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Do You Really Understand Why Water Boils? New Survey Says, Probably Not.

Good news, America: Roughly 75 percent of us know who developed the polio vaccine, that ocean tides are caused by the tugging of the moon’s gravity, and that astrology and astronomy are, in fact, different things. Phew.

Great news! The vast majority of us (86 percent) know the Earth’s core is hotter than its surface, and that if you want to make nuclear weapons, you’re going to need some uranium (82 percent of you know that, which could be somewhat concerning).

The not-so-good news: Two-thirds of you don’t understand why water boils, and figuring out what makes sounds loud is hard.

These are just some of the results released today from a science knowledge survey conducted by the Pew Research Center. Over three weeks in 2014, 3,278 people answered 12 science questions. Overall, 6 percent of respondents got a perfect score, and half answered more than eight questions correctly. Not surprisingly, the number of correct answers lined up closely with education level.

I guess that’s not so bad, especially given that some of the questions were a bit off the beaten track, like asking what a light-year measures (Time? Distance? Brightness? Weight?) or how to interpret a graph with tooth decay on one axis and sugar consumption on the other (take a guess).

Or were they? Based on these results, it might be tempting to think we can relax and stop worrying about Americans performing somewhat dismally in the sciences; but before we do that, we need to take a good look at what the Pew survey — and others like it — are really testing.

The key with such surveys, says the University of Michigan’s Jon Miller, who’s been studying science literacy for nearly four decades, is to ask questions about core concepts. Things like what molecules are, what DNA is, and how the universe is organized. Show people an image of a spiral galaxy, like the Milky Way, and ask if they know what it is and why it’s important.

Conversely, asking about names, dates, or places can tap into someone’s biographical rather than foundational knowledge. “It’s not really getting at whether they have a skill level,” Miller says.

In other words, surveys should not be testing whether people understand the headlines in today’s science stories, but whether they have enough basic knowledge to understand the headlines 20 years from now.

“What you’re not trying to do is measure, do they know what the SARS virus is, or what the West Nile virus is — but do they understand what a virus is?” Miller says. “What we should be doing is thinking about measuring the constructs that people need to know.”

Some of the questions on the Pew survey might do that. Miller points to the question about what a light-year measures (“it offers a basic structural sense of the Universe”), and the scatterplot, which tests whether people can interpret the relationship shown on a graph.

But others might be a bit more like trivia, instead offering a snapshot of this particular moment in time rather than true science comprehension. It’s a pitfall that many surveys have run into, starting with the very first one, conducted by the National Association of Science Writers in 1957. One of the survey questions asked about radioactive fallout, and which type of element commonly rained down from the sky. Would you know the answer now? Maybe not. But in the mid-20th century, Miller notes, the Nuclear Test Ban Treaty hadn’t been signed and nations were still exploding bombs overhead. So, newspapers regularly covered strontium-90 fallout.

Another example, perhaps, is a question on this year’s Pew survey. It shows a photo of a comet and asks people whether the icy object with “a tail of gas and dust that extends millions of miles” is a comet, star, asteroid, or moon. Seventy-eight percent of people answered correctly. Coincidentally, the European Space Agency’s Rosetta mission — in which a spacecraft pulled into orbit around a comet and then sent a lander to the dirtball’s surface – was heavily featured in the popular press around the time of testing (Aug. 11-Sept. 3, 2014).

One more result that might speak to this point comes from a Pew question about Jonas Salk, who developed the polio vaccine in the early 1950s. Among older adults who were alive at the time (65 years and up), 86 percent got the question right. Conversely, only 68 percent of young adults, between the ages of 18-29, got the question right.

In these cases, is it possible to disentangle actual science comprehension from biographical memories or simply reading the news? It’s not clear. And, might it be more important to understand how vaccines work and how Earth’s solar neighborhood is put together? Pew notes in its report that “how much Americans appear to know about science depends on the kinds of questions asked,” and that the survey only represents “a small slice of science knowledge.”

It would be interesting to see how the answers to these questions fluctuate over the next five years, or 10 years, and if popular science knowledge waxes and wanes like the phases of the moon…you do know how that works, right?

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Golf, Sex, and Death: Why They Don’t Get Along

He was looking down, which is what he likes to do in the forest. On his knees, squatting, peering under the leaves, and there—wedged in the mud—was the invader. The Thing From Elsewhere.

It was a golf ball.

A golf ball lying on the ground, covered in autumn foliage
Photograph by Martin Paul, Getty
Photograph by Martin Paul, Getty

David Haskell is a biology professor who recently wrote a little book about a small patch of Tennessee forest and the animals and plants that live there. Living things fascinate him. Golf balls? Not so much. “When a golf ball in the woods strikes my eyes,” he writes, “my mind condemns the ball, the golf course, the golfers, and the culture that spawns them all.”

So he’s not a fan. We’ve all met people who hate golf. Nothing new there. It’s the subtle, complicated way he hates golf—that’s what got to me.

He despises its biology.

A worker from the Las Vegas water authority xeriscapes a golf course
Photograph by Pete McBride, National Geographic Creative
Photograph by Pete McBride, National Geographic Creative

Golf, Sex, and Death

A golf course, he declares, ruthlessly erases two rhythms fundamental to the natural world: death and sex. Every golf course, he says, is designed to be sexless and deathless—and to stay that way. Which, he believes, is deeply “unnatural.”

Hmmm. Let’s think about this.

It’s true that if you step into the woods that surround a golf course, you’ll find trees that release seeds (sex!), that have pollinating flowers (sex!), and that have birds flitting about singing mating songs (sex!) and that then build nests (post-sex!). But back on the golf course, saplings, branches, nests, seeds, flowers—things that muck up the grass—are removed by the ground crew. So yes, that’s an erasure.

A manicured golf course and fall foliage
Photograph by Raul Touzon, National Geographic Creative
Photograph by Raul Touzon, National Geographic Creative

As for the grass itself, it isn’t allowed to grow to produce seed heads (sex!). Instead, it’s constantly mowed to keep it in a truncated, “youthful” state. (Haskell calls this the grassy version of “perpetual childhood”). The same goes for putting greens, where the grass is cut back even more radically and the root system is kept intentionally shallow so that it grows laterally, making for a dense, soft, youthful cover.

Botanically, I guess, Haskell is right. Evidence of aging and sex is suppressed at the golf course. But that’s also true of baseball diamonds and football fields. As for death—well, step back into the woods and everywhere you look, you see decay (rotting wood, falling leaves, the browns, reds, and yellows of autumn). Death and dying are everywhere.

For example, tree stumps. A tree takes roughly the same time to disintegrate as it does to reach its full height. So in any patch of woods, dead trees stick around, showing off their “dead verticality,” as the poet Gary Snyder once put it.

“How curious it would be to die and then remain standing for another century or two,” Snyder said. “If humans could do it, we’d hear news like, ‘Henry David Thoreau finally toppled over.’”

But there is no toppling on a golf course. Everything is too young to topple. Old things are removed. “The golf course has been sanitized,” Haskell writes, “by the puritan life-police.” Be young or be gone.

A golf ball in the grass at the Hard Rock Golf Course in Punta Cana
Photograph by Raul Touzon, National Geographic Creative
Photograph by Raul Touzon, National Geographic Creative

This is the deep mindset of golf course design—which is strange, since (unlike baseball and football) it is famously a game that attracts 50-, 60-, and 70-year-olds. Why protect them from what they already know? Ah, well, maybe that’s the key. Maybe a golf course is a “Don’t Ask, Don’t Tell” stage set designed to soothe folks who don’t want to be reminded of what’s coming and what’s waning.

The forest is different. It’s orchestral. It emerges, writes Haskell, “from the give and take of thousands of species; a golf course’s ecological community is a monoculture of alien grass that emerged from the mind of just one species.” The one species that can see death coming.

What to Do With the Invading Golf Ball?

So when David Haskell finds a golf ball in his forest patch, he gets rid of it, right? He’s going to do what the golfers do—he will sanitize.

Ah. Not so fast. Haskell is a complicated man.

“Should I remove the balls or leave them nestled in place?” he asks himself. They’re not going to decompose any time soon. Golf balls are strengthened thermoplastic, which means they can’t be eaten by bacteria or fungi. Biologically, they “have nothing to contribute,” Haskell writes, and yet (you can feel him struggling here), what’s the point of removing the ball? Yes, taking it away removes evidence of human influence, but humans are constantly visiting, altering, shaping the woods. We hunt, we chop, we crush, we litter, we pee in the woods. Are we invaders? Is that the right word?

“Such a view drives a wedge between humanity and the rest of the community of life,” Haskell writes. Instead, he looks down at the ball and thinks, “A golf ball is the manifestation of the mind of a clever, playful African primate. This primate loves to invent games to test its physical and mental skill. Generally, these games are played on carefully reconstructed replicas of the savanna from which the ape came and for which its subconscious still hankers. The clever primate belongs in this world. Maybe the primate’s productions do also.”

OK, so the golf ball is a human dropping. But it’s also a lost ball, out of bounds. So what does he do? To pluck or not to pluck? Haskell gives it one last ponder. And then walks away.

The ball stays.

“(T)o love nature and to hate humanity is illogical,” he writes. “Humanity is part of the whole … Nature does not need to be cleaned of human artifacts to be beautiful.”

Golf courses, on the other hand, need to cleaned of woodland artifacts to be beautiful.

Interesting difference.

David Haskell’s wonderful book The Forest Unseen: A Year’s Watch in Nature has been mentioned here before, but it taught me so many things about trees, leaves, light, snails, flowers, little mammals, twigs, buttercups, photons, and on and on, I haven’t stopped thinking about it. It’s not like I don’t read other books, I just can’t stop thinking about this one.

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George Washington’s Oh-So-Mysterious Hair

That hair you’ve seen so many times on the dollar bill? That hair he’s got crossing the Delaware, standing by a cannon, riding a horse in those paintings? His hair on the quarter? On all those statues? The hair we all thought was a wig? Well, it wasn’t a wig. “Contrary to a common belief,” writes biographer Ron Chernow in his Pulitzer Prize-winning Washington: A Life, George Washington “never wore a wig.”

I’m stunned.

Illustration of George Washington on a quarter
Illustration by Wendy MacNaughton
Illustration by Wendy MacNaughton

Turns out, that hair was his. All of it—the pigtail, the poofy part in the back, that roll of perfect curls near his neck. What’s more (though you probably already guessed this), he wasn’t white-haired. There’s a painting of him as a young man, with Martha and her two children, that shows his hair as reddish brown, which Chernow says was his true color.

Picture of a painting of George Washington with Martha Washington and her two children
The Courtship of Washington, John C. McRae, 1860 Image Courtesy of the Mount Vernon Ladies’ Association

The whiteness was an effect. Washington’s hairstyle was carefully constructed to make an impression. It wasn’t a sissyish, high-society cut. It was, back in the 1770s and 1780s, a military look, something soldiers or want-to-be soldiers did to look manly. “However formal it looks to modern eyes,” Chernow writes, “the style was favored by military officers.”

Illustration of George Washington in profile, emphasizing his long hair, which is down in this illustration
Illustration by Wendy MacNaughton
Illustration by Wendy MacNaughton

Think of this as the 18th-century equivalent of a marine buzz cut. In Washington’s time, the toughest soldiers in Europe, officers in the Prussian Army, fixed their hair this way. It was called a queue. British officers did it too. So did British colonials in America.

Here’s how it worked. Washington grew his hair long, so that it flowed back toward his shoulders.

Illustration of George Washington in profile, showing his hair being gathered before putting it into a ponytail
Illustration by Wendy MacNaughton
Illustration by Wendy MacNaughton

Then he’d pull it firmly back, broadening the forehead to give him, Chernow writes in his biography, “an air of martial nobility.” The more forehead, the better. Nowadays we notice chins. But not then. Foreheads conveyed force, power.

The look was achieved with appropriate muscularity. In the British Army a tough hair yank was a rite of passage for young officers; it was common to yank really hard.

Illustration of George Washington in profile, showing his hair being pulled backwards before being put into a ponytail
Illustration by Wendy MacNaughton
Illustration by Wendy MacNaughton

A military journalist, Joachim Hayward Stocqueler, describes a British soldier from that time who says his hair and skin was pulled so fiercely, he didn’t think he’d be able to close his eyelids afterward.

Once gathered at the back, hair was braided or sometimes just tied at the neck by a strap or, on formal occasions, a ribbon. Washington would occasionally bunch his ponytail into a fine silk bag, where it would bob at the back of his head.

Illustration of George Washington in profile, showing his hair tied in a bow
Illustration by Wendy MacNaughton
Illustration by Wendy MacNaughton

Then he would turn to his side hairs, which he “fluffed out,” writes Chernow, “into twin projecting wings, furthering the appearance of a wig.” George Washington “fluffing out”? That’s such an odd image. Artist Wendy MacNaughton, my partner in crime, sees it this way:

Illustration of George Washington in profile, emphasizing his curled hair
Illustration by Wendy MacNaughton
Illustration by Wendy MacNaughton

You should close your eyes and see him fluffling in your own way.

Next question: How did those side curls stay curled? Betty Myers, master wigmaker at Colonial Williamsburg in Virginia, wrote to me that it was common to grease one’s hair with pomade. Oily hair helped. We don’t know how often Washington shampooed, but the less he showered, the firmer his fluffs.

And now, to the whiteness. Washington’s hair wasn’t splotchy. It was like a snow-covered mountain, evenly white. This was accomplished by sprinkling a fine powder on the head. There were lots of powders to choose from, writes Myers, including “talcum powder, starch, ground orris root, rice powder, chalk, [or] even plaster of paris …” Washington probably used a finely milled (expensive) product, which was applied, cloud-like, to his head. To keep from gagging in a powder fog, it was common to cover the face with a cone of coiled paper, like this:

Illustration of George Washington covering his face with a cone while he powders his hair
Illustration by Wendy MacNaughton
Illustration by Wendy MacNaughton

The powder was sometimes applied with a handheld bellows. An attendant would pump a cloud of powder from a small nozzle and let it settle on the hair. But Washington, says biographer Ron Chernow, would dip a puff, a snakelike bunch of silk striplings—into a powder bag, then do a quick shake over his bent head. Maybe a slave would do this for him. When being powdered, it was traditional to wear a “powdering robe,” basically a large towel tied around the neck, to keep from being doused.

Picture of a drawing of a woman having her wig powdered
Photo by Hulton Archive/Getty Images
Circa 1750, A political cartoon entitled 'The English Lady in Paris, an Essay on Puffing by Louis le Grande', showing a seated old lady having her wig powdered by a nasty looking Frenchman. (Photo by Hulton Archive/Getty Images)

Which leaves one last puzzle. Washington was a careful, self-conscious dresser. When he appeared at the first Continental Congress, he was the only important delegate to wear a military costume, choosing, Chernow writes, the “blue uniforms with buff facings and white stockings” of the Virginia citizen militia while adding his own “silk sash, gorgets, [and] epaulettes.” Later, he’s described dancing at balls in black velvet. So if Washington liked dark clothes, how’d he keep the powder from showing? The man would have been covered in dandruff-like sprinkles. (Editor’s Note: One of our readers, Mike Whybark, shared a painting that makes me wonder … Maybe his shoulders did look a little snowed-on.) Myers, the wig scholar, says that’s why Washington bunched his ponytail into a silk bag, to keep from leaving a white windshield wiper splay of powder on his back when he was dancing with the ladies (which he liked to do). As for keeping the powder off one’s shoulders, how Washington did that—if he did do that—nobody could tell me. Probably every powder-wearing guy in the 1760s knew the secret, but after a couple of centuries, whatever Washington did to stay spotless is lost to us.

Illustration of George Washington, on the left, with white powder on his houlders, and on the right without white powder on his shoulders
Illustration by Wendy MacNaughton
Illustration by Wendy MacNaughton

We can stare all we like at his shoulders and wonder, but the truth is, there are some things about our first president we may never, ever know.

Illustration of George Washington winking with his hair perfectly fixed
Illustration by
Wendy MacNaughton
Illustration by Wendy MacNaughton

Wendy MacNaughton draws people, cats, bottles, scenes, faces, places. If, totally out of the blue, I call her and say, “Can you imagine Leonardo da Vinci’s personal notebook or George Washington getting his hair done?” she just giggles and draws. And a week later, I’m doing a happy dance. If you want to see what she’s up to right now, you’ll find more of her work here. And if you enjoy presidential hair stories, here’s the other Big Guy, Abe Lincoln, on a day in 1857 when he clearly lost his comb. Hairstylists shouldn’t look—it’s too scary.

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World’s Oldest Murder Mystery Was 430,000 Years in the Making

The first known murder was just as brutal as any other. The attacker smashed the victim twice in the head, leaving matching holes above the victim’s left eyebrow. The dead body was then dropped down a 43-foot shaft into a cave—where it lay for nearly half a million years.

Talk about your cold case.

Paleontologists pieced together the 430,000-year-old skull and reported their forensic analysis Wednesday in the journal PLOS ONE. Injuries to the skull represent the oldest direct evidence of homicide, the scientists say.

As for whether this was the first murder ever to occur, “for sure that’s not the case,” says Nohemi Sala, lead author of the study. The scientists can describe this victim as a young adult, but the age and even gender are unknown.

“In the fossil record, there are many cases of traumatic injury, but not a lot of evidence of killing,” says Sala, a paleontologist at the Instituto de Salud Carlos III in Madrid.

That doesn’t mean killing was uncommon before modern times, of course, but fossilized remains of any kind are relatively rare so far back.

The last several tens of thousands of years, on the other hand, are littered with grisly scenes. Take the case of Shanidar-3, a Neanderthal who lived about than 50,000 years ago. A cut on one of his left ribs shows that Shanidar-3 was probably killed by a spear, making him perhaps the oldest known murder victim prior to the new find.

The latest skull comes from the Sima de los Huesos, or “Pit of Bones,” site in Spain, where paleontologists have found the remains of at least 28 individuals. Who were these people? Well, they weren’t modern humans, and they weren’t really Neanderthals either.

Exactly what to call the Sima de los Huesos people has been debated, but Sala and her colleagues identify them as members of the species Homo heidelbergensis, an early human ancestor that gave rise to the Neanderthals.

Cause of death

To figure out whether the skull fractures resulted from blows or from the fall down the cave shaft, the team compared the injuries to those from modern cases of violence and falls. A face-to-face attack with a blunt instrument best fits the pattern of injury, the scientists say. The bones showed no evidence of healing, so the victim probably died immediately or soon after the attack.

© Javier Trueba/Madrid Scientific Films, from Arsuaga et al/Science 2014
The “Pit of Bones” cave in Spain. © Javier Trueba/Madrid Scientific Films, from Arsuaga et al/Science 2014
The remains of 28 individuals who lived over 400,000 years ago were found in this cave, the "Pit of Bones" in Spain.

What’s more, the two holes in the skull are the same shape and appear to have been made by the same weapon. It’s very unlikely that an accidental fall onto a rock would produce two nearly identical skull fractures, the team says.

The weapon

Sala says the weapon was probably “something very hard,” but we’ll never know if it was made of wood or rock, or something else.

The scientists scoured the site, she says, but didn’t turn up any potential murder weapons. There was only stone tool found at the site, and it wasn’t the right shape.

The motive

Another unsolved mystery: what drove an ancient person to kill. “Life was hard in the past,” Sala says, so there could have conflicts over resources or any number of reasons for a fight.

Even with difficult lives, though, Sala describes the Sima de los Huesos people as caring for one another. “There were 28 individuals at the site of different ages,” she says. “We know that some of these people had health problems. One person had very serious pathology in the lower back and probably had troule walking and moving.” Someone had to be caring for these people before their deaths, she says.

And while it might not sound like a lovely funeral today, the fact that people living at the site buried bodies by dropping them down the same shaft indicates some sense of ceremonial burial or ritual—the dead weren’t merely dragged away from the campsite to decay.

Overall, the site paints a picture of ancient people who lived, loved—and sometimes fought—together.

Sala’s take on life with Homo heidelbergensis: “They’re not so bad—at least they have also good points.”



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United We Improve

Humans see further by standing on the shoulders of giants. We build upon the cultures, skills, technologies and knowledge of past generations, in a way that other animals do not.

Many scientists have suggested that this cumulative culture depends on the size of our groups. The more of us there are, the faster our culture ratchets upwards in complexity. If our populations shrink, we lose skills and tech. We see this in theoretical models. We see it in past civilisationsTasmania being the classic example.

And now, we can see it in two experiments. Working independently, two groups of scientists have shown that larger, more sociable groups are indeed better at maintaining complex cultural traditions, and even improving on them.

This might seem obvious, but people forget about it. As Joe Henrich, who led one of the new studies, told me, many scientists have assumed that Neanderthals were less intelligent than modern humans because they built less complex tools. The alternative is that they just lived in smaller, more scattered groups, and lacked the cultural ratchet that our ancestors had because of their big, connected societies.

As Henrich said: “For producing fancy tools and complexity, it’s better to be social than smart. And things that make us social are going to make us seem smarter.”

I’ve covered the two studies over at Nature News. Head over there for the details.

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What tree-climbing pygmies tell us about foot evolution

At some point in human history, our ancestors descended from the trees and started walking permanently on two legs. In the process, our feet evolved from the grasping appendages of other apes into sturdy levers. We lost an opposable big toe, our ankles became stiffer, and our bones formed an arch that runs from our ankle to our toes. We sacrificed the ability to grip in return for a springy, shock-absorbent step.

These changes were already in place 3.5 million years ago. One of our ancient relatives, Australopithecus afarensis, had a remarkably human foot and was clearly already walking around on two legs. Some scientists have taken this to mean that hominins such as Lucy (the most famous A.afarensis specimen) necessarily walked on the ground. After all, human feet are supposedly ill-suited for life in the trees.

But try telling that to the gentleman in the video below. He’s one of the Twa pygmies—a group of Ugandan hunter-gatherers who often climb trees in search of food, such as honey and fruit. Like other Twa men, he started from an early age. And he’s clear proof that a human foot is no impediment to walking straight up a trunk.

The footage was shot by Vivek Venkataraman, Thomas Kraft and Nathaniel Dominy from Dartmouth College. The trio originally started studying the Twa to understand the evolution of their short five-foot stature but were awestruck at how adeptly they could climb. “We tried to climb the same trees, but we found it extremely difficult,” says Venkataraman. “The Twa were quicker, more agile, and highly coordinated.”

That’s because their ankles are so extraordinarily flexible that their feet can make up to 45 degree angles with their shins. You can clearly see this in the video. It’s a level of flexibility comparable to wild chimpanzees, which walk up trees in much the same way. They plant their soles flat against the trunk, allowing them to hold their bodies closer to the trees and reducing the energy it takes to climb.

For comparison, most people can only bend their feet by 15 to 20 degrees. If you or I tried to match the flexion of a Twa climber, our ankles would rupture catastrophically and we wouldn’t be walking, much less effortlessly scaling a thick vine.

From Venkataraman et al, 2013

But the Twa’s secret isn’t in their ankles, which are indistinguishable from those of other people. Instead, the team found that the Twa’s flexibility stems from calf muscles (gastrocnemius) with unusually long fibres—far longer than those of the Bakiga, a group of neighbouring Ugandan farmers who don’t climb trees. The team found the same differences in the Philippines. The tree-climbing Agta hunter-gatherers have far longer gastrocnemius fibres than the non-climbing Manobo farmers.

Venkataraman suspects that their calf muscles aren’t born this way. Instead, their fibres lengthen with practice. “People who frequently wear high heels have short calf muscle fibres, and their ankles are stiffer as a result,” he says. Regular tree-climbing does the opposite for the Twa.

The stark lesson from this hard-won research is that there’s nothing about a human foot that precludes us from the trees. And equally, the fact that A.afarensis had a human-like foot doesn’t mean that it was a bad climber. The muscles, which don’t fossilise, can make a huge difference. With the right calves, Lucy could have scampered up a trunk as well as striding across a savannah.

Lucy at the Smithsonian Natural History Museum., by Ryan Somma

Venkataraman’s study lobs some much-needed data into a longstanding debate about how A.afarensis actually moved. “Our field has been arguing about tree climbing in A.afarensis for 30 years,” says Jeremy DeSilva from Boston University. “Remarkably, this is the first study to thoroughly investigate the tree-climbing habits of its closest living relative: humans! It is not that no one ever thought to do this; data such as these are just very difficult to obtain.”

The study helps to make sense of some A.afarensis’s contrasting anatomy—it had the feet of a committed biped, but the long arms, curved fingers, and ape-like shoulder blades of a competent tree-climber. “[It adds] to the growing body of evidence that the supposedly unique human foot is not quite as distinct from that of other great apes as we have tended to believe, and that human bipedalism had arboreal origins,” says Robin Crompton from the University of Liverpool.

Of course, Venkataraman’s study doesn’t mean that A.afarensis climbed trees, just that we shouldn’t rule out that possibility on the basis of its bones. “Maybe not having an opposable big toe isn’t as catastrophic for climbing trees as we commonly assume, especially if you change your climbing style,” he says.

“My guess is that the A.afarensis was mostly a terrestrial biped, living and feeding on the ground. At night, I suspect that they may have climbed slowly and carefully into the trees to build night nests,” says DeSilva. “But that scenario is really tough to test without more fossils and a better idea of what anatomies allow an upright walker to safely and effectively climb a tree.”

Update: A last-minute comment. Claude Owen Lovejoy from Kent State University says that the study misses the point. “No one has ever claimed that A.afarensis did not climb trees. I’m sure they did. Modern humans climb trees, but so what? The argument is not about behaviour but about principal adaptation.” And that was for bipedality. “Bipedality was so central to A.afarensis’ adaptation even if it climbed trees regularly,” says Lovejoy.

Reference: Venkataraman, Kraft & Dominy. 2012. Tree climbing and human evolution. http://dx.doi.org/10.1073/pnas.1208717110

More on human evolution:

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Wormholes in old books preserve a history of insects

Absence can speak volumes. The lack of sediment in a flat piece of ground—a track—can testify to the footstep of a dinosaur that once walked on it. The lack of minerals in a solid shell—a hole—can reveal the presence of parasite that was once trapped in it. The world’s museums are full of such “trace fossils”, but so are many of the world’s art galleries.

The image above is taken from a woodcut currently residing in Amsterdam’s Rijksmuseum. It was made by etching a pattern into a block of wood, so that the remaining raised edges could be dipped in ink and used to print an image. These woodcuts were the main way of illustrating European books between the 15th and 19th centuries, and were used for at least 7 million different titles.

But as you can see, the print is littered with tiny white holes. These are called wormholes, and inaccurately so—they’re actually the work of beetles. The adults laid their eggs in crevices within the trunks of trees. The grubs slowly bored their way through the wood, eventually transformed into adults, and burrowed their way out of their shelters. The artists who transformed the tree trunks into printing blocks also inherited the exit-holes of the adult beetles, which left small circles of empty whiteness when pressed onto pages.

The beetles only emerged a year or so after the blocks were carved. The holes they left must have been frustrating, but remaking them would have been expensive. So the blocks were kept and reused despite their defects, unless the beetles had really gone to town. The holes they left behind preserve a record of wood-boring beetles, across four centuries of European literature. These holes are trace fossils. They’re evidence of beetle behaviour that’s been printed into old pages, just as dinosaur tracks were printed into the earth.

Now, Blair Hedges from Pennsylvania State University has used these fossils to study the history of the beetles that made them.


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Editing women into Wikipedia

Last Friday, a group of volunteers gathered in the Royal Society in London to edit female scientists into the history books—or at least, into Wikipedia. Their goal was to start fixing the online encyclopaedia’s comparatively thin information about women in science and technology.

I attended the “edit-a-thon”, reporting for Nature. Before I turned up, I wondered about the rationale behind holding a specific event to edit Wikipedia, which can be done at any time and place. I also wondered how much the editors could accomplish in just 3.5 hours. Both concerns were addressed on the day, and in the piece. Take a look. Also, there was an Ada Lovelace/Wikipedia cake.

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At the bottom of a Japanese lake, the key to more accurate carbon-dating

Carbon-dating is a widely used technique that allows us to gauge the age of archaeological samples from up to 60,000 years ago. But it’s not a straightforward method.

It relies on a radioactive version of carbon called carbon-14, which is formed in the atmosphere and is taken up by plants (and whatever eats the plants). Once these die, the carbon-14 in their bodies decays away at a steady, predictable rate. By measuring it, we can calculate how old an ancient sample is.

But there’s a catch. The levels of carbon-14 in the atmosphere vary from year to year, so scientists need some way of assessing these fluctuations to correct their estimates. They need long-running timetables, where each year in the past several millennia can be “read”, but where true levels of atmospheric carbon-14 can be measured.

And now, in the bottom of a Japanese lake, scientists have found the best such timetable yet. As I write in The Scientist:

The sediment of a Japanese lake has preserved a time capsule of radioactive carbon, dating back to 52,800 years ago. By providing a more precise record of this element in the atmosphere, the new data will make the process of carbon-dating more accurate, refining estimates by hundreds of years.

The data will allow archaeologists to better gauge the age of their samples and estimate the timing of important events such as the extinction of Neanderthals or the spread of modern humans through Europe.

“It’s like getting a higher-resolution telescope,” said Christopher Bronk Ramsey from the University of Oxford, who led the study. “We can look [with] more detail at things [such as] the exact relation between human activity and changes in climate.”

Head over there for more.

Image by Christopher Bronk Ramsey

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A 61-million-person experiment on Facebook shows how ads and friends affect our voting behaviour

On November 2nd, 2010, more than 61 million adults visited Facebook’s website, and every single one of them unwittingly took part in a massive experiment. It was a randomised controlled trial, of the sort used to conclusively test the worth of new medicines. But rather than drugs or vaccines, this trial looked at the effectiveness of political messages, and the influence of our friends, in swaying our actions. And unlike most medical trials, this one had a sample size in the millions.

It was the day of the US congressional elections. The vast majority of the users aged 18 and over (98 percent of them) saw a “social message” at the top of their News Feed, encouraging them to vote. It gave them a link to local polling places, and clickable button that said “I voted”. They could see how many people had clicked the button on a counter, and which of their friends had done so through a set of randomly selected profile pictures.

But the remaining 2 percent saw something different, thanks to a team of scientists, led by James Fowler from the University of California, San Diego. Half of them saw the same box, wording, button and counter, but without the pictures of their friends—this was the “informational message” group. The other half saw nothing—they were the “no message” group.

By comparing the three groups, Fowler’s team showed that the messages mobilised people to express their desire to vote by clicking the button, and the social ones even spurred some to vote. These effects rippled through the network, affecting not just friends, but friends of friends. By linking the accounts to actual voting records, Fowler estimated that tens of thousands of votes eventually cast during the election were generated by this single Facebook message.


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Why did people start mummifying their dead in the driest place on Earth?

One does not simply start mummifying one’s dead. Mummification is a technically challenging business that involves sophisticated tricks for preparing a corpse. It’s also steeped in intricate cultural traditions. How does such a practice start?

Chilean scientist Pablo Marquet has tried to answer that question by studying the world’s oldest mummies – those created by the Chinchorro people of northern Chile. The Chinchorro were preserving their dead some two thousand years before the Egyptians started doing so. Rather than just mummifying their elites, the Chinchorro preserved all of their dead – man and woman, elderly and infants. They went to great pains to do so. They would remove the organs and muscles of their dead, reinforce the skeletons with sticks, and fill the bodies with earth and vegetation to get the right shape.  They covered the body in a mud coat and clay mask, and decorated it with colour.

Marquet thinks he knows why these practices began. Rather than simply looking at cultural factors, he has intimately tied the practice into changing climates and shifting population sizes. At the time that they started mummifying cadavers, the Chinchorro had gone through a population boom, driven by rich coastal seas. But they also lived in the Atacama Desert: the so-called driest place on Earth. In such an arid environment, any buried corpses would have taken their time to decay, if they did at all. The very land around them naturally mummified the corpses, and the Chinchorro simply followed suit.


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British family’s problems hint at a gene involved in linking language and meaning

We’ve all had that annoying feeling when we fail to find a word that’s just at the tip of our tongues. Usually, these moments are passing nuisances, but they are a more severe impediment for a British family known as JR. Eight of them suffer from an unusual problem with “semantic cognition” – the ability to bind words to their meanings during thought or communication.

They can’t remember words, names, or topics of conversation – all of us get this, but the JR family experiences a more extreme version. They make errors in everyday conversations when they use words with related meanings in the wrong places. Their comprehension falters to the extent that reading books or following films is hard work.

These difficulties have caused them much social anxiety, and hampered their ability to cope with school and work. But for scientists, they are undeniably exciting because they seem to stem from a single errant gene. If that’s the case, the gene apparently affects the intertwining of concepts and language, but not any other mental abilities – the affected family members are otherwise intelligent and articulate. The JR family could lead us to new insights about language, thought and memory, just as similar families have done in the past.


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Tunes without composers: music naturally evolves on DarwinTunes

The tunes embedded above weren’t written by a composer, but fashioned through natural selection. They are the offspring of DarwinTunes, a program which creates bursts of noise that gradually evolve based on the preferences of thousands of human listeners. After hundreds of generations, tracks that are boring and grating soon morph into tunes that are really quite rhythmic and pleasant (even if they won’t be topping charts any time soon).

DarwinTunes is the brainchild of Robert MacCallum and Armand Leroi from Imperial College London. “We suspected that musical styles evolve through Darwinian natural selection,” says MacCallum. “They are copied and modified from artist to artist and generation to generation, with popular styles more likely to be copied as they get more exposure. “ The duo created DarwinTunes to see if music could actually evolve in this way.

The DarwinTunes tracks are all 8-second-long loops, each encoded by a ‘digital genome’ – a program that determines which notes are used, where they’re placed, the instruments, the tempo, and so on. The genomes of two parent loops can shuffle together in random ways to produce daughter loops, which also develop small random mutations. This mimics the way in which living things mate and mutate. It also mimics the way in which composers merge musical styles together, while inventing new motifs.

The experiment began with 100 randomly generated loops. On the DarwinTunes website, listeners could listen to these and rate them on a five-point scale, from “I can’t stand it” to “I love it”. Every time 20 loops were rated, the top 10 pair off, mate with each other to produce two daughters, and die. At any time, there are only 100 loops in the total population.

To date the loops have been evolving for 3,060 generations, and over 50,000 of them have been born. By taking loops from DarwinTunes’ entire history and asking volunteers to rate them, MacCallum and Leroi showed that they became more appealing with time. For example, they were more likely to contain chords found in Western music and they contained more complex rhythms. “We hoped for slightly more “advanced” music, but were very happy with the results,” says MacCallum.

This upward rise in appeal only lasted for 500 or 600 generations. After that, the loops hit a plateau and apparently stopped evolving. MacCallum and Leroi think that this is because the loops become so complex that their intertwining melodies and rhythms don’t merge very well. The act of mating, rather than combining the best of both parents, ends up splitting up elements that work well together.

Alternatively, it may be that as the loops become well adapted to the tastes of their listeners, it becomes harder to change them without messing something up – they become trapped in an adaptive peak, unable to reach a new peak without first crossing into a valley. Both of these processes have their counterparts in the world of real genetics. MacCallum and Leroi argue that this might explain why many old musical styles tend to be very conservative, changing little over thousands of years.

DarwinTunes is the latest in a line of digital evolution programs, where computer code copies itself, mutates, evolves and adapts. For example, in The Blind Watchmaker, Richard Dawkins describes a programme of the same name that can evolve complex shapes from initially simple collections of lines. These programs never fully reflect the reality of evolution, but they allow scientists to ask basic questions about evolution in a controlled way. They can set up controlled experiments, repeat them, replay evolution from specific points, and analyse how specifically their artificial creations have changed. It’s incredibly hard (but not impossible) to do that with actual living things.

But Michael Scott Cuthbert, who works on computer-aided musical analysis at MIT, is sceptical that the approach tells us anything about the evolution of music. “They have shown that people can sense a glimmer of the things they like about music even when most of it consists of sounds they hate,” he says.  “But it doesn’t give any information about why music sounded differently in the past, why people like different things today, or how music might evolve in the future.”

“Suppose you randomly threw car parts into piles and asked people to rate those they’d most like to buy,” he says. “Then you took parts from the highest-rated heaps, and rearranged them into new heaps.  People might hate all of them at first, but they’d probably rate the ones with four tires or a trunk in the back or a steering wheel in the drivers’ seat higher than the rest. Do that long enough and I wouldn’t be surprised that you’d eventually get something that looked like a 2011 Honda Civic.  But that doesn’t mean that that’s how a car is made.”

MacCallum and Leroi acknowledge that real music changes in a more complex way than DarwinTunes currently captures. Composers write music with their own intentions, while listeners choose music based not just on what it sounds like, but on whether other people like it too. DarwinTunes could be changed to include these dynamics – volunteers could combine the loops themselves, and listeners could see earlier ratings.

“The big question for me is can we bring the quality up a level where you don’t have to be curious about the science to take part?” says MacCallum. “We can do that if we had millions of users, and segregated them based on musical genre preferences.  It’s a chicken and egg problem though!”

Reference: MacCallum, Mauch, Burt & Leroi. 2012. Evolution of music by public choice. PNAS http://dx.doi.org/10.1073/pnas.1203182109

Image by Pedro Sanchez

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Why humans stand on giant shoulders, but chimps and monkeys don’t

We are like dwarves standing on the shoulders of giants. This metaphor, famously used by Isaac Newton, describes how humans build on what has come before. Everything in our culture is the result of knowledge and skills that have slowly accumulated over time. Without this “cumulative culture”, we wouldn’t have our deep scientific knowledge, rich artistic traditions, or sophisticated technology. Simply put, you can’t make a car from scratch – first, you need to invent the wheel.

Are we alone in this respect? Certainly, many other animals can learn knowledge and skills from each other, and many of them have cultural traditions. But Newton’s metaphor involves not just the spread of knowledge, but its gradual improvement. We build on the past, rather than just passing it along. As generations tick by, our culture becomes more complex. Do other species show the same ‘cultural ratchet’?

Lewis Dean from the University of St Andrews tried to answer that question by presenting human children, chimpanzees and capuchin monkeys with the same task: a puzzle box with three, increasingly difficult stages, each one building on the last.


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Violinists can’t tell the difference between Stradivarius violins and new ones

Antique Italian violins, such as those crafted by Antonio Stradivari or Giuseppe Guarneri “del Gesu”, can fetch millions of dollars.  Many violinists truly believe that these instruments are better than newly made violins, and several scientists have tried to work out why. Some suspected at the unusually dense wood, harvested from Alpine spruces that grew during an Ice Age. Others pointed the finger at the varnish, or the chemicals that Stradivari used to treat the wood.

But Claudia Fritz (a scientist who studies instrument acoustics) and Joseph Curtin (a violin-maker) may have discovered the real secret to a Stradivarius’s sound: nothing at all.

The duo asked professional violinists to play new violins, and old ones by Stradivari and Guarneri. They couldn’t tell the difference between the two groups. One of the new violins even emerged as the most commonly preferred instrument.