GIVEN the chance to search for new species to add to the world’s released its debut map of the sky, biodiversity databases, where would measuring for the first time how you go? The Amazon rainforest? often black holes flicker on and off. Antarctica? Try Los Angeles. The High Altitude Water Over the past two years, Cherenkov (HAWC) observatory’s entomologist Emily Hartop at the map has also caught pulsars, city’s Natural History Museum has supernova remnants, and other logged 43 species new to science bizarre cosmic beasts in action. HAWC is not a typical telescope. from this concrete jungle. Hartop’s work forms part of the The detector is made up of 300 museum’s plan, announced last tanks, each filled with 200,000 week, to launch the world’s largest litres of water. When high-energy search for hidden urban biodiversity. particles go through the water, It will be recruiting up to a thousand they emit a blue light called citizen scientists to seek out new Cherenkov radiation. This enables species of spiders, snails, reptiles physicists to reconstruct where and amphibians from sites in LA such the particles came from. as backyards and school yards. In its first year, HAWC picked The museum hopes its Urban up 40 distinct sources of gamma rays. One was associated with leftover material from exploding supernovas, another with a pulsar 26,000 light years away. HAWC can also pick up gamma rays from other galaxies , perhaps caused by black holes at their centres. The detector can also pick up changes in gamma ray brightness better than ever before. Just 10 days ago, it saw a flare in a galaxy called Markarian 501. This kind of flaring seems to happen about 5 to 10 times per year. HAWC will also be able to see such a flare from the black hole at –I’m here if you look for me– the centre of our own galaxy.

Nature Research Center will inform ways in which cities worldwide can support biodiversity. “Every city should be doing this,” says Hartop. City streets, industrial sites, parks and gardens were once seen as biological deserts. But their nooks and crannies are turning out to be rich in species. “Los Angeles is home to one of the most diverse ecosystems in the world,” says Brian Brown, the LA museum’s curator of entomology. The city sits in one of the planet’s top 35 biodiversity hotspots. But LA isn’t alone. Across the world, urban landscapes “are as important for biodiversity as ancient woodlands”, says Matt Shardlow of the UK conservation group Buglife.

Hottest ever March March 2016 has been the warmest on record, continuing monthly records set by January and February this year. The record for the warmest year may also fall in 2016, according to early estimates, beating 2015, which in turn broke 2014’s record.

A new Dawn NASA’s Dawn probe is the first ever spacecraft to visit two asteroids, Vesta and Ceres, and now it may fly to another destination. It’s mission at Ceres is set to end this summer, but the mission team has sent a proposal to NASA for an extension to explore a third asteroid, although which one remains a secret.

Coal goes bankrupt The decline of the global coal industry claimed its biggest victim last week when US giant Peabody Energy, the world’s largest privatesector coal company, filed for bankruptcy. The coal boom of the early century is turning to bust as China burns less and renewables slowly take over new investment.

Greenland melts early Spring has begun with an unprecedented early melt of land ice on Greenland. Temperatures soaring above 10°C caused more than a tenth of the island’s vast ice sheet to start melting last week — a month before significant melt usually begins.

Social trips Psilocybin – a key hallucinogen in magic mushrooms – helps people cope with being socially excluded. When playing a game that led to the volunteer being left out, those given psilocybin said they felt less excluded – and showed less activity in brain regions associated with social cognition – than those given a placebo (PNAS, doi.org/bfdq). Similar compounds could be developed for people with mental health disorders, for whom social ties are vital, says the study’s team.

23 April 2016 | NewScientist | 7

THIS WEEK

Next move for cosmic wave-hunter Having sighted gravitational waves, LIGO has much more up its sleeve LIGO, the limiting properties are the brightness of the light that returns to the detector, and the phase of the light waves, which is what the team measure. Surprisingly, there is a loophole. “We can never get around Heisenberg, but we can trick him,” says team member Nergis

Lisa Grossman in Salt Lake City, Utah

8 | NewScientist | 23 April 2016

“An instrument 10 times the size of LIGO could pick up gravitational waves from the first collapsed stars”

CALTECH/MIT/LIGO LAB

GET ready for gravitational waves: the sequel. In February, the LIGO collaboration announced its groundbreaking detection of gravitational waves – ripples in space-time produced by clashing black holes and predicted by Einstein a century ago. Now the team are preparing for their next feat: spotting ever fainter cosmic sources of these waves. Although recently upgraded to become Advanced LIGO, the Laser Interferometer GravitationalWave Observatory isn’t at full strength yet. When it is, it will be able to measure changes in distance as small as one-tenthousandth the width of a proton. But there are several hurdles to overcome first, not least the laws of physics. At this week’s American Physical Society meeting in Salt Lake City, Utah, researchers planned their attack. LIGO’s twin detectors, one in Washington state and one in Louisiana, are L-shaped tunnels 4 kilometres long. To pick up the stretching and squeezing of space-time caused by a passing gravitational wave, physicists shine a laser down each arm to reflect off a mirror at the end. When the beam returns to the detector’s elbow, they recombine it with the light from the other arm to see if the beams are still in phase, meaning they went the same distance. If not, they have caught a gravitational wave. But to be sure of this, every wobble of the tunnels must be accounted for. That includes tiny movements caused by the ocean, the rumble of passing cars, even the laser itself. One strategy is to keep the mirrors away from the ground. “The noisy ground is producing a

Mavalvala at the Massachusetts Institute of Technology. It turns out you can send the light through a special kind of crystal to “squeeze” it into favouring one property. In this case, they can reduce brightness to boost phase detection. “It’s a little bit magical,” says Jonathan Cripe of Louisiana State University in Baton Rouge, who wants to use specialised micromirrors instead of crystals to do the squeezing. The team plan to –A new mirror to the universe– include this and all the other possible fixes in an upgrade called very steep limit to our sensitivity,” example, leading to mirrors being A+, to happen in a few years’ time. nudged when they shouldn’t be. says Katherine Dooley of the Only a bigger detector can So Dooley and her colleagues University of Mississippi in Lewis. outdo A+. Physicists are already are working on suspending the “You get to a point where you can dreaming of one with arms seismometers from a scaffold as tell from the shape of the signal, 10 times as long as LIGO’s. well. The biggest challenge is oh, that’s a train coming.” Tentatively called the Cosmic finding the right material for the Explorer, it would pick up cord: it must be strong, yet bendy gravitational waves of much lower Wobbly accounting enough not to transmit motion. frequency arriving from much To counter this noise, the They are using steel, and want to greater distances – potentially team suspend the mirrors from upgrade to strands of glass. glimpsing the collapsed remnants an isolated scaffold. They also There’s a more fundamental of the very first stars. measure the ground’s motion limit to LIGO’s sensitivity: In some ways, this is actually a with seismometers and nudge quantum mechanics. At higher modest undertaking, says Sheila the mirrors in real time to cancel gravitational wave frequencies, Dwyer of the California Institute it out. But this can’t distinguish the Heisenberg uncertainty of Technology in Pasadena. With between a quake shaking the principle becomes a factor. It says funding and a suitable site, we mirrors and local effects that that for certain pairs of properties, could build it today. “There’s no affect only the seismometers. the more accurately you can assumption that technology A strong wind can tilt the building measure one, the less accurately would need to advance to make housing the seismometers, for you can measure the other. For this happen,” she says. ■

In this section ■ Using atoms as tiny hard drives, page 10 ■ Climate agreement: are countries signing a doomed deal?, page 18 ■ Matchmaking by looking at data, page 22

Cow’s milk carb boosts a baby’s good bacteria COW’S milk straight up may be longum infantis, or B. infantis for off the menu for young babies, short. “Up to 90 per cent of a but one of its ingredients seems baby’s gut bacteria can be B. to encourage the growth of a infantis,” says David Mills at the healthy set of gut bugs, much as University of California at Davis. breast milk does. Cow’s milk itself “If you don’t have infantlacks essential nutrients but the associated Bifidobacteria, a type compound could be added to called bacteroides can become infant formula. dominant, and encourage the Breast milk is a wonder drink growth of E. coli.” for newborns. It contains a host Now Mills’s team has found of beneficial components, such that oligosaccharides in cow’s as antibodies that protect a baby “A nutrient in cow’s milk from disease, and the proteins, could provide a ready vitamins and fat needed for source of prebiotics for development. It also contains use in infant formula” oligosaccharides – carbohydrates that act as prebiotics and encourage the growth of the milk can encourage B. infantis to right gut bacteria. thrive. They used an enzyme to This is important: a baby’s first separate the oligosaccharides collection of bacteria is thought from the proteins in cow’s milk, to affect which other microbial and tried growing the bacteria species are able to make a home on each of the two nutrients. B. in their gut. Allowing the wrong infantis failed to grow on the ones to dominate can put a person proteins from the milk. But the at risk of developing all sorts of oligosaccharide had striking disorders, including obesity and effects, encouraging the bacteria even Parkinson’s disease. to grow dramatically. A baby’s gut microbiome is far Interestingly, it had no impact simpler than that of a healthy on similar strains of bacteria adult. It is usually dominated by commonly found in adults – it a single species – Bifidobacteria only worked on the infant strain

YOU must be pulling my flipper. Bottlenose dolphins have been seen chattering to each other while solving a tricky puzzle, hinting they have vocalisations dedicated to cooperating on problem-solving. Holli Eskelinen of the Dolphins Plus research institute in Florida and her colleagues presented a group of six captive dolphins with a locked canister filled with food (pictured below). The canister could only be opened by simultaneously pulling a –Soup it up with prebiotics– rope at either end of it. The team conducted 24 trials, during which all six dolphins were present. Only two (Applied and Environmental of the dolphins managed to crack Microbiology, doi.org/bfcz). the puzzle and get to the food. “It’s a bit of a surprise, because In 20 of the trials, the same human milk is so different to two adult males worked together cow’s milk,” says Mills. to open the food canister within just Because of those differences 30 seconds. In the other four trials, cow’s milk isn’t recommended one of the two males opened it for children under 1. But in terms alone, but this was much trickier of the oligosaccharides at least, and took longer. the two types of milk are actually When the dolphins teamed up, similar, says Mills. This means they made more vocalisations than that cow’s milk – and potentially they did while opening the canister the milk of other animals – on their own or when there was either could provide a ready source no canister present or no interaction of these prebiotics for adding with the canister (Animal Cognition, to infant formula. doi.org/bfct). Karen Scott at the University “The results point toward the of Aberdeen, UK, agrees. “It looks possibility of a dolphin language that like if you pre-treat cow’s milk enables team problem-solving,” says with an enzyme, you could have marine ecologist Leigh Torres at a low-cost source of useful Oregon State University. Robin Wylie ■ oligosaccharides, which are

difficult to manufacture,” she says. One source could be whey permeate – a by-product of cheese-making. At the moment, this tends to be thrown away, but it could contain plenty of useful oligosaccharides, says Mills. Mills’s wider goal is to figure out exactly what makes for an ideal microbiome in babies. “The more we know about what B. infantis looks like, the better we can diagnose a healthy gut in a healthy child,” he says. Jessica Hamzelou ■

BRIAN SKERRY/NATIONAL GEOGRAPHIC

THANASIS ZOVOILIS/GETTY

Dolphins chat when teaming up to do tasks

–Come on, butterflippers– 23 April 2016 | NewScientist | 9

THIS WEEK

Smallest storage uses atoms for bits chlorine atoms on a copper surface that is dented with pits, called vacancies. A scanning tunnelling microscope (STM) picks up individual atoms and moves them into or out of the vacancies. The presence or absence of an atom in each pit represents either a 1 or 0. A kilobyte isn’t particularly useful by itself – it’s only enough to store a handful of tweets – but larger versions of the memory could shrink even the biggest

IT’S A memory so small you’ll forget where you left it. A new data storage system uses single atoms as computer bits, and could hold the contents of the US Library of Congress in a cube just 100 micrometres across – little more than a speck of dust. Researchers have been trying for years to develop data storage using single atoms as bits – the 1s and 0s that form the basic units of information in a computer. Eight bits make up one byte, which can represent a single letter or number. Today’s hard disc drives use billions of atoms to represent a few bytes, and the average hard disc holds a trillion bytes. In 2012, a team at IBM developed a 12-atom bit, with 96 atoms representing one byte. But Sander Otte at the Delft University of Technology in the Netherlands and his colleagues, including some who worked with the IBM team, have now built a vast number of one-atom bits. Their memory holds 8128 bits, or a kilobyte, and measures just 96 nanometres by 126 nanometres. The memory is made of

North Korea and West align over supervolcano IF IT blows again, it would make Vesuvius look like a tea party. Mount Paektu, a supervolcano on North Korea’s border with China, is starting to yield its secrets, thanks to a ground-breaking collaboration between the West and North Korea. Paektu’s last eruption, a thousand years ago, is the second largest ever recorded. “If it erupted, it would have 10 | NewScientist | 23 April 2016

CERN/SCIENCE PHOTO LIBRARY

Rebecca Boyle

impacts way beyond Korea and China,” says James Hammond of Birkbeck, University of London, one of the scientists involved. Yet little is known about this enigmatic volcano, which has been closely monitored ever since suspicious bulges were seen between 2002 and 2005. GPS measurements showed ground deformations there, which were accompanied by increased gas emissions and seismic rumbles. Hammond and others were invited to North Korea in 2011 to help study the volcano. Their research has now revealed an extensive magma

datasets. “There is no physical limitation that prevents the fabrication of much larger atomic memories,”the team says (arxiv. org/abs/1604.02265). To test the memory, the team recreated the 8-bit ASCII codes that represent single characters in computer text files. This atomic dictionary implies that the contents of the entire US Library of Congress – 1 million gigabytes – could be condensed into a 100 micrometre cube. Using the ASCII codes, the researchers stored part of the text of a 1959 lecture by the famed physicist Richard Feynman, titled “There’s plenty of room at the bottom”, in which he speculates that one day we will be able to

rearrange atoms. They also demonstrated that the memory could be rewritten, by storing a sample from Charles Darwin’s On the Origin of Species afterwards. Moving the atoms requires a tiny amount of energy, but the whole apparatus requires cooling to -196 °C, since anything warmer makes the atoms clump together. The memory is also slow. Reading a block of 8 bytes takes about a minute, and rewriting it takes 2 minutes. Tiny disturbances can affect the atoms or the delicate STM tip, and as a result, several atomic bits were unreadable, leading to gaps and missing words. Even with these limitations, the work is a major advance, says Franz Himpsel of the University of Wisconsin-Madison. The densest storage available today offers 6 to 12 terabits per square centimetre, compared with more than 3000 terabits per square centimetre for atomic storage. “That is a few hundred times denser than what you can buy from companies like Seagate, and what Google and Amazon have in their disc farms,” he says. Scaling up to gigabyte-sized memory would be no mean feat, but it appears possible, he says. “There is a lot more to do, but just like with silicon technology, once you figure out how to do it, you can scale up, and just repeat, –We’re finding Feynman’s bottom– repeat, repeat.” ■

reservoir beneath the volcano (Science Advances, doi.org/bfcw). “It’s a mushy mixture of molten rock and crystals that goes down right through the crust around 35 kilometres deep,” says Hammond. It’s rare to see a partially melted type of magma with such a large fluid component throughout the whole crust, he says. It is a potential source of material for eruptions, and the

“North Koreans are very open to science cooperation with the West in most research areas”

researchers are working to unravel the level of risk of an eruption any time soon. After years working together, the teams have got to know each other well, and in the evening eat together or even head to a karaoke bar. “With what we’re doing, there’s no political element – we’re involved to understand a huge volcano. The fact we’re having this dialogue is a great example of science transcending political differences,” says Hammond. “The Koreans are very open to science engagement in most areas.” Andy Coghlan ■

THE WONDERS OF SPACE

Take a fantastic journey through the most mind-blowing sights of the cosmos – the sun, the moon, Mars, Pluto, black holes, the Milky Way, comets, Hubble’s best images and much more Buy your copy from all good magazine retailers or digitally. Find out more at newscientist.com/TheCollection

THIS WEEK FIELD NOTES Great Barrier Reef, Australia

Laura Hampton

EVEN to the untrained eye, it’s obvious that the Great Barrier Reef is in more than a little hot water. As I board my charter flight from Cairns, bound for the remote scientific research station on Lizard Island, I prepare myself mentally for devastating scenes. Soon the tropical green of Queensland’s northern coast is replaced by bright turquoise waters, and my fears are realised. The sea is awash with white. Reefs that were once among the world’s most unspoiled now languish under a baking sky, every one seemingly bleached. My pilot turns and gives me a thumbs down, shaking his head sombrely. This is the worst bleaching event ever recorded at the Great Barrier Reef, says Terry Hughes, director at the ARC Centre of Excellence for Coral Reef Studies in Townsville. “It’s already very clear that what we are seeing here is much greater than back in 2002, which in turn was greater than 1998,” says Hughes, referring to the last two major bleachings. Bleaching happens when corals become stressed and expel

Coral in crisis Surveys conducted at the Lizard Island Research Station are revealing the vast extent of bleaching at the Great Barrier Reef Great Barrier Reef Lizard Island Cairns AUSTRALIA A A Brisbane

12 | NewScientist | 23 April 2016

OLIVER LUCANUS/MINDEN/CORBIS

Caught in death’s warm embrace photosynthetic algae called zooxanthellae living inside them, which provide up to 90 per cent of the corals’ energy needs. Corals can survive this, but will die if not swiftly recolonised by the algae.

Record El Niño This year’s bleaching has been linked to the strongest El Niño event on record and to climate change, both of which are heating up the ocean. “The baseline of sea temperature is going up decade by decade due to global warming,” says Hughes. “When an El Niño event comes along, it adds an extra spike to that rising baseline. the impact of multiple bleaching “We’ve always had those spikes, events. It takes around 10 years for but before global warming they faster-growing corals to recover didn’t cause the damage that from significant bleaching, says they do now.” Ove Hoegh-Guldberg of the The sheer magnitude of the University of Queensland in reef makes surveying it difficult: Brisbane. “We could be getting it covers an area bigger than the close to a scenario where the UK, the Netherlands and return time for bleaching is Switzerland combined. Hughes actually shorter than the recovery initially focused aerial surveys on the northernmost section, which “We’ve always had spikes in sea temperature, but was hardest-hit. He concluded before global warming the recently that around 95 per cent damage wasn’t like this” of it had been severely bleached. “It was the saddest research trip of my life,” says Hughes, who is period, and that would be a recipe yet to find a southern boundary for ever-declining coral cover.” to the affected area. “It’s clear that Indeed, a study published last this bleaching is much more week found that the reef is set extensive than we thought.” to become more vulnerable to In 2002, just 18 per cent of bleaching as rising temperatures reefs in the Great Barrier Reef – cripple their defence mechanisms 120 in total – were badly bleached. (Science, doi.org/bfc5). This year, well over 500 reefs “The amount of coral being have been affected. “This is much affected by this year’s bleaching more severe than anything we is mind-boggling,” says Lyle Vail, have seen before,” says Hughes. one of the directors of the Lizard It could be another four to six Island research station. “You see weeks before we get a full picture corals that you’re familiar with, of how much coral has been lost. have swum with and that you Researchers are also studying know, and now they are dying.”

–A pale shadow of itself–

With soft corals, which lack the skeleton of hard corals, only bare rock is left once they’re gone. “You’d never even know they were there,” Vail says. “It’s devastating.” Later I dive amid coral that’s now perishing before our eyes. A single word is enough to describe our emotions as we head back to base: heartbreak. It’s hard to imagine how the reef can fully bounce back. “Coral cover on the Great Barrier Reef could look very different 10 years from now,” says Hoegh-Guldberg. He highlights the fact that half of this cover has been lost in the past 30 years. For conservationists, the only potential solace is that bleaching could bring home to everyone just what profound effects climate change is having on the natural world. Hoegh-Guldberg predicts another 20 per cent decline in the Great Barrier Reef over the next 10 years if we continue on this path. “If we don’t take aggressive action on climate change over the next decade, it will essentially mean the end of coral-dominated paradises,” he says. ■

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IN BRIEF Ocean pollutants break cells’ defence

Rattlesnakes seen planning attack by clearing strike path IT’S a premeditated attack. Deadly rattlesnakes seem to be planning attacks by clearing a strike path in advance. Northern Pacific rattlesnakes (Crotalus oreganus) have been filmed manipulating vegetation near the burrows of ground squirrels for the first time. Breanna Putman and Rulon Clark at San Diego State University in California recorded two instances of the behaviour at the Blue Oak Ranch Reserve in California’s Santa Clara County. The snakes checked the area for signs of prey and, once they had identified a burrow, forcibly jerked their heads and necks to move surrounding grass. They then

proceeded to wait for their prey in an ambush spot for up to 3 hours (The Southwestern Naturalist, doi.org/bd8n). One of the snakes was seen eating a ground squirrel later that afternoon, says Putman, but it’s not clear if the clearing behaviour played a role in catching the squirrel. Two related hunting Crotalus species have previously been reported moving vegetation near prey burrows, but this is the first time there’s video evidence. Birds and mammals are known to use clever foraging tricks, but most snakes haven’t been seen doing such things. “Perhaps the snakes are modifying their habitat to try to increase their hunting success,” says Putman. “They’re just cool creatures that we take for granted. They actually have behaviours that we once thought were only exclusive to mammals and birds.”

Saturn probe hoovers up stardust CATCH a fallen star. The Cassini spacecraft orbiting Saturn has picked up three dozen specks of interstellar stardust, a find that will help astronomers understand how bits of exploded stars are reborn in new star systems. Though mostly cold and empty, interstellar space contains wisps of gas and fine particles of dust that were released in the fiery deaths of giant stars. Similar in

size and composition to grains of sand, the dust particles are a record of the heavy elements that determine the chemical make-up of new stars and galaxies. “They are of fundamental importance to understanding what primordial ‘bricks’ we come from,” says Nicolas Altobelli of the European Space Agency in Madrid, Spain. He and colleagues have used the dust-analysing

instrument on Cassini to find a record 36 particles, mostly made of magnesium, calcium, iron, silicon and oxygen. The particles were heavily weathered, which suggests they underwent major changes while in interstellar space, Altobelli says. Current wisdom says that pristine grains are battered by the process of star and planet-forming, but the new results suggest part of this process happens earlier, he says (Science, doi.org/bd8g).

THERE’S something fishy going on. We suspected ocean pollutants were getting into our food, now we also know they impair our cells’ ability to expel toxins. Amro Hamdoun and Sascha Nicklisch at the University of California at San Diego studied 37 pollutants and their effect on P-gp, a protein in cell membranes that recognises harmful molecules and boots them out. In experiments on yeast cells expressing the mouse P-gp protein, 16 of the chemicals stopped it from working (Science Advances, doi.org/bd9b). Ten of these chemicals were previously found in humans, implying they are in the food chain, now the new study detected nine of them in tuna caught in the Gulf of Mexico. “P-gp is incredibly important for eliminating a wide range of drugs and toxins,” says Hamdoun. “These widespread pollutants can inhibit this defence system.”

Doughnut seen circling black hole REALLY, it won’t taste good. We have for the first time imaged one of the doughnuts of dust long thought to encircle some supermassive black holes. The black hole at the centre of an active galaxy feeds on a circling disc of gas. This disc can be bright enough to outshine the entire galaxy, but some seem to be obscured by a “torus” of dust. Santiago Garcia-Burillo of Spain’s Madrid Observatory and his colleagues have used a radio telescope array in Chile to image the torus of NGC 1068, a galaxy 50 million light years away. Although it is among the brightest and nearest active galaxies, its torus still appeared tens of thousands of times smaller than the moon (arxiv.org/abs/1604.00205). 23 April 2016 | NewScientist | 15

IN BRIEF

BILL CURTSINGER/NGS/GETTY

EVERY scar tells a story. Whales often have crater-like wounds, but we didn’t know for sure what has been attacking them. Now, an analysis of more than 1700 whale carcasses collected at Donkergat whaling station in South Africa in 1963 confirms that the bites come from the prime suspect – cookiecutter sharks (pictured below). Nicknamed “demon whale biters”, these elusive sharks (Isistius species) usually live in tropical waters. The half-metre-long sharks are thought to rise up from depths of 1000 to 4000 metres to take chunks out of whales. One sei whale carried 138 unhealed bites from the sharks (PLoS One, doi.org/bd8k). The data included how fresh the wounds were and where whales were caught, so the team could discern seasonal trends in biting. “We found that whales are bitten regularly during the [southern hemisphere] autumn, winter and early spring,” says co-author Theoni Photopoulou of the Centre for Statistics in Ecology at the University of Cape Town. This indicates that by mid-spring, the whales had migrated away from the shark-filled area. What’s more, the relatively few fresh bites on maturing sperm whales suggest they spend less time at latitudes where the sharks live than mature whales do.

16 | NewScientist | 23 April 2016

‘Thin’ hormone could fight diabetes and obesity OVERLOOKED no longer. A newly discovered natural hormone could help us to fight diabetes and obesity. Atul Chopra at the Baylor College of Medicine in Houston, Texas, and his team analysed the DNA of two people with a rare disease called neonatal progeroid syndrome (NPS), one symptom of which is unhealthily low levels of fat. The researchers discovered that they were missing a hormone called asprosin. “Asprosin is released by fat cells and goes to the liver, telling it to

immediately release glucose into the blood,” says Chopra. When blood glucose levels rise, production of the hormone is switched off. Because the two people with NPS lack this mechanism for boosting glucose levels in their blood between meals, they often feel lethargic (Cell, doi.org/bd8m). Diabetes researchers are intrigued. “The fact that asprosin hits the liver and causes overproduction of glucose, a key factor in type 2 diabetes, makes it even more interesting,” says Alan

Cherrington of Vanderbilt University in Nashville, Tennessee. Chopra says that an antibody to block asprosin could be given to people with diabetes to reduce blood glucose levels. Asprosin may also play a role in weight gain. While people with NPS are extremely thin, the team also found that obese people have twice as much asprosin in their blood as people who are not obese. “Obesity will be the focus of our next study,” says Chopra. “It’s likely that as fat levels go up, asprosin goes up too,” he says. ESO/APEX/ATLASGAL CONSORTIUM/NASA/GLIMPSE CONSORTIUM/ESA/PLANCK

Sharks rip chunks out of whales

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Muddled-up history makes us ‘psychic’ BAD news for believers in clairvoyance. Our brains muddle our mental timeline, letting us feel we can predict things that in reality have already happened. Adam Bear and Paul Bloom at Yale University asked people to look at white circles on a screen and silently guess which one would turn red. Once a circle had changed colour, the participants reported whether or not they had predicted correctly. The reported accuracy was significantly better than expected by chance, indicating that the volunteers were either psychic or had unwittingly played a mental trick on themselves. To find out which, Bear and Bloom placed different delays between the white circles’ appearance and one of the circles turning red, ranging from 50 milliseconds to 1 second. The reported accuracy was highest when the delays were shortest (Psychological Science, in press). This suggests the appearance of the red circle was influencing decisions still in progress. “We are essentially zombie agents,” Bear says, “under the illusion that we’re always aware of why we’re doing what we’re doing.”

Wispy dwarf in Milky Way’s thrall THE galaxy’s empire has a new colony – a dwarf galaxy larger than nearly all the other satellites of the Milky Way. About four dozen known galaxies orbit our own. Now, Gabriel Torrealba at the University of Cambridge and his colleagues have found a new galaxy about 380,000 light years away in the Crater constellation. “It’s the fourth largest satellite of the Milky Way,” Torrealba says. Named the Crater 2 dwarf, the new galaxy is not apparent to human eyes as its stars are so spread out, although some stars within it are

visible. The team were only able to find it this January by using a computer to look for unusually dense clumps of stars in data from images taken by a telescope in Chile. Most galaxies don’t have defined edges, so astronomers sometimes express a galaxy’s size in terms of its “half-light diameter”, which encloses the brightest part of the galaxy and emits half of its light. The Crater 2 dwarf has a half-light diameter of 7000 light years – which, if we could see it, would look twice as big as the full moon (arxiv.org/ abs/1601.07178).

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Signed, sealed... undeliverable?

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ANALYSIS UN CLIMATE DEAL

Four months on from the Paris climate deal, Michael Le Page looks at how likely it is that countries can keep to the promises made THIS week, world leaders will go to the UN headquarters in New York to sign the climate change agreement they thrashed out in Paris at the end of last year. The ceremony is largely symbolic: the deal doesn’t formally come into effect until 2020. What happens in the meantime is crucial. In December countries agreed to limit global warming to less than 2 °C above pre-industrial temperatures, the ceiling deemed necessary to avoid the most serious consequences of warming. Yet what countries have proposed to do as part of the Paris deal will at best limit warming to around 3 °C by 2100. If we are serious about limiting it to 2 °C and avoiding the far greater effects on weather extremes and sea level rise predicted to happen with that extra 1 °C, they need to do much

DEAL OR NO DEAL It’s set to be the largest one-day signing of any international agreement. Around 150 leaders are expected to sign the Paris climate change agreement on 22 April . Putting pen to paper is just the first step, though. Each signatory also has to formally approve, or ratify, the deal in their parliaments. Only Switzerland, Fiji, Palau, the Marshall Islands and the Maldives have done this so far. The deal comes into force only when 55 countries representing at least 55 per cent of greenhouse emissions have ratified it. Even when it does come into effect, it will remain essentially voluntary. The deal legally obliges countries to set their own

18 | NewScientist | 23 April 2016

the Paris meeting, scientists at the more, and do it now. Global Carbon Project predicted a The good news is that the 0.6 per cent fall in emissions in world’s largest emitter of carbon 2015 based on preliminary data. dioxide, China, looks like it has Now the actual numbers are in, got the message. Thanks to and they suggest that emissions China, global CO2 emissions have flatlined after years of rampant in 2015 were flat rather than growth. So are we reaching a “To have a chance of limiting crucial turning point, or are warming to 2 °C, global delegates effectively signing up emissions need to peak by to an agreement that everyone 2020. This is very unlikely” knows is doomed to fail? On the surface, there are reasons to be optimistic. After falling, Pep Canadell, director of a slight fall following the 2007 the Global Carbon Project, told financial crisis, global CO2 New Scientist. Still, no growth is emissions from fossil fuels and much better than fast growth. industry grew rapidly over the Global emissions figures following decade, at a rate of should be treated with caution, around 2.4 per cent per year. But however, as they come with over the past two years emissions big uncertainties and some have stabilised despite continued countries’ figures are unreliable – economic growth. or non-existent. In a study released just before What we can measure with certainty is the level of CO2 in the atmosphere. Alarmingly, it increased by a record 3 parts per targets for limiting emissions million (ppm) in 2015 and looks between 2020 and 2030, but not to set to rise even more this year, meet them. It was structured this way with some readings at Hawaii’s to allow US president Barack Obama Mauna Loa monitoring station to ratify it using his presidential approaching 410 ppm last week. authority rather than requiring a vote This rise doesn’t necessarily of the Senate – unlike the 1997 Kyoto mean the emissions figures are protocol, which was signed by Bill wrong. Even if emissions really Clinton but never ratified by the US. have flatlined, this trend will be The Kyoto protocol didn’t come obscured by the noise in the into effect until 2005, and the 2012 system – the natural year-to-year Doha amendment has yet to be variations in how much CO2 gets ratified by enough countries (and soaked up by the land and oceans. may never be). Things look more The record growth is partly due hopeful for Paris: China and the US to the now fading El Niño, for have indicated their desire to push instance, which boosts emissions things forward, perhaps enabling the by causing more fires, among deal to come into force in 2017, three other things. years earlier than envisaged in Paris. Canadell estimates that global emissions would have to remain

flat for a decade or so before the trend becomes apparent in terms of levels of CO2 in the atmosphere. This isn’t likely to happen any time soon as we haven’t yet reached peak global emissions. True, China’s emissions – once growing at 8 per cent a year – have slowed to almost zero thanks to declines in manufacturing and efforts to reduce air pollution, says Glen Peters of the Center for International Climate and Environmental Research in Norway. And with China shifting its economy from exports to services, few expect this rapid growth to return. But that doesn’t mean China’s emissions have peaked: its appetite for oil and gas is still growing. Despite that, its emissions may peak before 2030 – ahead of the schedule China put forward in Paris. The bad news is that to have a good chance of limiting warming to 2 °C, global emissions need to peak earlier, by around 2020.

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SINCE PARIS, THREE REASONS TO... ...BE CHEERFUL COOL TO BE ELECTRIC Hundreds of thousands of people signed up to buy Tesla’s latest electric car within a week of its unveiling in March. If electric cars become more desirable than fossil-fuel guzzlers, they could transform the car industry. COLD SHOULDER FOR COAL China, India, Indonesia and Vietnam have plans to build nearly 2000 coal power plants between them – but a recent report concluded that most of these will never be built. This week, China told 28 of its 31 mainland provinces not to approve any more coal plants. RENEWABLES TAKE OFF Investment in renewables rose to a record $289 billion in 2015, and more renewable energy capacity was added than conventional sources for the first time, according to a UN report.

–Will Plan A work?-

With the emissions of countries like India and Russia still climbing sharply, that seems extremely unlikely. And it’s not just about CO2. Levels of two other potent greenhouse gases, methane and nitrous oxide, are still rising fast. Farming is the

main source of both: adding fertiliser makes soils emit nitrous oxide, and livestock belch out methane. In fact, farming emissions are nearly as large as fossil fuel emissions, Canadell says, if the warming potentials of methane and nitrous oxide

On the up Each year, the sources of CO2 to the atmosphere outweigh the sinks, causing levels to rise overall

CO2 rise = 16 gigatonnes per year

Fossil fuels

Land use change Geological resources

Annual global change averaged over 2005-2014

11

Land absorption

9.5

Ocean absorption

SOURCE: GLOBAL CARBON PROJECT

3.4

33 Gt/yr

emissions are added to that of CO2 emissions caused by the switch in land use from forest to agriculture. Put another way, even if we stopped using fossil fuels tomorrow, we would still have a big greenhouse gas problem. It’s a really tough nut to crack because we can’t stop growing food. That makes it even more urgent to slash fossil fuel emissions as fast as we can. Just about everyone agrees on what is required to do it: make countries pay for emitting carbon. Getting countries to agree a common carbon price – and penalising those that don’t enforce it – is a much better approach than focusing on targets for limiting emissions. What we need is leadership from a big player. Bernie Sanders has pledged to introduce a carbon tax if he wins this year’s US presidential election. That could be a game changer – but just like keeping to 2 °C of warming, that’s an almighty big if. ■

...DESPAIR DARKENING CLOUDS Every tonne of carbon dioxide we put into the atmosphere may produce more warming than we thought. A study out earlier this month suggests clouds may not whiten as much as had been estimated as the world warms, meaning they will reflect less heat. SHRINKING ANTARCTICA Sea level rise over the next century may be double previous estimates. An improved computer model that includes processes such as the collapse of ice cliffs is projecting much faster ice loss in Antarctica than previously thought possible. CHEAP OIL Low oil prices may slow the transition to renewables, the International Monetary Fund warned this week. Lower oil prices have discouraged investment in hard-to-extract sources such as tar sands but will also make it harder for renewables to compete on price. 23 April 2016 | NewScientist | 19

COMMENT

Motion picture sickness Andrew Wakefield’s film trying to prop up his discredited linking of MMR vaccine to autism is one for conspiracy theorists, says Paul Offit

ANDREW WAKEFIELD, the former British doctor who erroneously claimed MMR vaccine causes autism, has reinvented himself as a documentary maker. Vaxxed: From cover-up to catastrophe is the resulting film. It sparked a storm of criticism for Robert De Niro’s Tribeca festival in New York, which backtracked on plans to premiere it. It has since been shown elsewhere in New York and in Florida. I have now seen Vaxxed and it should come with a warning – this last-gasp attempt to prop up a thoroughly discredited idea is a threat to the health of children. The film does come with a lot of baggage. Wakefield first sparked a risky flight from child vaccination with a paper in The Lancet in 1998 making his claim about the measles-mumps-rubella shot. This was based on eight children who developed autism

within a month of receiving MMR. Wakefield suggested a series of improbable medical events that lacked evidence to back up his conclusion. The paper was fully retracted in 2010 and Wakefield struck off as a doctor. Since 1998, more than a dozen controlled studies have found no evidence that MMR causes autism. Unfortunately, it’s been easier to scare people than to unscare them; hundreds of thousands of UK and US parents refuse to give their children the MMR vaccine, with measles outbreaks and deaths as a consequence. Although Wakefield has been marginalised by the medical and scientific communities and his hypothesis totally debunked, in Vaxxed he tries a new tack. The film claims he is the victim of a cover-up, saying a paper by the US Centers for Disease Control and Prevention (CDC) in 2004

The clap trap Do STIs solve the enduring mystery of human monogamy, wonders David Barash MONOGAMY is desirable in many ways, but it is not the default mating system of our species. Polygyny, in which a male mates with numerous females, is. There is much evidence for this which, in turn, leads to a mystery: why did monogamy take hold? The latest explanation relies on a mathematical model showing 20 | NewScientist | 16 April 2016

how monogamy could have led to a selective advantage for larger communities practising it. Two factors are vital: sexually transmitted infections and penalties for polygyny (Nature Communications, doi.org/bd8d). The model assumes that polygyny exposes men to greater risk of STIs and thus reduced

fertility. That would allow monogamist groups to outcompete polygynous ones. But this is far from the final word. For one thing, it relies on natural selection at the group level – very controversial among evolutionary theorists. And, while its authors find that group size and monogamy correlate positively, which fits the STI hypothesis, other, more plausible explanations can be invoked. Most notable among them,

“Monogamy may be a tradeoff in which males with power give up advantages to placate excluded ones”

at least for the prevalance of monogamy in modern Western society, is the fact that in a species with an equal sex ratio, polygyny results in many sexually and reproductively excluded males who are liable to be socially disruptive. Monogamy may have developed as a trade-off in which the powerful gave up some or all of their mating advantages for social peace. Thus, by permitting – even mandating – monogamy, modern societies may benefit women, children and most men. In addition, monogamy facilitates male involvement in child-rearing by increasing a man’s confidence that he is the

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Paul Offit is professor of paediatrics in the division of infectious diseases at the Children’s Hospital of Philadelphia, and author of Autism’s False Prophets: Bad science, risky medicine, and the search for a cure (Columbia University Press)

father. This is important, because young humans need a lot of parental investment. What’s more, polygyny often harms women’s reproductive success because of co-wife conflict. The STI idea also assumes women have no say in marriage and mating; experience says otherwise. Where, then, are we? It seems easy to explain monogamy: there are lots of hypotheses, but as yet, no definite answers. ■ David Barash is professor of psychology and an evolutionary biologist at the University of Washington, Seattle, and author of Out of Eden: The surprising consequences of polygamy (OUP)

BRIEFING Sex genetics

SOPHIE CHIVET/AGENCE VU/CAMERA PRESS

misrepresented data on a small subset of African American boys. Wakefield claims there was a statistically significant association between MMR and development of autism in these children. His case is supposedly made by a CDC whistleblower involved in the study. There are problems with this. We never see the whistleblower, only hear his voice. This raises questions about whether he knew he was being recorded and how his statements were used. And the real reason for the finding is never given in the film. African American boys were less likely to have had the MMR vaccine than their Caucasian peers. If an African American boy was diagnosed with autism, he couldn’t get support services until vaccinated. In other words, MMR didn’t cause autism. Rather, the diagnosis of autism caused them to get the vaccine. That Wakefield claims to be the victim of deception is ironic. Perhaps Vaxxed will yet win an award, for Most Outrageous Conspiracy Theory. ■

–Your genes or mine?–

Isthereagenefor losing your virginity? A large genetic study has found areas of the genome linked with the age at which people have sex for the first time. Wait, what? We’ve found the virginity gene? Not exactly. The study, which involved analysing the genomes of people in the UK, US and Iceland, found 38 regions of DNA that correlate with the age at which people first have sex (Nature Genetics, DOI: 10.1038/ng.3551). So if parents had their child’s genome sequenced it could predict when they might first have sex? No, we’re not slaves to our genes in this matter – together these regions account for only a quarter of the variation in virginity loss: not much compared with height, say, where genes account for about 80 per cent of the variation. When it comes to losing your virginity, other factors have much more influence. What would those other factors be? This study didn’t investigate that but other work suggests teens are more likely to start having sex earlier if they

come from poorer families, if they are not religious, and if their parents have little involvement in their lives. But isn’t it surprising that genes have any influence at all? Perhaps – losing our virginity certainly feels like a highly conscious, personal decision for most of us. But assuming the act is fully consenting, it makes sense that genes play a role: after all they influence many aspects of our personalities and thus how we behave.

“One gene is involved in brain signalling. The earlysex variant has been linked with riskier behaviour” One of the genes, called CADM2, is for a molecule involved in nerve signalling. The early-sex variant has been linked with riskier behaviour and poorer mental abilities such as attention. When do most people first have sex? In many Western countries the average age is about 16. This has fallen since 1990 when it was 17 for boys and 18 for girls in the UK. Here,

about a third of teenagers have sex before they are 16. Tempting though it is to think so, none of the DNA regions identified should be thought of as a “gene for losing your virginity early”: each is linked with having sex only a few weeks earlier than you might if you carried an alternative variant. Hasn’t the average age of puberty been falling too? In the mid-19th-century, the average age girls in the US first had periods was 18. By 1980, it had fallen to 12 – probably because of improved nutrition – where it seems to have levelled off. The other genes the researchers found appear to be acting on age of first sex by affecting the age at which people go through puberty. Again this makes sense – it’s unsurprising that children who go through puberty earlier would be interested in sex earlier too. Is it the end of the world if children are having sex earlier, as long as it’s consenting? Some people claim that earlier first sex causes problems in later life such as relationship difficulties and even depression. Studies do show a correlation with riskier sex (such as unsafe sex and drunk sex) later on but are these directly caused by earlier first sex? A 2011 study of identical twins suggests not, and that a third factor – possibly impulsiveness – causes both. Clare Wilson ■ 16 April 2016 | NewScientist | 21

TECHNOLOGY

Dating by numbers Some sites use algorithms to match people looking for love – “metadating” goes a step further and lets you pore over a potential suitor’s data, finds Aviva Rutkin

REX/SHUTTERSTOCK

ONE Saturday night last year, 11 people went looking for love. Like countless speed daters before them, they met in a room draped with curtains, the lights on low. In one hand they held traditional glasses of bubbly, but in the other were sheets of paper they had filled with their personal data. This twist on speed-dating was part of an experiment run by a team at Newcastle University in the UK. They wanted to know what would happen in a world where instead of vetting potential dates by their artfully posed selfies or carefully crafted datingsite profiles, we looked at data gathered by their computers and phones. As use of data-gathering devices increases, it’s a world that’s just round the corner. The team calls it “metadating”. “There’s a bit of a mismatch between a data led view of the world – which is very dry and

22 | NewScientist | 23 April 2016

mechanical – and how we view they spent time looking over ourselves,” says Chris Elsden, who one another’s anonymised data headed up the project. Elsden and profiles, discussing who they his colleagues want to explore might like in groups. The event other ways we can use data that then took the form of traditional gets collected as we go about our speed-dating, with four minutes modern lives. “Can we give people for pairs to get to know each other. more control over it, make it more The researchers listened as ambiguous or playful?” people described themselves The team recruited their speed using the “language of data”. They daters on social media and via read out their numbers, compared posters around their university stats and even complimented one campus. A week before the event, another on their data. Where the participants were sent a form people had been allowed to list to fill out. It asked for a host of “One dater graphed their specific numbers: shoe size, the Fitbit steps, another drew farthest distance they had a pie chart of the furniture travelled from home, the earliest in their house” and latest times of day they had sent an email in the past month, their heart rate as they filled out whatever they liked, they had the form. It also left blank spaces picked very different types of for people to add whatever data information to portray themselves. they wanted. One scrupulously graphed their Seven men and four women Fitbit steps. Another recorded took part. To kick off the evening, what they ate for breakfast, lunch

and dinner. Others chose to be playful. One drew a pie chart of the different types of furniture in their house. Someone added: “Miles run this week: 0”. The team will present a review of the project next month at the ComputerHuman Interaction conference in San Jose, California. So much of our data is in the hands of large companies that it can make people feel powerless, says Jessa Lingel at the University of Pennsylvania. Elsden’s event flips that on its head. “Offering a way for people to feel like they have some control, or can be creative or thoughtful about the data they’re producing, is really important,” Lingel says. She also thinks metadating plays with an idea we have about what romance in the future might be like. Data-driven algorithms already match people on dating sites like OkCupid. Other dating start-ups like Genepartner try to push the envelope by matching people according to genetics. It’s not hard to envision a site that digests numbers from your self-tracking apps and search history, then spits out people it thinks you might be attracted to. But Elsden doesn’t think metadating should replace popular dating apps. “We’re not suggesting your ideal match would be somebody who gets up at the same time,” he says. He thinks it might open the door to a new sort of social media – an “Instagram for data” that lets you collect your stats, manage them with editing tools or filters and share them with your friends. Still, at least one couple hit it off swapping stats that Saturday in Newcastle. As far as Elsden is –Likes walks on the beach, and stats– aware, they’re still together. ■

CLOVER/PLAINPICTURE

For more technology stories, visit newscientist.com/technology

Electronic skin turns you into a digital display

They suspended the pieces of meat in a water tank and found that an ultrasonic signal passed through both types of meat at speeds of up to 30 megabits a second. That is 1000 times faster than existing implants, which send radio signals through tissue at a maximum of 50 kilobits a second. “You could stream Netflix through the pork loin,” says Singer. “For high-definition video, this is more than sufficient,” says Akram Alomainy at Queen Mary University of London in the UK. Alomainy thinks the technology could be particularly useful for

FORGET smartwatches. A super-thin electronic skin can turn the back of your hand into a digital display. Similar e-skins have been made before, but at just 3 micrometres thick this is the thinnest yet. It is also more durable. Made by Takao Someya at the University of Tokyo and his team, the e-skin can be laid over actual skin anywhere on the body. Looking like a layer of plastic food wrap, it is flexible enough not to break when you move. The display also works for longer than other devices, using LEDs that last for several days. The bright display works with less power than existing e-skins (Science Advances, DOI: 10.1126/sciadv.1501856). Connected up to sensors on the body, the e-skin has been used to display a person’s pulse and blood oxygen concentration on their hand. This could be used by people in hospital, for example – or athletes while they are training. But Someya sees a wider range of uses. “A worker will be able to have building plans or an electrical diagram displayed on their skin without carrying heavy devices,” he says. The device uses a seven-segment LED to display a single digit or letter (see photo, below). The team is now working on a display that can show far more information. Super-thin plastic sheets could replace smartphones, says Someya. Sandrine Ceurstemont ■

“The wireless signal passed through meat at speeds fast enough to stream high-definition video” wireless endoscopy, in which a person swallows a pill that broadcasts a video feed from inside their digestive tract. At the moment, wireless endoscopy requires a laptop-sized device cStreaming through steak– outside the body to pick up the feed. A system that used ultrasonic waves to transmit would be far less cumbersome. But Alomainy says he would first like to see the team send a signal through multiple layers of organs. “We don’t just have one organ in our body,” he says. Illinois at Urbana Champaign. “A liver has different properties So his team turned to ultrasound. from the kidney or the stomach.” Singer has spent years building He thinks the data might not ultrasonic systems for the navy move as quickly when travelling and suspected that a similar through different types of tissue. approach would work well in the The meat-comms team plans body. “You’re a big bag of salt to test the approach with real water,” he says. “Communicating medical implants or living tissue, in the ocean and communicating but the initial results already in your body are very similar.” suggest some exciting future Ultrasound is sometimes possibilities, says Singer. Software used to perform surgery without updates could be beamed directly having to cut open the body. High- to medical implants without the intensity sound waves focused need to remove them surgically. on a tiny area can burn away One day, we could have wireless unwanted tissue without harming networks inside our bodies, with the surrounding area. But Singer an implant in our gut sharing wanted to use it to send data. information with one in our Singer and his colleagues tested liver. “We wanted to show that the idea using two different types it was possible,” says Singer. Aviva Rutkin ■ of tissue: pork loin and beef liver.

YOUR data rate is about to get a meaty boost. Researchers have fired a wireless signal through slabs of pork and beef at speeds fast enough to transmit highdefinition video. The technique, nicknamed “meat-comms”, could help doctors interact with medical devices implanted in our bodies. Existing implants use near-field radio to communicate with the outside world. But this does not travel well through soft tissue. Ramping up the power to improve the signal is dangerous, as it heats up the tissue it passes through. These limitations have stopped us developing medical implants that can send and receive useful amounts of wireless data, says Andrew Singer at the University of

THE UNIVERSITY OF TOKYO, SOMEYA GROUP ORGANIC TRANSISTOR LAB

Ultrasound beefs up wireless for implants

–Handy read-out– 23 April 2016 | NewScientist | 23

TECHNOLOGY

ONE PER CENT

Let your mind wander Virtual reality tourism has arrived. Hal Hodson heads into the jungle

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striking places without leaving authorities do let tourists visit, your living room. but unless they take the expensive CTO and founder David helicopter they must hike through Finsterwalder made the Jaguar the jungle for three days. “They Paw Temple reconstruction just want to let tourists go there, but two weeks ago. After flying to they don’t want to have roads,” Guatemala City, then catching a says Finsterwalder. “With roads local flight to the small town of you will have loggers, and this is Flores, he and a team from the the last part of Guatemala where Global Heritage Foundation took the rainforest is really complete.” a 30-minute helicopter ride into Instead of bringing people to the jungle. Armed with a highsuch places, his small start-up is definition still camera and a tape bringing the places to people. The measure, they stayed long enough to take a few hundred photos and “The Mayan ruins are three days walk from the nearest record key measurements. road – so I’m exploring They then stitched it all together them from San Jose” into a virtual reality for anyone to explore. Most people who visit the Mayan ruins are just one of the real site are archaeologists – destinations on the company’s Finsterwalder’s original books. I also explore the ruins occupation. The Guatemalan of Castle Hohenrechberg in southern Germany and gaze up at the ceiling of 10th-century Cluny Abbey in Saône-et-Loire, France. Then I poke around in a room of the abandoned Beelitz-Heilstätten hospital, where Adolf Hitler recovered after being wounded at the Battle of the Somme in 1916. I can’t touch the places I visit, but I can teleport around them with the click of a button. Pointing a controller to where I want to go, I zip through the environment. Stone walls blur past as I zoom to the top of Hohenrechberg. There’s a broken beer bottle on the floor and I can see the brand. “The photorealism hooked me,” says media researcher Xárene Eskandar at the University of California, Santa Barbara. “You can look in holes, behind doors and under chairs.” I watch other people step into Finsterwalder’s worlds. “Oh my God, oh my God, this is so cool,” says a woman. She gasps in wonder as she looks up. “I feel –Closer than ever– like I’m really in here.” ■

Licence to mod Think you can improve on the design of your gadgets? Now you can put your skills to the test with RetroFab, a system that lets you customise the controls on devices from TV remotes to toasters. Developed by Autodesk Research in Toronto, Canada, it scans the device and suggests alternative button layouts that you can tweak before 3D printing the results. The new controls can then be fitted over the ones they replace. The developers suggest that RetroFab could be applied to making appliances child-proof.

“It’s a treat to be invited to collaborate on a big cultural project” Whistleblower Edward Snowden teams up with electronic music producer Jean Michel Jarre to record a techno track called Exit

Painting in the gaps UK company Magic Pony has unveiled an AI that attempts to fill in missing parts of an image. Given just a small section of a scene, the system finds rules that describe that part and uses these to devise imagery to complete the picture. It can be also used to fill in details in blurry images, automatically making poor-quality photos or video clearer.

AUTODESK RESEARCH

AGE FOTOSTOCK / ALAMY STOCK PHOTO

JAGUAR Paw Temple lies deep in the Guatemalan rainforest, part of the ancient Mayan ruins of El Mirador. Three days walk from the nearest road, it’s almost inaccessible. And yet here I am. I get down on my knees to examine a sculpture of a jaguar, its crannies full of jungle dirt. Dead leaves have collected at its feet. I can see it all, right in front of my face. But my body is back in San Jose, California, at the GPU Technology Conference, with a screen strapped to my face and two motion-tracking cameras watching my movements. I’m exploring the latest destination offered by virtual reality company Realities.io, which lets you visit some of the world’s most beautiful and

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THE BIG THEMES: Explore the anatomy of the brain, how memory works and the origin and purpose of emotions. Learn what sleep tells us about the brain and the future of brain implants. OUR EXPERTS: Morten Kringelbach, Mary Morrell, Andrew Jackson, Peggy St Jacques, George Mather Hosted by Claudia Hammond, psychologist and

presenter of BBC Radio 4’s All in the Mind

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MAIN IMAGE: JOHAN SWANEPOEL/SHUTTERSTOCK

APERTURE

26 | NewScientist | 23 April 2016

Orchid cuckoo bee Exaerete frontalis

APERTURE

Ground beetle Carabus elysii

Jewel longhorn beetle Sternotomis species

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Ready for ultra close-up

Tortoise beetle Platypria melli

“MOST photography these days,” says Levon Biss, “is disposable. We take images without much of a thought process.” He wanted to achieve the opposite. He succeeded, and then some. I’ve never seen insects photographed in such detail as those in Biss’s Microsculpture series. Nor has James Hogan, insect curator at the Oxford University Museum of Natural History, which lent Biss the specimens for the project. Each finished image is a composite of 8000 to 10,000 photographs taken with a microscope lens. Biss cleans the specimen, lights the section he is interested in, then takes a shot. Moving the lens less than a millimetre, he takes another. Finally, he stitches all the shots together into one ultra-high-resolution portrait. No wonder it takes two to three weeks’ work to complete each image. Whole insects have never been seen in this astounding detail, which you can appreciate even more by zooming in on the images available on Biss’s website (see below). “Insects are the most beautiful creatures in the world,” says Biss. “Their variety and splendour is a dream for a visual artist. When viewed at high magnifications, they never fail to surprise.” The images reveal a large range of microstructures: surface sculptural patterns, pigmented scales and hairs of different shapes and sizes. These throw up questions, since we usually think of natural selection in terms of large-scale features such as eyes and wings. One puzzle is the microtexture of beetle wing cases. “Species from wet areas often have a transverse pattern, those from saline habitats a pattern of slightly raised bumps,” says Hogan. One possible explanation is that the microtexture reduces friction, he says. “Levon’s photographs highlight what we don’t know, but for me that is what makes them so fun.” The images will be on show as 3-metre prints at the Oxford University Museum of Natural History from 27 May until 30 October. Rowan Hooper

Photographer Levon Biss microsculpture.net

23 April 2016 | NewScientist | 29

COVER STORY

Life, the solar system and everything F THE 200,000 shards of rock that Mark Harrison has retrieved from Australia since the mid-1980s, only one contained what he was looking for. Two flecks of graphite, each barely the size of a red blood cell. Small, perhaps, but capable of overturning everything we know about life on Earth. Harrison, a geologist at the University of California, Los Angeles, remembers thinking to himself: “By golly, they’re a dead ringer for a biogenic origin.” Biogenic means made by life – but how? These graphite flecks were found in a zircon crystal that had lain trapped deep in the Jack Hills of Western Australia for 4.1 billion years. So they seem to imply our planet was inhabited at least 300 million years earlier than anyone had previously imagined. What’s more, these first living organisms would date from a time before our planet was thought capable of harbouring any life at all. In these early years, Earth was supposedly a molten hellhole racked by volcanism and bombarded by space debris, zinging around a solar system yet to find inner peace. If Harrison’s fossils are all they seem, they wouldn’t only rewrite the history of life and Earth – but the entire solar system’s as well. When it came to explaining how these things all got started, we thought we had it more or less worked out. Some 4.6 billion years ago, a vast cloud of dust and gas in some corner of an unremarkable galaxy began to collapse into a dense ball of matter. As more and more surrounding material was pulled towards it, the temperature and pressure at its

O

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core increased, to the point where nuclear fusion kicked in. This released vast quantities of energy and marked the moment our sun became a star. As the newborn star slowly began to spin, smaller bodies started to coalesce in orbit around it. Close in, vast quantities of water ice were boiled away, leaving only metallic compounds behind to form the smaller rocky planets. Further out, cooler temperatures allowed giant worlds of ice and gas to form. All in a single plane along smooth, nearcircular tracks. It was a nice story, but as further details emerged, it became apparent that this picture was incomplete. For one thing, it struggled to explain the quantity and distribution of the so-called Trojan asteroids, thousands of tiny bodies that chase after Jupiter in its orbit. The Kuiper belt, the icy band beyond Neptune that Pluto belongs to, was equally difficult to justify: many of its bodies orbit at far greater angles to the planetary plane than the conventional picture would allow. Perhaps most perplexing of all, however, was the evidence our cosmic neighbourhood had once been under heavy bombardment. Rocks returned to Earth by the Apollo astronauts suggested the widespread cratering on our own moon was the result of a protracted assault which took place 3.9 billion years ago – a ruction the conventional model found hard to explain. The solution, named after the city in France where it was devised in 2005, was the Nice

NEIL STEVENS

The story of our cosmic origin is all wrong, finds Colin Stuart

ELIZABETH BELL, ET AL./UCLA

Rewriters of the solar system: tiny shards of zircon

model. In this refinement of the traditional story, our solar system’s four giant planets started out much closer together than they are today. This configuration was unstable, leading to hundreds of millions of years of gravitational tussling, during which the giant planets migrated into their current positions, disturbing the millions of tiny bodies littering the ancient solar system. Many fell under Jupiter’s gravitational influence, becoming its Trojan followers, while others settled in the solar system’s outer regions as highly angled denizens of the Kuiper belt. Meanwhile, asteroids in the band between Mars and Jupiter were dislodged from orbit, many going on to collide with the innermost planets. This period of intense activity, known as the Late Heavy Bombardment (LHB), would have left deep craters on the moon and given our fledgling planet a serious knock during the turbulent early stages of its development. The small number of surviving solid rocks from this period have led us to picture early Earth as a fiery world covered in volcanoes bursting through a molten crust. The LHB’s few hundred million years of constant collisions contributed to a nightmarish landscape so extreme that the geological period is known as the Hadean, after the Greek god of the underworld. The existence of life in such a hellscape was considered preposterous. Instead, the first traces of biogenic carbon, dated at 3.8 billion years old, neatly coincide with the time Earth was > 23 April 2016 | NewScientist | 31

BIRGER RASMUSSEN/CURTIN UNIVERSITY

Hellmouth: Australia’s Jack Hills hark back to Earth’s violent youth

finally at peace and the bombardment from outer space had slowed. Hence the excitement if Harrison’s fleck of graphite really is what it appears to be: evidence not only of our planet’s oldest known life form, but one that emerged at an impossible time. His smoking gun was the ratio of isotopes carbon-13 and carbon-12, within the sample. “If you were looking at this carbon ratio today, you would say it was biogenic,” he says. Astonishing as it is, Chris Ballentine from the University of Oxford cautions against getting carried away. “It is one inclusion in one

zircon,” he says. “But this sets the bar for people to find more and really show there was life around back then.” Life or no life, it’s just the latest piece of evidence from the Jack Hills suggesting Earth’s hellish youth was more short-lived than astronomers thought possible. As far back as 1999, geologists uncovered other zircons in this astonishing terrain that indicated part of Earth’s surface had cooled and solidified 4.4 billion years ago. What’s more, measurements of how much oxygen the rocks contained suggested that Earth had been mild enough to support liquid water.

MYSTERY OF THE MISSING PLA AN NET Ever sensed something was missing? Researchers modelling our solar system have. Their best stab at explaining how our cosmic neighbourhood came to be suggests there shouldn’t be four giant planets in the outer solar system – there should be five. In 2011, simulations suggested that without this mysterious fifth planet, intense gravitational interactions in the early solar system would have had disastrous consequences. As the four giants slowly creaked into their current positions, they would have disrupted their smaller neighbours, making the modern solar system all but impossible. But with five giant planets jostling for supremacy, the 32 | NewScientist | 23 April 2016

migration would have taken place quickly enough to leave the innermost rocky planets virtually unharmed. What’s more, one of the quintet would have been slingshotted into the furthest reaches of the solar system, leaving us with the four outermost planets as we see them today. Where exactly did this guardian angel end up? Speculation surrounding the existence of “Planet Nine” has long bubbled under the surface, but earlier this year the excitement finally burst when two astronomers from the California Institute of Technology announced they might have found it. With an orbital radius 600 times greater than Earth’s, this candidate Planet Nine would

take at least 10,000 years to complete a single lap of the sun, making it one of our solar system’s most distant objects. Its existence has been inferred from the unusual clustering of half a dozen small objects beyond Pluto, which would be difficult to explain without a distant planet’s gravitational pull. The logic holds up, but direct observation has eluded us thus far. It would be a remarkable find. Its discovery, while a pain for textbook publishers and quiz show contestants, would support the five-giant scenario for the solar system’s formation. “If Planet Nine exists, that’s where it must have come from,” says Matija Cuk of the SETI Institute in California.

Further evidence that not all was right in the established picture of Earth and the solar system came in 2013, when Judith Coggon, then at the University of Bonn, Germany, was analysing another contender for the planet’s oldest rock – on the other side of the world in Greenland. There she found evidence that Earth contained significant quantities of gold and platinum as far back as 4.1 billion years ago – even though these metals were thought to have been delivered only later by the Late Heavy Bombardment. Yet more contention came last year, when Nathan Kaib from the University of Oklahoma, along with John Chambers from the Carnegie Institution in Washington DC, published the results of their latest simulations of solar system formation. What they found seemed to sound the death knell for the Nice model. In 85 per cent of cases, the inner solar system ended up with fewer than the four rocky worlds it has today. “More often than not you lose Mercury,” says Kaib. Only 1 per cent of the time could they create a solar system that looked like the one we recognise. It would not be the first time the Nice model has been modified to take account of problems (see left “Mystery of the missing planet”), but this was a problem of a different magnitude. “It seems very unlikely that you can get the outer solar system architecture and protect the inner planets,” he says. Kaib has a surprisingly simple solution. The giant planets still migrated, producing the Jovian Trojans and the Kuiper belt, but they did so much earlier – while the innermost planets were still forming. By turning up to the party fashionably late, Earth dodged a bullet. The early migration of the giant planets

“Rewriting our history ym ma ake ake es e the notion of life else ew whe ee ere that much more likely y” would have scattered most of the larger impactors by the time Earth’s formation was complete. That works well, says Zoë Leinhardt, from the University of Bristol, UK. “The latter part of Earth’s formation would have been calmer, as opposed to having formed and then being smacked upside the head.” It’s an appealing theory, explaining not only why the solar system looks the way it does, but how Earth became friendly to life so early. But one final mystery remains. If the giant planet migration happened before Earth and the moon had formed, then something else must

Alternate history To explain fossils 4.1 billion years old, we need to rewrite the solar system’s history along with one of its most cataclysmic events, the late heavy bombardment (LHB)

Old timeline

Planetary migration and LHB

Earth forms

Liffe begins on Earth

Solar system now

Solar system forms

illions of ears ago

4.6

45

4.4

4.3

Hostile to life 4.2

4.1

4.0

3.9

3.8

Solar sysstem forms Earth forms

have been responsible for the craters on the lunar surface. But what? David Minton from Purdue University thinks the answer lies closer to home. “In the Nice model, most of the LHB impactors come from the asteroid belt,” he says. “But the distribution of crater sizes on the moon and the distribution of asteroids don’t match.” Matija Cuk of the SETI Institute agrees. “If the LHB really was just asteroids being thrown at the moon en masse, there should be a lot more big lunar basins, and there aren’t,” he says. Minton believes he might have found an alternative source for the LHB: Mars. He’s still working on the finer details, but he presented the concept to the American Astronomical Society’s Division on Dynamical Astronomy at their meeting in May 2015. One fact working in its favour is that the Red Planet’s northern hemisphere is low-lying and considerably flatter than the highlands in the south. “Many have suggested that’s because the northern area is a giant basin formed by a 2000-kilometre impactor,” says Minton. Debris thrown up by the formation of this so-called Borealis basin could have bombarded the moon, and Earth, 3.9 billion years ago. Cuk has an even more radical explanation. “To me it is not clear at all that there was a spike in lunar bombardment 3.9 billion years ago,” he says. The Apollo samples that led to the assumption were returned from several different sites on the moon, with many

Solar system now

Life begins on Earth

showing evidence of impacts clustered around that time. But Cuk believes the Apollo samples all came from the impact or impacts that formed the Imbrium basin – one of the large, dark patches that makes up the “Man in the Moon”. Rocky shrapnel from this event could have contaminated disparate parts of the lunar surface, meaning that what at first looked like a host of simultaneous impacts might have only been a handful. “The idea of the carpet-bombing of the moon 3.9 billion years ago has gone away,” he says. If you could prove the impacts that caused the cratering on the moon were less of a spike and more of a steady drip, then the Nice model could be

NASA

Revised timeline ne

Plan ne etary migra i ation and LHB

Up for grabs: the origins of the moon’s impact craters

saved after all. Just as crucially, it would have profound implications for conditions on our infant planet. “If the impacts were more smeared out, early Earth wouldn’t have been total hell,” says Cuk. Either way, with relative calmness kicking in sooner in Earth’s history, life could have emerged more quickly to leave its mark in the Jack Hills zircon. “Pushing giant planet migration back earlier would be consistent with what we found,” says Harrison. Future work will look at cementing this idea. Harrison has already identified another graphite inclusion in a separate Jack Hills zircon and will be analysing the ratio of its carbon isotopes within the next few months. If Harrison’s hunch is right, then the life forms we had previously thought of as our earliest ancestors, dating from 3.8 billion years ago, weren’t the beginning of the evolutionary tree at all. Instead life on Earth began hundreds of millions of years earlier, almost as soon as the planet was ready for it. Such a scenario would raise hopes for the speed and ease with which biology can take hold, and of its aptitude for sticking around in an unfriendly cosmos. According to Harrison, “it makes the notion of life elsewhere in the universe that much more likely.” Our revised history could point to a more interesting future. ■ Colin Stuart (@skyponderer) is an astronomy writer and author of The Big Questions in Science 23 April 2016 | NewScientist | 33

BLIND IN THE MIND I can’t visualise things, says Dustin Grinnell. So what’s going on in my head? ONG-DISTANCE relationships aren’t easy at the best of times. But when my girlfriend and I had to move to opposite sides of the US for work, we faced an obstacle that few others do. I couldn’t picture her face. It is the same for landscapes and sunsets, parks and rivers: when it comes to mental imagery, I am blind. At the time, I didn’t think anything of the fact that I couldn’t conjure up a mental image of my girlfriend at will. I have never had that ability, so I didn’t know what I was missing. And it wasn’t as if I have trouble with tasks that you imagine might require such a “mind’s eye”, like navigating around town or recognising friends.

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So I got a shock when I saw a TV interview with Craig Venter, the biologist who created the first synthetic organism. He spoke then of how he attributed his academic success to an unusual way of thinking, using purely concepts with no mental imagery whatsoever. And he says the same thing now: “It’s like having a computer store the information, but you don’t have a screen attached to the computer.” That’s exactly how I feel too – and so my questions began. Why am I different? How do I navigate life without a mind’s eye? Could I ever train my mind to see – and would I want to? I began to investigate and soon discovered that science is starting to find answers. And

ironically, studying people like me is helping to reveal a lot about how our brains process the things we see around us. We have known of the existence of people with no mind’s eye for more than a century. In 1880, Francis Galton conducted an experiment in which people had to imagine themselves sitting at their breakfast table, and to rate the illumination, definition and colouring of the table and the objects on it. Some found it easy to imagine the table, including Galton’s cousin, Charles Darwin, for whom the scene was “as distinct as if I had photos before me”. But a few individuals drew a total blank. Today there is a standard way to probe the acuity of the mind’s eye: the Vividness of

Visual Imagery Questionnaire. It asks people to imagine various scenes and rate the clarity of the mental picture (see “Picture this”, page 37). Surveys show that most people have fairly vivid mental imagery; only 2 to 3 per cent report a completely image-free mind. For a long time, no one gave much thought to what caused this. “It was an academic blind spot,” says neurologist Adam Zeman of the University of Exeter, UK. That changed in 2003, when Zeman got a call from a colleague who said: “I’m sending you a patient because he can no longer imagine.” The man was a 65-year-old building surveyor known as MX who reported losing his mind’s eye after heart surgery. Zeman decided to find out what was going on inside MX’s head.

DAVID REHOR/MILLENNIUM IMAGES

Tony Blair’s eyes

How clear is your mind’s eye? This puzzle is used as a test for mental imagery. If you can solve it quickly, you probably have a strong mind’s eye. To begin, stare at this shape until you can remember it. Then turn the page and find three similar objects. Which ones are rotated versions of this shape, and which are not?

a

We have a good idea how creating a mental image usually works. When you see a real object, the information captured by your eyes and fed to the brain activates a pattern of neurons unique to that object: a chair has one distinct pattern, a table another. MRI brain scans show that when you imagine a picture of that object, the same neural pattern lights up, just slightly less strongly than when you are actually seeing it. “Picturing an image in your mind’s eye is like running the system from the top down, rather than from the bottom up,” says Zeman. To find out how MX’s brain worked, Zeman put him into an MRI scanner and showed him pictures of people he was likely to recognise, including former UK prime minister Tony Blair. The visual areas towards the back of his brain lit up in distinctive patterns as expected. However, when MX was asked to picture Blair’s face in his mind’s eye, those areas were silent. In other words, the visual circuits worked when they had a signal from the outside world, but MX couldn’t switch them on at will (Neuropsychologia, vol 48, p 145). But then came an unexpected finding. Even though MX couldn’t form a picture of Tony Blair, he could handle tasks that would seem to require one – stating Blair’s eye colour without seeing a picture of him, for example. He also aced other tests, such as imagining standing in his own home and counting its windows. Soon after Zeman published his results, he heard from another 21 people who said they had this condition, which he called aphantasia. However, unlike MX, they claimed to have had it from birth. A battery of cognitive tests soon confirmed they had the condition and that, like MX, they had no problem getting on with life, including tasks that might seem impossible without a mind’s eye. It might sound paradoxical, but for me these “tests of visual imagery” aren’t difficult to complete without a mind’s eye. Take the > 23 April 2016 | NewScientist | 35

window-counting test. I don’t experience a mental image of my house, but rather an awareness of being there. Venter says it is the same for him. He doesn’t have to “see” events to relive them, he says. “There are different ways of storing visual information than just the picture.” To find out about these, I spoke to Stephen Kosslyn, a cognitive neuroscientist at the Minerva Schools university in San Francisco. He says visual imagery is not constructed in just one way in the brain. There are separate circuits for things like shape, colour and spatial relationships, among much else. It seems as if not all my circuits are disabled. I have no trouble answering some of the test questions Kosslyn ran me through, like, “Which is darker green: spinach, or the outside of an avocado?” But others were tougher. Kosslyn asked me: “In the upper-case letter ‘A’, what shape is formed by the enclosed region?” After concentrating for a few moments I replied that it was a triangle, and Kosslyn asked me how I had arrived at it. It almost felt as if I was drawing the letter, I said. Kosslyn thinks the drawing sensation gives us a clue as to how aphantasics deal with apparently pictorial information. He suggests that to complete these tasks I am piggybacking on neurons involved in controlling physical movements rather than using the visual brain circuitry. Kosslyn once had a patient who had a stroke that damaged the visual areas of her brain and left her blind. She too could still complete what might be considered visual tasks. When Kosslyn asked her to imagine the letters of the alphabet one at a time and tell him whether they had any curved lines, she could do it perfectly. “But if you watched her,” says Kosslyn, “she was drawing the letters with her fingers.” Zeman agrees this might be how some aphantasics do it. “There are many ways of representing the world beyond the visual,” he says. “You might be able to imagine a letter Which of these shapes is a rotated version of A on page 35? It’s a good test of your mind’s eye, because it probably involves playing with images of the shapes in your mind. (See the end of the article for the solution.)

b

36 | NewScientist | 23 April 2016

because you can see it or because you can imagine making it.” It’s not just that mental pictures aren’t the only way to process “visual” information; they might not even be the best way. Zeman has evidence that points to this. “A surprise is that we’ve been contacted by a certain number of aphantasic artists,” he says. You might assume that artists in particular need a mind’s eye, but perhaps this isn’t the case. Then there is Venter, who sees a connection between his aphantasia and his scientific achievements. “I’ve known many people with photographic memories for facts who can’t even remotely combine them conceptually like I can,” he says. Perhaps not having a

c

mind’s eye forces you to see the world differently, resulting in an unusual eye for art or alternative modes of thinking. MX provided more concrete evidence of the unique skills of people who have aphantasia. When Zeman first tested him, he gave him a classic test of proficiency with mental pictures. The challenge was to work out which images are the same as a guide image, only rotated, and which are not (see diagram, page 35). The greater the rotation, the longer it takes most people to perform the mental gymnastics and work out if there is a match. The theory goes that people rotate a mental image in their heads, and the more they have to manipulate it, the longer it takes

d

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to solve the task. MX apparently wasn’t doing that – yet he completed the challenge faster than average. We still don’t know exactly how people with aphantasia do what they do, but the idea that various brain circuits can be used to process visual information is gaining traction. Zeman reckons we all use different circuits to some extent. It’s just that most people with a functioning mind’s eye rely predominantly on visual circuitry. But could some of us be better than others at using non-visual circuits to process visual information? And would this give people an edge at certain tasks and jobs? We don’t have enough evidence to answer that question yet. But Zeman has been running a large experiment probing these areas and results are expected next month. Zeman has now encountered many people with little or no mind’s eye. Like me, many of them didn’t grasp that they were missing anything until they heard about aphantasia, and most say they felt only a mild sense of loss. But for some, the condition is distressing. I spoke to one patient of Zeman’s who mourns the ability to conjure up pictures in his head. “I’d love to be able to recall memories of my childhood holidays or my first kiss. It would be like waking up from being blind,” he says. Happily, there are reasons to think such an awakening is possible. For one thing, many aphantasics dream in pictures and some see flashes of imagery under certain circumstances, such as just before they drift

off to sleep. So although they can’t consciously control their mental pictures, the capacity itself doesn’t seem to have vanished. There are parallels with blindsight, says Zeman. People with this condition have no conscious awareness of being able to see, yet can navigate a cluttered room without problems. Zeman suspects that some aphantasics process visual information in similar ways: when mentally counting the windows in their home, they don’t think they are seeing a picture, but they are – subconsciously. For people with no experience of aphantasia, this probably sounds bizarre. Yet the idea has prompted some researchers to think seriously about whether aphantasics are really missing a mind’s eye, or just not noticing that they have one. Stefania de Vito at the University of East London, UK, and Paolo Bartolomeo at Pierre and Marie Curie University, Paris, suggest that aphantasics do retain the capacity to form mental images – they simply believe they can’t. They propose that extreme stress could induce this change, pointing to an 1883 case study of a “Monsieur X”, who developed aphantasia after a period of intense anxiety (Cortex, vol 74, p 334). This probably isn’t the whole story, Zeman thinks, because there are examples of aphantasics who developed the condition when they weren’t overly stressed, including MX. But it does raise a tantalising question for people like me: is aphantasia sometimes reversible? Can a blind mind be trained to imagine pictures?

Mental reset Joel Pearson at the University of New South Wales in Sydney, Australia, has tested exactly that. To get started, he needed an objective way to measure the clarity of people’s mental imagery, a tall order because such tests tend to rely on subjective ratings. In 2008, he found a way. He divided people’s fields of vision so that they saw a set of horizontal red stripes through one eye and vertical green stripes through the other. Under these circumstances, people perceive not a combination of the two patterns but one or the other. At first there’s a 50-50 chance of perceiving either. But when Pearson flashed the stripes in front of people several times he found that, for most people, the probability of perceiving the pattern they had spotted the first time round went up. That is presumably because they had created a picture of the pattern in their mind that primed them to perceive it again. When he tried this on aphantasics, he saw the priming effect in some but not in others. Conclusion? Some of the aphantasics have an unconscious mind’s eye, but some really don’t.

PICTURE THIS Try imagining these scenes, designed to exercise different aspects of mental imagery, including colour and movement. How clear are the mental images?

The silhouette of the sun rising above the horizon Clouds gather. A storm blows up, with flashes of lightning The sky brightens and a rainbow appears Find out how you score and take a more detailed test of your mind’s eye at bit.ly/blindmind

It was those who appeared to have a mind’s eye without realising it that Pearson wanted to coach. So next he asked them to try visualising either the green or red striped pattern for a few seconds every day for five days. Back in the lab, he had them repeat the process, and this time he asked them to subjectively rate the strength of the image. Immediately afterwards, he simultaneously flashed the red pattern in one eye and the green in the other as before, and measured whether people had a perception bias. He was now armed with both a subjective and an objective rating of the minds’ eyes. In some cases he found the objective rating remained constant but the subjective rating improved, suggesting that the training had helped people begin to access a previously subconscious mind’s eye (Frontiers in Psychology, vol 3, p 224). In the spirit of investigation, I had to give it a go myself. When I did, a shapeless light flashed into my mind. It was the first time in my life that I’ve seen anything approaching a picture in my head. But I don’t think I’ll be continuing with the training. I’ve learned that I see the world in a unique way and I don’t want to give that up. ■ Dustin Grinnell is a writer in Los Angeles

Eye test solution: Only C is a rotated version of A.

It’s a rare mind that works exclusively in concepts not images

23 April 2016 | NewScientist | 37

Genes of the undead Our bodies contain a surprising amount of DNA from extinct human species. Colin Barras finds out what it’s doing to us NTIL about five years ago, one feature united the ancient human species that once walked the Earth: all were well and truly extinct. The Denisovans vanished from Eurasia around 50,000 years ago and the Neanderthals some 10,000 years later, leaving only Homo sapiens. Others went the same way much earlier, leaving just a few fossils – if that – to tell their story. But we now know these species are not entirely gone. Traces of them are buried within my cells and yours. By having sex with our direct ancestors, ancient human species made sure they left a genetic legacy that survives to this day, one with a greater significance than previously suspected. People of non-African descent inherit between 2 and 4 per cent of their DNA from Neanderthals; indigenous Melanesians get 3 to 4 per cent of theirs from Denisovans; and some hunter-gatherer groups in central Africa get a small proportion from species we haven’t even identified yet – we just know they existed. Crucially, recent studies have revealed that if you combine all the ancient DNA in living humans, you could recover a sizeable chunk of the original genomes. A study published this year suggests about 10 per cent of the Denisovan genome is still “alive”, mainly in people from Papua New Guinea. It also suggests that about 40 per cent of the Neanderthal genome can be put together from the bits living people carry. Joshua Akey of the University of Washington in Seattle thinks that figure may creep up with more research. The last few years of genetic decoding have revealed the surprising ways in which we express this legacy. It is partly responsible for the physical variation in modern humans – red hair and freckles have links with Neanderthal DNA, for instance – and it affects our health (see “Your inner extinct human”, page 40). And hidden in all this is a far bigger story: genes from our extinct cousins helped us 38 | NewScientist | 23 April 2016

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conquer the planet. Without them, our ancestors may not have coped with unfamiliar diseases, thrived in the thin air of the high Tibetan plateau, or withstood the chilly winds of the Arctic. These findings are testament to how much we owe humanity’s hybrids. And yet we know very little about who they were and how they coexisted with our ancestors. According to the latest estimates, our species mingled with other humans at least half a dozen times (see map, below). On each occasion, it’s likely that groups mixed and mated repeatedly over a number of generations, says Akey, producing many hybrid children. It might be significant that there is very little Neanderthal and Denisovan DNA on our X chromosome. This could be explained if matings were largely one-way, with male Neanderthals and Denisovans mating with female H. sapiens, who then raised the hybrid children in H. sapiens societies. Alternatively, the X chromosome’s lack of ancient DNA might be because hybrids suffered fertility issues: genes responsible for reduced male fertility are often found on the X chromosome. Or both explanations could be true. “[They] are not mutually exclusive,” says Sriram Sankararaman at the University of California in Los Angeles. Infertility might not have been purely down to genetics, of course. Did the hybrids struggle to fit in socially because of their appearance? An astonishing 40,000-year-old human male jaw found in Romania could offer clues. Last year, it was found to have 9 per cent Neanderthal DNA – much more than the 2 to 4 per cent that most living non-Africans have. Geneticists say the jaw’s owner must have been separated by a mere handful of

generations from a Neanderthal-human hybrid. The hybrid may even have been the man’s great-great grandparent. Erik Trinkaus at Washington University in St Louis, Missouri, had suspected the jaw’s hybrid roots. He and his colleagues had noticed its curious mix of human and Neanderthal traits: its rear molars, for instance, were strikingly large compared with modern human teeth. But features that are obvious to an anatomist wouldn’t have looked strange when the individual was alive, he says. Hybrids probably looked no different to anyone else, and may well have been treated exactly the same. This is perhaps not surprising, given emerging evidence that hybrids were a feature of human societies from the very beginning. A recent study of some hunter-gatherer tribes in Africa hints that mating between early H. sapiens and other ancient humans on the continent – the African equivalents of Neanderthals and Denisovans – was commonplace. This might even have given our ancestors some of the traits that allowed them to withstand the dramatic swings in the region’s environment during the Pleistocene. Statistical analysis of the hunter-gatherer genomes suggests this interbreeding ended only about 9000 years ago. That fits nicely with 12,000-year-old skulls discovered in Nigeria that have a mix of archaic and modern features, says Sarah Tishkoff at the University of Pennsylvania. Those skulls aside, though, we have no fossils of the species that lived alongside H. sapiens for nearly 200,000 years. African fossils have so far tended to be much older. Until we find younger ones, these mysterious humans can’t be given formal names – even though they might have played a pivotal role in the survival of our species.

HOMO PROMISCUOUS Our ancestors mated with other extinct human species on several occasions. Each time, two groups would have intermingled for generations, producing a number of hybrid offspring whose genetic traces live on in us. Ancient genomes are also yielding insights into our earliest migrations. In particular, a Neanderthal toe bone found in Siberia shows that Homo sapiens and Neanderthals interbred 100,000 years ago – 40,000 years before H. sapiens was thought to have left Africa. Some early explorer must have ventured out before the main migration. Perhaps one or more small groups went exploring, and met their long-lost cousins in western Asia.

Homo sapiens and Neanderthals 40,000 years ago ~60,000 ya ~60,000 ya