Law human: January 2015

Saturday, January 31, 2015

Zoologger: Judo spider finds armoured foe's Achilles heel

Video: Judo spider tackles armoured foe

Zoologger is our weekly column highlighting extraordinary animals – and occasionally other organisms – from around the world

Species: Loxosceles gaucho
Habitat: Human-made or disturbed natural environments in Brazil and Tunisia

In a fight between an armoured soldier and an unarmed opponent, who would win? When it comes to the recluse spider the answer might surprise you. Using its wits and speed, it can kill and eat one of its toughest prey: another arachnid, the armoured harvestman.

Harvestmen have a hard exoskeleton that protects them against several spiders, which are their main predators alongside birds and amphibians. Rodrigo Willemart from University of São Paulo, Brazil, and his colleagues found that even large predator spiders have difficulty piercing this armour.

For the attacker to have a half-decent chance, it needs to pin its prey between its fangs. "But this rarely happens, and usually both fangs slide on the surface of the harvestman's body," says Willemart.

Spiders have been seen attacking and eating harvestmen in the wild, but there are so few observations that harvestmen are generally left off lists of their frequent meals.

Dressed like Batman

"Harvestmen are somehow successful in avoiding predation from spiders, and it is well known many harvestman species exhibit several lines of defence," says Glauco Machado, also from University of São Paulo.

Those defences range from feigning death, which puts off most predators that feed on live prey, to releasing chemical irritants to repel attackers.

But Willemart and his colleagues found that armoured harvestmen seldom go for the chemical option, presumably because these compounds are costly to make. Instead, they rely on their exoskeleton for protection. But this backfires when recluse spiders exploit flaws in the armour's design.

Machado likens it to a Batman suit. When Batman asked for a more flexible suit, his business manager, Mr Fox, told him that more movement would imply more exposure to weapons such as knives, he says. "Of course, this lesson is relevant not only for the prey, but also for the predators," says Machado.

Willemart and his team found carcasses of harvestmen in the webs of recluse spiders in Brazil. These successful hunters were then brought to the lab, where 31 out of 38 spiders found a way to kill and then eat the harvestmen offered. So how do they do it?

Judo manoeuvre

The recluse spider carefully approaches and repeatedly feels out the harvestman with its own legs, looking for weak areas. The recluse spider can outrun any escape attempt, and may then do what Willemart likens to a judo move, pinning the harvestman's back to the ground. Finally, it delivers the death blow: a series of poisonous bites in the exact areas not shielded by armour.

"Recluse spiders are exceptional in that they do not try to pierce through the armour. They simply avoid it and bite the soft parts of the harvestman," says Willemart.

Although we now know how recluse spiders prey on harvestmen, much remains to be discovered.

"Do they use this strategy for all arthropod prey?" asks Eileen Hebets at the University of Nebraska, Lincoln. "Is this targeted biting behaviour learned? Is it innate?"

If this is a learned behaviour, Hebets suggests researchers can explore how they learn it in the first place and remember it for future use. She says spiders are great subjects for lab study of mechanisms of complex behaviours in animals, as they are easy to catch and exhibit complex behaviour themselves.

Journal reference: Animal Behaviour, DOI: 10.1016/j.anbehav.2014.12.025

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Data archaeology helps builders avoid buried treasure

IN 2010, when builders were excavating the site of the former World Trade Center in New York, they stumbled across something rather unusual: a large wooden boat, later dated to the 1700s.

Hitting archaeological remains is a familiar problem for builders, because the land they are excavating has often been in use for hundreds, if not thousands, of years.

Democrata, a UK data analytics start-up, wants to help companies guess what's in the ground before they start digging. Using predictive algorithms, their new program maps where artefacts might still be found in England and Wales, in order to help companies avoid the time and cost of excavation. "It's an expensive problem to have once you've started digging," says Geoff Roberts, CEO of Democrata.

Archaeological services can amount to between 1 and 3 per cent of contractors' total construction cost. "We wanted to bring data science in as an added tool, so humans involved in the process could use it to understand what would likely be found," says Roberts.

The Democrata team scoured documents from government departments such as the Forestry Commission, English Heritage and Land Registry to find out what the land was used for in the past, for example, and about known archaeological sites. This included "grey literature", the massive set of unpublished reports written by contractors every year.

With the aid of a supercomputer, they developed models that can pinpoint where treasures are likely to be hidden underground. For instance, land close to water, tin mines or sites of religious significance was ranked more highly than land elsewhere. Other factors like the local geology, animal and plant life also contributed to the score.

This week, Democrata will present the program to engineering companies and the government to hear their feedback.

Henry Chapman at the University of Birmingham, UK, says the tool may impede new discoveries in archaeology. "If you think about the number of archaeological fieldwork excavations that take place purely for trying to find out about the past, that's a very small amount compared to all of the excavations done before commercial development," he says.

This article appeared in print under the headline "How to avoid buried treasure when you dig"

Thursday, January 29, 2015

Ancient planets are almost as old as the universe

Video: Ancient planets are almost as old as the universe

The Old Ones were already ancient when the Earth was born. Five small planets orbit an 11.2 billion-year-old star, making them about 80 per cent as old as the universe itself. That means our galaxy started building rocky planets earlier than we thought.

"Now that we know that these planets can be twice as old as Earth, this opens the possibility for the existence of ancient life in the galaxy," says Tiago Campante at the University of Birmingham in the UK.

NASA's Kepler space telescope spotted the planets around an orange dwarf star called Kepler 444, which is 117 light years away and about 25 per cent smaller than the sun.

Orange dwarfs are considered good candidates for hosting alien life because they can stay stable for up to 30 billion years, compared to the sun's 10 billion years, the time it takes these stars to consume all their hydrogen. For context, the universe is currently 13.8 billion years old.

Metal light

Since, as far as we know, life begins by chance, older planets would have had more time to allow life to get going and evolve. But it was unclear whether planets around such an old star could be rocky – life would have a harder time on gassy planets without a solid surface.

The first stars to form in the universe were made of just hydrogen and helium, and forged heavier elements in their interior before exploding. The next generation of stars emerged from their debris, and incorporated those heavier elements into their cores and whatever planets they formed. This means that in general, older stars have fewer metals.

Until recently, planet-hunters assumed that stars needed metals to form planets, partly because the first planets they discovered all orbited metal-rich stars, and partly because planets themselves are made of heavier stuff than hydrogen and helium. But a 2012 survey of Kepler planets showed that low-metal stars could host relatively small planets.

"We knew beforehand that small planets could exist around stars of any metallicity, but it was not really well known if we could go down to Earth-sized planets," Campante says.

Kepler 444's planets are all smaller than Earth, ranging from 0.4 to 0.74 times Earth's radius. Kepler data suggests that planets tend to be rocky when they're smaller than 1.7 Earth radii, and gaseous when they're bigger, making the Kepler 444 worlds almost certainly rocky. But they orbit scorchingly close to the star: the furthest, Kepler-444f, orbits once every 9.7 days, and the closest, Kepler-444b, every 3.6 days. The length of their orbits are all multiples of each other, meaning they eclipse each other regularly and every so often line up all in a row.

Planets align

"You can imagine if you are standing on the surface of the outermost planet, at some points during the orbit you could look in the direction of the star and see all the other four planets aligned," Campante says. "It must be amazing."

To find out how old the star is, Campante and his colleagues used a technique called astroseismology to measure the age of the star very precisely. With the help of the Kepler telescope's entire four-year data set, the team watched Kepler 444's brightness change over time. These fluctuations reflect vibrations within the star, which tell you its mean density. Because a star converts hydrogen to helium in its core as it ages, changing its density, knowing a star's density tells you how old it is.

This technique gave Kepler 444 an age of 11.2 billion years, plus or minus 1 billion years. That makes it the oldest known system of terrestrial planets in the galaxy – when Earth formed, these planets were already older than our planet is today. (The previous record-holder, a red dwarf known as Kapteyn's star, hosts larger planets that are probably mini-Neptunes.)

"These planets mean it only took the universe a couple billion years to figure out how to build rocky planets, and they've been around for a really long time," says Travis Metcalfe at the Space Science Institute in Boulder, Colorado. While Kepler 444's planets are too hot for life, its age suggests there might be cooler, older worlds elsewhere. "If life needs a long time to develop or lots of places to try to develop, having rocky planets this early in the history of the galaxy means planets with advanced civilisations should be everywhere."

"These are all little bits of good news," says Andrew Howard at the University of Hawaii at Manoa. "There are still a lot of other hurdles life would have to overcome, but now we're seeing evidence that small planets are common, and here we have one from when the Milky Way was a kid and it was already forming probably rocky planets."

The next step is to figure out exactly what they're made of, he says. His team has been using the Keck telescope in Hawaii to try to get a handle on these planets' masses by measuring their gravitational tugs on the star. Knowing the planet's mass and radius gives its density, a clue to composition – but the masses are proving too small to measure.

"That's not surprising or concerning, it just confirms that these are really small planets," he says.

Journal reference: arxiv.org/abs/1501.06227

Sperm whale's emergency evacuation... of its bowels

(Image: Keri Wilk)

ENCOUNTERING a mighty sperm whale is a magical experience. But in this case, it was tempered somewhat by a rarely seen defence mechanism: emergency defecation.

Sperm whales are the largest toothed predators in the world, so what have they got to be scared of? Here it was pesky divers buzzing around them, taking photos.

Canadian photographer Keri Wilk was sailing off the island of Dominica in the Caribbean, hoping to film these gargantuan creatures, when he spotted one and jumped in for some close-ups. The whale approached Wilk and his three colleagues, pointed downwards, and began to evacuate its bowels. To make matters worse, it then started to churn up the water. "Like a bus-sized blender, it very quickly and effectively dispersed its faecal matter into a cloud," says Wilk.

(Image: Keri Wilk)

Defensive defecation has been recorded in pygmy and dwarf sperm whales, which, as their names suggest, are diminutive compared with their cousins. But this is perhaps less surprising, given that they have natural predators. Wilk is unaware of any other reports of sperm whales' emergency excretion.

Despite what you might think of being enveloped in what Wilk describes as a "poonado", he cherishes the moment. "I've experienced lots of interesting natural phenomenon underwater, all over the world, but this is near the top of the list," he says. "As long as you didn't take your mask off, you couldn't really smell anything. Taste is another matter..."

This article appeared in print under the headline "Watch out, it's a poonado!"

Laser flight path caught on camera for the first time

Video: Laser flight path caught on camera for the first time

Pew pew! Researchers have created the first video of a laser bouncing off a mirror.

Watching laser beams fly through the air makes for dramatic battles in sci-fi films, but they're not so easy to see in real life. In order to observe a laser, or any other light source, photons from it must directly hit your eyes. But since laser photons travel in a tightly-focused beam, all heading in the same direction, you can only see them when the laser hits something that reflects a portion of the light and produces a visible dot.

A tiny proportion of photons scatter off air molecules, but normally these are too faint to see. You can get around this by firing a laser through smoke, giving the photons more molecules to scatter off – but that's not the effect we see in the movies.

"The challenge was to have a movie of light moving directly in air," says Genevieve Gariepy of Heriot-Watt University in Edinburgh, UK. "We wanted to look at light without interacting with it, just looking at it passing by."

To make this work, she and her colleagues constructed a camera sensitive enough to pick up those few scattering photons. It is built from a 32 by 32 grid of detectors that log the time a photon arrives at them with incredible precision, equivalent to snapping around 20 billion frames a second.

Lighting the way

The team arranged the camera to film a side-on view of a green laser firing at an arrangement of mirrors. By firing 2 million pulses over a 10 minute period and subtracting background noise, they were able to build up enough air-scattered photons in the camera to track the laser's path as it bounced.

"What comes out is a frame by frame of the light moving through our system," says Gariepy. In their video, this position data is overlaid on a background photograph taken with a regular camera, and coloured green to match the laser's true colour.

The experiment started as a pure research challenge, but Gariepy thinks their camera could have practical applications. In another experiment, the team filmed a focused laser that ionised air molecules to produce a plasma. Gariepy says a similar setup could help people studying the properties of such plasmas by letting them watch the plasma evolve over time.

Precise timing data could also be used to measure the distance photons have travelled, an effect previously exploited to take pictures around corners. "It takes maybe an hour or so to acquire an image" around a corner, says Gariepy, but the ability to take multiple images rapidly could generate movies from around corners. "With our camera this can be done in seconds."

Journal reference: Nature Communications, DOI: 10.1038/ncomms7021

Wednesday, January 28, 2015

Ancient water cache may be pristine primordial soup

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Deep rocks have been cracked open and water isolated for billions of years released – the liquid may represent Darwin's “warm little pond” where life arose

IT IS the closest we have ever come to finding Earth's primordial soup. Ancient rocks deep underground contain water that has been locked away for billions of years. It may never have been touched by life.

In 2007, geochemist Barbara Sherwood Lollar at the University of Toronto in Canada and her team found treasure in a copper mine. Water gushing out of cracks in the rock, caused by mining, turned out to be over a billion years old. Now the group has made a similar find in a second mine, suggesting ancient rocks could be riddled with such time capsules, right back to the early days of life on Earth.

Sherwood Lollar's team is now scouring the water for ancient forms of life, perhaps unknown to science. So far it seems it holds no life, but that is just as exciting because it means the water they found may be identical to that in which life began.

If that's the case, it opens up an extraordinary opportunity to understand how life got started on Earth, and where (see "Beginner's guide to the origin of life"). The find could also offer insights into how life may survive on other planets.

Sherwood Lollar first got a whiff of the hidden water over a decade ago, deep inside the Kidd Creek Mine in Timmins, Ontario, Canada. In a corridor more than 2 kilometres beneath the surface, she caught a whiff of gas from a fracture in the rock. Water dripped from the hole. Subsequent analyses revealed it to be between 1.1 and 2.7 billion years old (Nature, doi.org/tgw). The smell came from the sulphurous gases mixed in with the water, which also holds methane and hydrogen.

Crucially, as far as the team could tell, the water contained no trace of life. "It speaks to this question of whether we can find an exotic small part of this planet that has not been touched by life," says Sherwood Lollar. "These fractures may have been isolated long enough that they retain chemistry that reflects the same kind of processes that were taking place before there was life on Earth. At that time, presumably the whole planet would have looked something like this."

The discovery could have been a one-off, so the team has been looking for other places where ancient water exists in deep rocks. Last month at the Goldschmidt conference in Sacramento, California, team member Chelsea Sutcliffe presented their results from two mines in the Sudbury basin, also in Ontario.

Like Timmins, the mines are dug into rock that is billions of years old. Sutcliffe collected water from 1.3 and 1.7 kilometres down, and so far it looks very similar to the Timmins water. The chemicals in the water are similar, and isotope ratios suggest it is similarly old. The team are now running further analyses: the noble gases in the water samples will provide a fairly precise age.

"If they are seeing the same thing at Sudbury, that's pretty powerful," says Tullis Onstott of Princeton University. This water is "an abiotic fringe zone – a place where life could exist but doesn't yet", he says. "This is a zone that's been trapped for billions of years, providing a geological experiment on the genesis of life."

At most, the Timmins and Sudbury water is 2.7 billion years old – the age of the rock it is trapped inside. That's about a billion years after life got started, so the researchers are not suggesting they have bottled the actual primordial soup in which life began. But the chemistry they are seeing corresponds to water that could have given rise to life.

"Geochemically, it's the kind of site that has been invoked for the origins of life on our planet," says Onstott. "Yet here we see it isolated from the present-day DNA world."

There are two leading theories for where life got started on Earth. Perhaps the most famous is Darwin's "warm little pond" – a soup of organic chemicals bathed in sunlight. The other, which has gained popularity in recent years, is that deep-sea vents at the bottom of the ocean acted as a cradle for life, offering both heat and nutrition via fluids pumped up through Earth's crust.

That's where the ancient water from the Ontario mines comes in. The rocks they are held in were formed by hydrothermal vent systems at the bottom of the ocean, billions of years ago.

"I would say this is as close as we have come to bottling the warm little pond, in a warm little fracture," says Sherwood Lollar. Onstott agrees: "They are literally like Darwin's warm little pond without the light."

Having bottled Earth's primordial soup, the researchers are now probing it to see what they can learn. It may be that chemical reactions deep underground have given rise to some of the very earliest stages in the formation of life, like the generation of amino acids, or the building blocks of DNA.

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E. O. Wilson: Religious faith is dragging us down

Your new book, The Meaning of Human Existence, addresses a huge question. What inspired you to tackle it?
I think it's time to be audacious. The central questions of religion and philosophy are three in number: where do we come from, what are we and where are we going? Usually these are just the beginnings of long discussions, but that's no longer the case. We now have a pretty good picture of how humanity arose in Africa, what intermediate forms existed, the rate at which these forms evolved and the circumstances in which they evolved.

So I can say, right now, that of those three great questions, we have most of the answer for where we come from. And in this book I take up the question: what are we? We're starting to close in on that one. We need to know where we came from and what we are to ...

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Tuesday, January 27, 2015

Death rate drops when top heart surgeons are away

IF YOU have a serious heart problem just when the top surgeons are away at a medical conference, take heart. Their absence could increase your chances of survival.

Harvard Medical School healthcare policy researcher Anupam Jena and colleagues examined tens of thousands of people who were admitted to hospital with a heart attack, heart failure or cardiac arrest between 2002 and 2011.

Among the most severe cases of cardiac arrest, 70 per cent of those admitted when no cardiology conference was taking place died within 30 days. But among those admitted when expert cardiologists were away at meetings, the corresponding death rate was 60 per cent (JAMA Internal Medicine, doi.org/xzw).

The results suggest that for the most seriously ill heart patients, the risks of emergency interventions such as artery widening may outweigh the benefits, Jena says. The findings should not lead to a change in doctors' practice without further research, but should be seen more as a warning signal that very ill people sometimes receive too many interventions.

"All patients are not the same: the risk that they can tolerate is very different," he says. "In some cases that might mean we have to treat patients more conservatively."

This article appeared in print under the headline "Heart surgeons away? No sweat"

Tape of life may not always be random

Evolution may have fewer options for adapting to new challenges than you'd think. When terrestrial mammals returned to the ocean to become whales, walruses and manatees, the three lineages sometimes made use of strikingly similar genetic changes.

Evolutionary biologists have long debated whether rewinding the tape of life and replaying it would give similar results, or whether outcomes depend largely on chance events that push the course of evolution onto radically different tracks.

The two alternatives yield very different views of the history of life on Earth, with some prominent biologists, such as Simon Conway Morris, arguing that human-like, intelligent beings are inevitable products of evolution.

Others, such as palaeontologist Stephen Jay Gould, who popularised the tape of life metaphor, argue that if it were possible to turn back the clock, the history of life would not repeat itself. The world would be unfamiliar, and most likely lack humans.

To test the reproducibility of evolution at the genetic level, an international team took advantage of a natural experiment. Three different groups of terrestrial mammals have at some point in their evolution re-colonised the ocean, giving rise to what we now know as whales, walruses and manatees. Comparing the genetic changes in the three lineages, the researchers reasoned, should reveal whether evolution followed similar or very different paths in each case.

Random idea

They sequenced the genomes of walrus, manatee and two whales – killer whales and bottlenose dolphins. The comparisons showed that many genes changed independently in each lineage, suggesting that randomness did indeed play an important role in their evolution.

But for 15 genes, natural selection led to exactly the same genetic changes occurring in all three lineages. This suggests that for some of the challenges of life in the sea, evolution repeatedly arrived at the same solution – that is, replaying the tape does indeed give much the same result again and again. This is a high-resolution replay of the tape, looking at what would happen to individual lineages, rather than what overall diversity would eventually result, which is what Gould looked at.

The team has not yet shown directly that any of these convergent genetic changes is actually adaptive, though some they found – affecting, for example, the structure of ear bones or metabolism related to deep diving – could plausibly be so.

However, this result may say less about the predictable creativity of evolution than about a paucity of viable options. When the team performed a similar analysis of the genomes of dog, elephant and cow – related mammals that remained on land – they also found a comparable amount of convergence in their mutations, even though those animals share few similarities of lifestyle.

Lack of options

This may imply that the vast majority of mutations are lethal, so that evolution stumbles on the same few viable ones over and over again. "We think it's because there's only so much you can change and still be functional," says Kim Worley, a genome biologist at Baylor College of Medicine in Houston, Texas.

"If you replayed the tape, you'd probably see the same changes again amongst the marine mammals, but if you took a walrus and a camel, you'd still see the same changes, because of these constraints," says Andrew Foote , an evolutionary biologist at the University of Copenhagen.

But David Wake, an evolutionary biologist at the University of California at Berkeley, cautions that the study was essentially a genome-wide fishing expedition to look for interesting patterns. Much more detailed follow-up work will be needed to show whether the team's hypothesis holds up.

"I find it intriguing, but I think the evidentiary basis for it is still pretty weak," says Wake. "But we're just starting out."

Journal reference: Nature Genetics, DOI: 10.1038/ng.3198

This baby coral will grow up to patch ailing reefs

(Image: Tim Calver/Tim Calver Photography)

A SMALL school of grunts is unfazed by the photographer as they swim over this tiny coral oasis off Florida's coast. But this is no ordinary reef: it has been made by biologists trying to farm corals to transplant onto damaged reefs. Many species are in need – staghorn coral (Acropora cervicornis), the kind pictured, has experienced a 98 per cent decline over the past 30 years, leaving it scattered and facing local extinction.

"The images show two approaches to the same problem: getting coral fragments to grow into healthy coral pieces," says Tim Calver, the wildlife photographer who shot these images off the coast of Key Largo, at the very top of the Florida Keys. The coral is clipped from healthy stock then glued to cement blocks or tied to vertical strings, where it is elevated into the current, its nutrient source. It is left to grow for a few months until it's big enough to be transplanted.

This nursery is run by the Coral Restoration Foundation, whose president, Ken Nedimyer, can be seen below inspecting the growth of baby corals. The organisation has replanted thousands of colonies – most of which have survived. "To be in the water and to know it's a success story is just fantastic," says Calver.

This article appeared in print under the headline "School's out on the reef"

Ancestry of first Americans revealed by a boy's genome

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The genes of a boy who died 12,600 years ago show that all indigenous people in the Americas seem to be descended from the same group of ancestors

WE MAY never know who the Anzick child was. Why he died, just 3 years old, in the foothills of the American Rockies; why he was buried, 12,600 years ago, beneath a huge cache of sharpened flints; or why his kin left him with a bone tool that had been passed down the generations for 150 years.

One thing, however, is certain: his afterlife is anything but ordinary. This week, geneticists announced that the boy is the earliest ancient American to have his entire genome sequenced. Incredibly, he turns out to be a direct ancestor of most tribes in Central and South America – and probably the US too – as well as a very close cousin of Canadian tribes.

"It's crazy," says Eske Willerslev of the University of Copenhagen in Denmark, who led the genomic analysis. "Finding someone who is directly ancestral to the entire population of a continent – that just does not happen. I don't think it would ever happen in Europe, or in Siberia. There are very few places where this could happen."

"The reason," he says, "must be that this skeleton is really close to the source – really close to the 'Adam'. I think that is the only explanation."

The find offers the first genetic evidence for what Native Americans have claimed all along: that they are directly descended from the first Americans. It also confirms that those first Americans can be traced back at least 24,000 years, to a group of early Asians and a group of Europeans who mated near Lake Baikal in what is now Siberia. And it dispels a controversial theory that the Americas were first populated by west Europeans who somehow crossed the Atlantic Ocean.

The boy was discovered in Montana in 1968, when diggers working on land owned by the Anzick family accidentally ploughed into a huge cache of stone tools. The flints were typical of the Clovis period, a short archaeological period in North America lasting from 13,000 to 12,500 years ago. Beneath them lay a handful of bone artefacts and a skeleton.

Clovis artefacts are scattered all over the western US. Archaeologists largely believe that the first Americans arrived by a land bridge from Asia about 15,000 years ago, and some went on to develop Clovis tools (see "A history of the first Americans in 9½ sites").

Willerslev and his colleagues were able to extract enough viable DNA from the boy's badly preserved bones to sequence his entire genome.

They then compared this with DNA samples from 143 modern non-African populations, including 52 South American, central American and Canadian tribes.

The comparison revealed a map of ancestry. The Anzick child is most closely related to modern tribes in Central and South America, and is equally close to all of them – suggesting his family were common ancestors. To the north, Canadian tribes were very close cousins. DNA comparisons with Siberians, Asians and Europeans show that the further west populations are from Alaska, the less related they are to the boy.

Fully sequenced genomes remain rare, so the bulk of the analysis was done by looking at genetic markers known as single nucleotide polymorphisms or SNPs. To confirm the pattern, Willerslev and his team sequenced full genomes from three contemporary Mayan and Karitiana individuals in Central and South America.

The findings offer genetic confirmation that the first Americans crossed the land bridge that once stretched from Siberia to Alaska across the Bering Strait.

"The Clovis population seems to be more closely related to South Americans than to native North Americans," says David Reich of Harvard Medical School in Boston. "That's telling you that the Clovis sample seems to have occurred after the initial split of the lineages that gave rise to native South Americans and native North Americans."

Unfortunately, long-standing tensions between US tribes and scientists mean there is no significant genetic data available from these peoples (see Leader, "An ancient genome alone can't heal long-standing rifts"). Having that data, says Reich, could help determine which groups lie on either side of the North and South American family tree.

In November, Willerslev published the genome of another ancient boy, the 24,000-year-old Mal'ta boy, from the shores of Russia's Lake Baikal. The boy's DNA showed he descended from a mating between early Asians and proto-Europeans, and that he is related to modern South Americans. Like modern South American DNA, the Anzick DNA is a mix of Mal'ta and other Asian DNA, pointing to a "source" population for the first Americans, probably in far eastern Siberia (see map).

But how many first Americans were there, and did they come all at once or as a slow trickle? "The most likely scenario is that a single migration of people into the heartland of North America around 15,000 years ago gave rise to the Clovis and their descendants, which includes modern Native Americans," says Mike Waters of Texas A&M University in College Station, a co-author with Willerslev on the latest study. "This is supported by the archaeological and genetic evidence."

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Polar bear penis bone may be weakened by pollution

First climate change, now penile fracture – polar bears have got it pretty rough. Chemical pollutants may be reducing the density of the bears' penis bones, putting them at risk of breaking this most intimate part of their anatomy.

Various mammals, though not humans, have a penis bone, also known as penile bone or baculum. Its exact function is unclear: it could be just a by-product of evolution, or it may help support the penis or stimulate the female during mating.

Christian Sonne at Aarhus University, Denmark, and colleagues had previously shown that polar bears with high levels of pollutants called organohalogens in their bodies had both smaller testes and a smaller penis bone.

Sonne and his team have now shown that a particular class of organohalogens, the polychlorinated biphenyls (PCBs), is associated with a less dense baculum. This could prevent successful mating, the team suggest.

PCBs were used industrially for several decades from the late 1920s onwards. They had hundreds of applications, including in production of paints and rubber products. Then evidence emerged that they can harm health and cause cancer, and were banned by a UN treaty signed in 2001. But they are slow to break down, so can accumulate in the environment.

Polar deposits

The Arctic has particularly high concentrations of pollutants like PCBs, says Margaret James at the University of Florida in Gainesville. "These chemicals enter the atmosphere at lower latitudes where they were used, and are then deposited down from the cold polar air, so Arctic animals are more highly exposed than animals in more temperate or equatorial regions."

To see what effect high concentrations of PCBs might be having on the bears' mating, Sonne's team collaborated with researchers in Canada to examine baculum specimens from 279 polar bears from north-east Greenland and Canada, all born between 1990 and 2000.

They studied this bone because it's easy to come by. "It's the kind of bone that's taken by local trophy hunters and subsistence hunters. It's an actual sign that you have hunted and shot a bear," says Sonne.

They used a hospital X-ray technique to calculate the density of calcium in each bone. Comparing their figures against data on locally recorded levels of a range of harmful pollutants, they found a link between high PCB levels and low baculum density, although James notes that the analysis was not strong enough statistically to prove that PCBs are the cause of lower bone densities.

Even though the function of the polar bear's penile bone is unknown, Sonne believes that a weaker baculum is likely to be problematic during mating. "If it breaks, you probably won't have a bear which can copulate."

Twin stresses

Sonne believes that, especially considering the stresses on polar bears from climate change, chemical pollutants are likely to be having an effect on populations too – but it's difficult to say how much of one. "We don't know because it's so hard and expensive to go and do satellite tracking and repeated measures of the same bears," says Sonne.

Andrew Derocher at the University of Alberta in Edmonton, Canada, agrees that the interaction between climate change and pollution is a concern. Climate change increases break-up of ice and so reduces the bear's ability to forage. "Skinny bears have higher levels of circulating pollutants, so the concern is that a bear that is nutritionally stressed may become more vulnerable to the effects of pollution at the same time," says Derocher.

Sonne and his team now want to investigate whether food stress and pollutants have been driving evolutionary change in the bears. He believes that the chemicals are likely to have killed many bears over recent decades, so may have shaped changes in the species' genetic make-up.

Journal reference: Environmental Research, DOI: 10.1016/j.envres.2014.12.026

Monday, January 26, 2015

Surreal X-ray movie reveals how a fly beats its wings

Video: Surreal X-ray movie reveals how a fly beats its wings

This surreal view inside the body of a blowfly is reminiscent of the imagery in the film Alien. Graham Taylor at the University of Oxford and colleagues used X-rays produced by a particle accelerator at the Paul Scherrer Institute in Switzerland to peer at the muscles of a live blowfly, in order to study how it beats its wings.

This video, which focuses on the fly's thorax, highlights the muscles that help it fly. The large muscles shown in red, orange and yellow provide the power that keeps the fly aloft, while the much smaller muscles shown in green, blue and cyan are used for steering. Each muscle contracts and relaxes in a single direction, but their collective motion creates a complex beat pattern that moves the fly's wings in three dimensions.

The mechanism may inspire engineers designing tiny mechanical devices. While conventional designs use clockwork, a collection of actuators that each bend and flex in only one direction – just like the fly's muscles – could achieve the same result more efficiently.

Journal reference: PLoS Biology, DOI: 10.1371/journal.pbio.1001823

Finding ET – we're gonna need a bigger dish

The hunt for alien civilisations may need a rethink. A new paper argues that the signals we're listening for might not be the ones ET would choose.

Historically, SETI – the search for extraterrestrial intelligence – involves scanning the sky for radio signals that another civilization is deliberately sending. The simplest would be a constant blast in all directions, but in a narrow range of frequencies, similar to early radio broadcasts – like a constant hum that would tell a listener it is artificial. From light years away, we would not be able to get any other information – all we would be able to tell from Earth is that a signal was there and where it was coming from, not what it says.

But David Messerschmitt at the University of California, Berkeley points out that such a continuous signal would take a tremendous amount of energy. Assuming aliens have utility bills, he says, they would use a different strategy.

They would also probably want to say something more than "we are here" by adding information to the signal. All attempts to send messages to ET from Earth have contained information, sometimes a lot of it. One of the most famous, the Arecibo message sent in 1974, which encoded details about humans, DNA, the solar system and more.

"All our discussions about transmitting ourselves include information, and how to encode it such that ET can understand our message and what to include in the message," Messerschmitt says.

To do this most efficiently, instead of a constant, narrow-band signal, Messerschmitt argues that ET would beep out short bursts in a wider range of frequencies – a broadband signal. This would take less energy to transmit, and could encode information.

Current SETI searches are not designed to pick up information in that kind of signal, notes Seth Shostak, director of the Center for SETI Research at the SETI Institute in California.

"The problem is that… encoding a message; means that any signal would vary quickly," Shostak says. "To see such variations – to get the information in the signal – requires having enough sensitivity to see changes in a 10th or 100th of a millionth of a second. That requires antennas with collecting areas maybe 10,000 times larger than necessary to detect a steady signal." No such antennas currently exist that would pick up the variations more than a few light years away.

But Messerschmitt thinks there's a workaround. Existing software, such as that used for the SETI@Home project, which processes millions of signals using idle home computers, could be adapted to extract information from a signal. SETI@Home looks at many channels at once seeking narrowband signals, but it could be programmed to look for broadband ones instead.

He doesn't think this means the current approach to SETI should be halted, but rather expanded to also look for this alternative form of signal.

"I would not advocate putting all our eggs in one basket," says Messerschmitt. "We really don't know what ET is up to."

Journal reference: Acta Astronautica, DOI: 10.1016/j.actaastro.2014.11.007

Sunday, January 25, 2015

Shapely photons break rules to fly slower than light

Anyone struggling with a New Year's fitness regime knows that you move slower when you're out of shape. Now it seems the same is true even for light, which up until now physicists had thought travelled at a constant speed.

It's well known that light travels more slowly when it passes through different materials. This phenomenon, known as refraction, creates optical illusions like a seemingly broken drinking straw sticking out of a glass of water. But the speed of light in a vacuum, a little under 300,000,000 metres per second, is an unwavering constant that underpins much of modern physics, including Albert Einstein's theory of relativity. It's so important that physicists give it a single letter: c.

Now, Miles Padgett at the University of Glasgow, UK, and his colleagues have shown this isn't quite right. Light travelling in a plane wave – the traditional up and down squiggle you learn about in school – always travels at c, but light with a more complex wave structure travels slightly slower, by about a thousandth of a per cent.

Light on time?

The team revealed this oddity by studying two kinds of shaped light: a Bessel beam, which looks like concentric rings of light, and a Gaussian beam, which spreads out as it travels. They used an ultraviolet laser to produce pairs of photons and passed one photon through a filter to shape it into either a Bessel or Gaussian beam. Both photons travelled one metre before hitting a detector, so they should have arrived at the same time, but the shaped photon was slightly delayed.

Why does this happen? One way of thinking about it is that some of the light in a structured beam is moving in the "wrong" direction – sideways rather than forwards. This isn't a strictly accurate picture of the energy distribution within the beam, warns Padgett, but it is a way to imagine what might be going on. "Personally I think that's a useful concept, though the scientific rigour police might not welcome it."

Don't rip up your physics textbook just yet though – the implications are likely to be minor, only affecting certain short-range experiments that rely on very precise time-of-flight measurements, for example. "We're not challenging Einstein," says Padgett.

Hints of this effect have been seen in other experiments, but no one had quite pinned it down before, says Ulf Leonhardt at the Weizmann Institute of Science in Rehovot, Israel. "[This] is really the first clean and clear experiment where the speed of photons in structured light beams is directly measured," he says. Now that physicists understand it, they might be able to exploit it. "I do not foresee immediate applications in the short run, but important fundamental physics always has implications and applications in the long run."

Correction: The original version of this article reported the speed of light in a vacuum as 300,000 metres per second.

Journal reference: Science, DOI: 10.1126/science.aaa3035

A day in the life of a patent examiner

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The interview was produced by New Scientist in conjunction with the European Patent Office, which paid for it to be produced.

Innovation often starts with a "light bulb moment". But after that it's up to a team of sharp-eyed patent examiners to figure out whether a new invention deserves to be protected with a patent. Dai George asks patent examiner Laura Smith-Hewitt what it's like to work at the European Patent Office (EPO).

What does a patent examiner at the EPO do?
At the EPO, our main job is to grant patents to inventors. We offer a uniform application procedure so that inventors can seek protection for their innovation in up to 40 countries across Europe, all through a single application in English, German or French.

Patent examiners carry out the fundamental work of the EPO, in accordance with the European Patent Convention. Every patent examiner specialises in a particular field, based on their science background. In my time so far at the EPO I've worked in several areas: I started out examining general-use laboratory technology, such as that used in medical diagnostics and forensics, and more recently I've specialised in the electrical analysis of fluids, particularly glucose sensors. For every application we receive, we search for similar inventions that have come before, looking for what we call "prior art", and examine the claims of the new invention. We can only grant a patent if the technology demonstrates an "inventive step", which means that the inventor has made reasoned and objective progress on what came before by solving a technical problem.

What kinds of patent applications are sent to you?
I see all sorts of different applications. We have applications from individuals but they're relatively rare. Many applications come from the global players in industry – the company that files the most patents to us is Samsung, for example. But many big companies also licence-in or buy new technologies developed by small groups of research scientists.

We also receive a lot of applications from university departments. The EPO functions as a crucial link between academic science and the technology market. It is becoming increasingly important for universities to protect their intellectual property, so that they can spin off and sell the fruits of their research to technology companies.

Does a patent examiner need to have a science or engineering degree?
For any patent that I see, I need to be able to understand the technology behind it. When someone is applying to patent a diagnostic device, I have to know how that device works. I have a master's degree in chemical engineering, and these skills help me to understand the claims and description for the technology quickly, along with any scientific drawings that the applicant provides.

So yes, patent examiners need a science or engineering degree that is relevant for the technical field they want to work in.

What other skills and attributes do you need to be a good patent examiner?
Examining any application takes a sharp eye for detail and an analytical mind. You need to be able to judge carefully whether an application meets the requirements of the law. If a patent can't be granted for an invention, you must provide the applicant with reasoned objections in a clear and concise way, so that they have the opportunity to try to overcome them. Making such judgements relies on being thorough in your research and knowing the applicable patent law.

When someone files a patent, I have to find the prior art, and that requires me to look through a lot of patents and academic or technical literature using our IT tools. Every day I retrieve the most relevant documents from a huge range of databases, and I need to understand those documents quickly when I read them. It takes a great deal of persistence.

You should be ready for quite a steep learning curve. When I first came to the EPO, I knew nothing about the law at all, so I had to learn the European Patent Convention from scratch. The legal and technical training is comprehensive and lasts for the first two years of your career at the EPO.

There are three official languages of the EPO – English, French and German. You really need to know them all to work here. In some cases, if you can demonstrate strong skills in only two languages – say, if you're a UK citizen with English as a mother tongue, but you have good knowledge of French – it's possible to be employed on a three-year contract, which becomes permanent once you have acquired sufficient skills in the third language.

The EPO has offices in Germany and the Netherlands. Are there any perks to working abroad?
What's nice is that you're not judged on where you come from. Once you're in, you're judged purely on what you do – there's no hierarchy based on which university or school you attended. I came here at the same time as a batch of people who were in the same boat as me. Nobody knew anyone else's background, and it's a bit like starting a new university course in that respect, though of course it's very much a work environment. You all study for the same courses on law and how to use advanced retrieval tools to search for patents, and those intense weeks that you spend together contribute to lasting friendships. I'm still going to lunch with the people I met on my first day here. You bond together, and then it's very interesting to find out about other people's backgrounds and culture.

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Weird cosmic echoes may offer new glimpse of big bang

HEAR that? Echoes bouncing around the universe might be carrying messages from shortly after the big bang.

The earliest light in the universe is more than 13 billion years old, its photons dating back to an era when plasma generated in the big bang cooled enough to let light through. These photons carry information about the state of the early universe, but have been growing ever fainter. Now they form the cosmic microwave background, a low-level sea of radiation permeating the universe.

Eduardo Martín-Martínez of the University of Waterloo in Ontario, Canada, and his colleagues think they have found another, better-preserved source of clues about the very early universe. They calculated that events which produce photons – such as an atom releasing energy – also create certain echoes in the electromagnetic field, the very field which forms the basis of light.

To test how these could carry information, the team imagined someone in the early universe sending a message into the distant future by creating a series of echoes and using them to encode a string of 0s and 1s. These echoes travel slower than light but do not fade, meaning they can carry more information than photons over large distances (arxiv.org/abs/1501.01650).

"We prove how an intelligent entity can use this phenomenon to transmit much more information than just plainly sending a radio signal," says Martín-Martínez. Of course, it's pretty unlikely that intelligent aliens from the distant past are trying to signal us in this way, but the principle means it could be worthwhile for cosmologists to look out for these echoes.

"Information about background signals from the early universe will also be propagated through this echo," he says. The challenge is to figure out precisely what form the echoes will take and how to build receivers that can pick them up.

Avi Loeb of Harvard University says it's an interesting idea, but still quite theoretical. "The authors need to give specific examples of observables that would show their effect," he says.

This article appeared in print under the headline "Ancient echoes speak to us from the big bang"

Rights versus bites: The great shark culling debate

Great whites may be behind most attacks around Perth (Image: David Jenkins/Corbis)

Sharks have killed seven people off Western Australia since 2010. Can culling stop them – and what will be the cost to marine wildlife?

EARLIER this year, thousands of protesters gathered at Cottesloe Beach in Perth, Australia. Their message was rather surprising. "Rights, rights, rights for great whites," the crowd chanted. They were demanding an end to shark culling.

The culling – or "localised shark mitigation strategy" as some politicians prefer to call it – was prompted by seven fatal shark attacks off Western Australia since 2010, which led to a fall in tourism and leisure activities. Baited drum lines were used to catch sharks off swimming beaches last summer, with the aim of killing any great white, tiger or bull sharks longer than 3 metres. Others were released if still alive. By the end ...

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Saturday, January 24, 2015

Mice evolve better, not bigger, balls in sperm race

Size isn't everything. For decades, we've known that bigger balls are a sign that there is strong sperm competition between males. But now a laboratory experiment has shown that when many male mice mate with the same females, their descendants can quickly evolve testes that can produce more sperm even though they're not any larger.

Primate researchers in the 1970s observed that the size of an animal's testes seemed to be linked to its mating system. When many males mate with the same females, males of that species tend to have larger testes. This enables them to produce more sperm, to help them outcompete other males who might have partnered with the female and increase the chances of passing on their own genes.

"There is often a raffle element to fertilisation," says Stuart Wigby at the University of Oxford. "If you buy more tickets, you're more likely to win."

Is bigger better?

This theory of bigger being better for promiscuous species was supported by a now iconic study from 1981 that found evidence across primates.

Now, real-time evolution played out in lab-reared house mice has added a new twist to the tale.

Renée Firman at the University of Western Australia in Perth and her colleagues had previously found that, when mice evolve in conditions in which there are three females and three males, the males produce more sperm – but they somehow manage to do this without developing bigger testes.

"We were wondering how the mice had increased their sperm production in the absence of a change in testes size," says Firman.

What's inside counts

Studies by researchers like Stefan Lüpold of Syracuse University in New York and his colleagues, have suggested that there's more to it than meets the eye.

His team has found that bird species under intense sperm competition had more sperm-producing tissue in their testes. But these studies just showed a correlation between sperm competition and the density of sperm-producing tissue, and could not prove that one caused the other.

To test what was happening in mice, Firman's team put the animals in two different mating systems: a monogamous system in which males did not have to compete for females, and a polygamous one, in which males shared the same group of females – a situation closer to what would happen in the wild.

Just 24 generations later, testes from polygamous males contained more sperm-producing tissue than those of monogamous males.

More productive

"Our mouse study is the first to provide unequivocal evidence that sperm competition selects for an increase in the density of sperm-producing tissue, and consequently, increased testes efficiency," says Firman.

Lüpold agrees. "This study provides the clearest evidence so far that the level of sperm competition can affect the architecture, and likely the function, of testes, with significant changes seen after just a few generations of selection," he says.

Wigby compares the finding to brain size. Blue whales have bigger brains than humans, he says, but aren't more intelligent. "This shows that size isn't everything," he adds.

But he says that Firman's findings are unlikely to overturn our understanding of sperm competition and testes size.

"There are only so many efficiency savings a species can make. Overall, you'd still expect bigger testes in species or populations with much more sperm competition."

Journal reference: Evolution, DOI: 10.1111/evo.12603

Beautiful blood clot could reveal deadly detail

(Image: Fraser Macrae)

This is the surrealistic landscape within a blood clot, the leading cause of heart attacks and strokes. The extreme close-up, produced by Fraser Macrae from the University of Leeds, UK, using a scanning electron microscope, won the judges' prize in the annual British Heart Foundation photography competition.

The grey background represents the clot itself. The coloured blobs, added later to the original black-and-white image, highlight details within the structure. Red blood cells appear in red, platelets in turquoise, and different types of white blood cells in purple, blue, green and yellow.

Although this photo won a prize for its beauty, zooming in on blood clots can help us understand why people with heart disease have unusual clot structures that make them harder to break down.

Human ancestors got a grip on tools 3 million years ago

Move over Homo habilis, you're being dethroned. A growing body of evidence – the latest published this week – suggests that our "handy" ancestor was not the first to use stone tools. In fact, the ape-like Australopithecus may have figured out how to be clever with stones before modern humans even evolved.

Humans have a way with flint. Sure, other animals use tools. Chimps smash nuts and dip sticks into ant nests to pull out prey. But humans are unique in their ability to apply both precision and strength to their tools. It all began hundreds of thousands of years ago when a distant ancestor began using sharp stone flakes to scrape meat off skin and bones.

So who were those first toolmakers?

In 2010, German researchers working in Ethiopia discovered markings on two animal bones that were about 3.4 million years old. The cut marks had clearly been made using a sharp stone, and they were at a site that was used by Lucy's species, Australopithecus afarensis.

The study, led by Shannon McPherron of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, was controversial. The bones were 800,000 years older than the oldest uncontested stone tools, and at the time few seriously thought that australopithecines had been tool users. Plus, McPherron hadn't found the tool itself.

The problem, says McPherron, is that if we just go on tools that have been found, we must conclude that one day somebody made a beautifully flaked Oldowan hand axe, completely out of the blue. That seems unlikely.

Answers at hand

Matthew Skinner at the University of Kent in the UK and his colleagues have now found something they think is as exciting as finding an earlier tool.

They decided to look at the hands that held them. Specifically, they looked at metacarpal bones – the five bones in the palm of the hand that articulate the fingers. Because the bone ends are made of soft, spongy bone tissue, they are shaped over a lifetime of use and moulded by what that hand has done.

A chimp, for instance, spends a lot of time swinging from branches and knuckle-walking. That exerts a great deal of force on the joints in its hands, in a specific way. Skinner and his colleagues predicted how this should shape the soft bone in ape hands, then looked at modern ape bones, finding their predictions were right.

Top row: a selection of metacarpal bones. Bottom row: CT scans of the same specimens, showing the structure inside (Image: T.L. Kivell)

Modern human metacarpals looked different because we use our hands differently. Most of our activities involve some kind of pinching – think of how you hold a pencil or pick up a cup. This precision squeeze between thumb and fingers is uniquely human and a legacy from our flint-wielding ancestors.

When Skinner and his colleagues looked at the metacarpals of early human species and neanderthals – who also used stone flakes for tasks like scraping and butchering – they found bone ends that were shaped like modern human bones, and unlike ape bones.

Finally, they looked at metacarpals from four Australopithecus africanus individuals, up to 3 million years old. This revealed that their owners had been tree swingers but had also spent a lot of energy tightly pinching small objects, suggesting they were indeed early tool users.

Getting a grip

"This study is really interesting because it shows how the hand was actually used, and that's consistent with stone tool use," says McPherron.

John Hawks of the University of Wisconsin-Madison says the similarities between A. africanus and human bones are relatively convincing. "The best explanation is that the difference reflects some powerful thumb-to-finger gripping," he says.

Whether that grip was used to manoeuver delicate flakes of flint remains to be seen, though. It's possible A. africanus were using other types of tools, like bones or pieces of wood. Or they might have been using their strong precision grips to get at food in new ways, such as peeling tough skins off fruit – a task that chimps tend to do with their teeth.

But the study does suggest that 3 million years ago – 400,000 years before the oldest known Oldowan hand axes – A. africanus was already starting to use its hands differently to its ancestors. They were more dextrous and more precise. Whether or not their hands were already wrapped around flints, they were at least laying the foundations for their descendants to do so.

There's one more twist to the tale. Skinner's approach makes it possible to say something about how individual hands were used. People have found stone tools at archaeological sites, and they have found bones lying close by, but McPherron points out that no one ever finds a million-year-old hand still holding a tool. But now, it's possible to tie the stones to the hands that held them, and were shaped by them.

Journal reference: Science, DOI: 10.1126/science.1261735

Videos reveal rich upside-down world under polar ice

Video: Underwater robot reveals algae under ice

Appearances can be deceptive. At first glance, the sea ice that covers polar regions in winter seems rather barren – but clinging to the bottom of it are remarkable upside-down algal "forests" that support a wide array of creatures.

Not long ago Arctic researchers assumed phytoplankton blooms were restricted to open waters, and for good reason: the algae rely on light to survive and little of this makes it through a couple of metres of ice. A few years ago, however, researchers cruising in the Chukchi Sea between Alaska and Siberia found massive phytoplankton blooms beneath sea ice – with a biomass that was, in places, four times as much as the amount in open waters.

It's now clear that the discovery was just the tip of the iceberg. In 2014, researchers had their first opportunity for a closer look beneath the ice using a new submersible – the Nereid Under Ice Vehicle designed and built at the Woods Hole Oceanographic Institution in Massachusetts. At the American Geophysical Union meeting last month, they revealed that the submersible uncovered diverse animal communities thriving just below the ice.

"With Nereid we saw not only a big bloom of plankton but also subsequent blooms of zooplankton feeding on the phytoplankton. First copepods, then jellies and salps," says Antje Boetius at the Helmholtz Center for Polar and Marine Research in Bremerhaven, Germany. "They were concentrated in the few metres of meltwater under the ice in fantastic abundances."

Forest in bloom

The effect is something like an upside-down forest. Some algae are actually trapped in the ice, growing downwards into the water column and dangling from the surface. Other species drift in the meltwater just below the ice, forming phytoplankton blooms.

"When you think of forests, there are the trees, the shrubs, the ferns, the mosses, all active in different heights above the soil," says Boetius. Likewise, in the Arctic, the primary producers are spread across the ice column, some attached to it, others drifting right below in bits of floating or recently melted ice.

It's that stratified arrangement that might help explain why life in these upside-down forests can be so diverse and abundant. The habitats that algae growing there create soon attract microbes and small grazers – which in turn attract fish and other predators.

"It may very well be that there is undescribed animal life under the ice," says Boetius.

Similar algal communities are also showing up beneath the sea ice around Antarctica – again, thanks to new submersibles that can cruise just below the ice without disturbing it in the way a ship would. Here, though, the communities have been better studied, says Ian Hawes at the University of Canterbury in New Zealand.

Cool shades

The upside-down mats of algae provide nutrients when other options are limited, sustaining the ecosystem through lean times. "Ice algae tend to begin to grow in early spring, shortly after the sun returns and before phytoplankton in the water column below are getting enough light to do so," says Hawes.

So, the ice algal bloom is there at a time when there are few other sources of nutrients, and it is concentrated in patches, making it efficient for animals to harvest it, says Hawes.

Boetius thinks that understanding the ecology of this narrow zone under the ice may hold clues to the future of the Arctic's marine mammals and fish – and also the large predators, like polar bears, that feed on them.