In Neanderthal DNA, signs of a mysterious human migration

Carl Zimmer writes: With fossils and DNA, scientists are piecing together a picture of humanity’s beginnings, an origin story with more twists than anything you would find at the movie theater.

The expert consensus now is that Homo sapiens evolved at least 300,000 years ago in Africa. Only much later — roughly 70,000 years ago — did a small group of Africans establish themselves on other continents, giving rise to other populations of people today.

To Johannes Krause, the director of the Max Planck Institute for Human History in Germany, that gap seems peculiar. “Why did people not leave Africa before?” he asked in an interview. After all, he observed, the continent is physically linked to the Near East. “You could have just walked out.”

In a study published Tuesday in Nature Communications, Dr. Krause and his colleagues report that Africans did indeed walk out — over 270,000 years ago.

Based on newly discovered DNA in fossils, the researchers conclude that a wave of early Homo sapiens, or close relatives of our species, made their way from Africa to Europe. There, they interbred with Neanderthals.

Then the ancient African migrants disappeared. But some of their DNA endured in later generations of Neanderthals.

“This is now a comprehensive picture,” Dr. Krause said. “It brings everything together.” [Continue reading…]

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Why your brain hates other people — and how to make it think differently

Robert Sapolsky writes: As a kid, I saw the 1968 version of Planet of the Apes. As a future primatologist, I was mesmerized. Years later I discovered an anecdote about its filming: At lunchtime, the people playing chimps and those playing gorillas ate in separate groups.

It’s been said, “There are two kinds of people in the world: those who divide the world into two kinds of people and those who don’t.” In reality, there’s lots more of the former. And it can be vastly consequential when people are divided into Us and Them, ingroup and outgroup, “the people” (i.e., our kind) and the Others.

Humans universally make Us/Them dichotomies along lines of race, ethnicity, gender, language group, religion, age, socioeconomic status, and so on. And it’s not a pretty picture. We do so with remarkable speed and neurobiological efficiency; have complex taxonomies and classifications of ways in which we denigrate Thems; do so with a versatility that ranges from the minutest of microaggression to bloodbaths of savagery; and regularly decide what is inferior about Them based on pure emotion, followed by primitive rationalizations that we mistake for rationality. Pretty depressing.

But crucially, there is room for optimism. Much of that is grounded in something definedly human, which is that we all carry multiple Us/Them divisions in our heads. A Them in one case can be an Us in another, and it can only take an instant for that identity to flip. Thus, there is hope that, with science’s help, clannishness and xenophobia can lessen, perhaps even so much so that Hollywood-extra chimps and gorillas can break bread together. [Continue reading…]

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Daniel Everett: Becoming human without words for colors, numbers, or time

 

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Oldest Homo sapiens bones ever found shake foundations of the human story

The Guardian reports: Fossils recovered from an old mine on a desolate mountain in Morocco have rocked one of the most enduring foundations of the human story: that Homo sapiens arose in a cradle of humankind in East Africa 200,000 years ago.

Archaeologists unearthed the bones of at least five people at Jebel Irhoud, a former barite mine 100km west of Marrakesh, in excavations that lasted years. They knew the remains were old, but were stunned when dating tests revealed that a tooth and stone tools found with the bones were about 300,000 years old.

“My reaction was a big ‘wow’,” said Jean-Jacques Hublin, a senior scientist on the team at the Max Planck Institute for Evolutionary Anthropology in Leipzig. “I was expecting them to be old, but not that old.”

Hublin said the extreme age of the bones makes them the oldest known specimens of modern humans and poses a major challenge to the idea that the earliest members of our species evolved in a “Garden of Eden” in East Africa one hundred thousand years later.

“This gives us a completely different picture of the evolution of our species. It goes much further back in time, but also the very process of evolution is different to what we thought,” Hublin told the Guardian. “It looks like our species was already present probably all over Africa by 300,000 years ago. If there was a Garden of Eden, it might have been the size of the continent.” [Continue reading…]

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What hyenas can tell us about the origins of intelligence

David Z. Hambrick writes: Physical similarities aside, we share a lot in common with our primate relatives. For example, as Jane Goodall famously documented, chimpanzees form lifelong bonds and show affection in much the same way as humans. Chimps can also solve novel problems, use objects as tools, and may possess “theory of mind”—an understanding that others may have different perspectives than oneself. They can even outperform humans in certain types of cognitive tasks.

These commonalities may not seem all that surprising given what we now know from the field of comparative genomics: We share nearly all of our DNA with chimpanzees and other primates. However, social and cognitive complexity is not unique to our closest evolutionary cousins. In fact, it is abundant in species with which we would seem to have very little in common—like the spotted hyena.

For more than three decades, the Michigan State University zoologist Kay Holekamp has studied the habits of the spotted hyena in Kenya’s Masai Mara National Reserve, once spending five years straight living in a tent among her oft-maligned subjects. One of the world’s longest-running studies of a wild mammal, this landmark project has revealed that spotted hyenas not only have social groups as complex as those of many primates, but are also capable of some of the same types of problem solving.

This research sheds light on one of science’s greatest mysteries—how intelligence has evolved across the animal kingdom. [Continue reading…]

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Jumping genes play a big role in what makes us human

Science News reports: Face-to-face, a human and a chimpanzee are easy to tell apart. The two species share a common primate ancestor, but over millions of years, their characteristics have morphed into easily distinguishable features. Chimps developed prominent brow ridges, flat noses, low-crowned heads and protruding muzzles. Human noses jut from relatively flat faces under high-domed crowns.

Those facial features diverged with the help of genetic parasites, mobile bits of genetic material that insert themselves into their hosts’ DNA. These parasites go by many names, including “jumping genes,” “transposable elements” and “transposons.” Some are relics of former viruses assimilated into a host’s genome, or genetic instruction book. Others are self-perpetuating pieces of genetic material whose origins are shrouded in the mists of time.

“Transposable elements have been with us since the beginning of evolution. Bacteria have transposable elements,” says evolutionary biologist Josefa González. She doesn’t think of transposons as foreign DNA. They are parts of our genomes — like genes.

“You cannot understand the genome without understanding what transposable elements are doing,” says González, of the Institute of Evolutionary Biology in Barcelona. She studies how jumping genes have influenced fruit fly evolution.

Genomes of most organisms are littered with the carcasses of transposons, says Cédric Feschotte, an evolutionary geneticist at the University of Utah in Salt Lake City. Fossils of the DNA parasites build up like the remains of ancient algae that formed the white cliffs of Dover. One strain of maize, the organism in which Nobel laureate Barbara McClintock first discovered transposable elements in the 1940s, is nearly 85 percent transposable elements (SN: 12/19/09, p. 9). Corn is an extreme example, but humans have plenty, too: Transposable elements make up nearly half of the human genome.

Most of the transposons in the genomes of humans and other creatures are now “dead,” meaning they are no longer able to jump. The majority are in bits and pieces scattered throughout the genome like so much confetti. Many researchers used to think these broken transposons were just genetic garbage.

Far from junk, however, jumping gene remnants have been an evolutionary treasure trove. Some of the control switches transposons once used for their own hopping have been recycled over time into useful tools that help species, including Homo sapiens, adapt to their environments or take on new characteristics. [Continue reading…]

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New study claims hominids were in North America 130,000 years ago

Ed Yong writes: In the winter of 1992, a construction crew in San Diego, California started cutting into the rocks that flanked the State 54 Highway, in a bid to widen the road. Those rocks hailed from the Pleistocene period and were rich in Ice Age fossils, so scientists from the San Diego Museum of Natural History accompanied the crew to recover whatever they unearthed. Among bits of horse, camel, dire wolf, and ground sloth, they found the remains of a single mastodon—an extinct mammoth-like animal. “And we noticed there was something different about it,” says Thomas Deméré, who was part of the team.

Based on several lines of evidence—the way the bones are broken, the way they lay, the presence of large stones that show curious patterns of wear and are out-of-place in the surrounding sediment—the team think that early humans used rocks to hammer their way into the mastodon’s bones. That wouldn’t have been contentious in itself, but the team also claims that the bones from the “Cerruti Mastodon” are 130,000 years old. That would push back the earliest archaeological evidence for humans in North America by a whopping 115,000 years.

To put that in perspective, for decades, the first American settlers were thought to be the Clovis people, who arrived 13,000 years ago. But by discovering older sites with strong evidence of human activity, archaeologists confirmed that the continent had a pre-Clovis presence that dates back 14,600 years—or perhaps even further. Genetic studies have also suggested that modern humans entered America from Asia even earlier, around 23,000 years ago. [Continue reading…]

 

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Was the first song a lullaby?

Tom Jacobs writes: Why do humans play, and listen, to music? The question has long baffled evolutionary theorists. Some suggest it had its origins in courtship rituals, while others contend it had (and has) a unique ability to bond people together to work toward a common goal.

Now, a couple of Harvard University researchers have proposed a new concept: They argue that the earliest music  —  and perhaps the prototype for everything from Bach to rap  — may just have been the songs mothers sing to their infants.

Maybe the first musical genre wasn’t the love song, but rather the lullaby.

“The evolution of music must be a complex, multi-step process, with different features developing for different reasons,” says Samuel Mehr, who co-authored the paper with psychologist Max Krasnow. “Our theory raises the possibility that infant-directed song is the starting point for all that.”

Mothers vocalize to their babies “across many, if not all, cultures,” the researches note in the journal Evolution and Human Behavior. Its ubiquity suggests this activity plays a positive role in the parent-child relationship, presumably soothing infants by proving that someone is there and paying attention to them. [Continue reading…]

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New evidence that Lucy, our most famous ancestor, had superstrong arms

The Washington Post reports: In Ethiopia, she is known as “Dinkinesh” — Amharic for “you are marvelous.” It’s an apt name for one of the most complete ancient hominid skeletons ever found, an assemblage of fossilized bones that has given scientists unprecedented insight into the history of humanity.

You probably know her as Lucy.

Discovered in 1974, wedged into a gully in Ethiopia’s Awash Valley, the delicate, diminutive skeleton is both uncannily familiar and alluringly strange. In some ways, the 3.2-million-year-old Australopithecus was a lot like us; her hips, feet and long legs were clearly made for walking. But she also had long arms and dexterous curved fingers, much like modern apes that still swing from the trees.

So, for decades scientists have wondered: Who exactly was Lucy? Was she lumbering and land-bound, like us modern humans? Or did she retain some of the ancient climbing abilities that made her ancestors — and our own — champions of the treetops?

A new study suggests she was a little of both: Though her lower limbs were adapted for bipedalism, she had exceptionally strong arm bones that allowed her to haul herself up branches, researchers reported Wednesday in the journal PLoS One. [Continue reading…]

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Meet the frail, small-brained people who first trekked out of Africa

Science magazine reports: On a promontory high above the sweeping grasslands of the Georgian steppe, a medieval church marks the spot where humans have come and gone along Silk Road trade routes for thousands of years. But 1.77 million years ago, this place was a crossroads for a different set of migrants. Among them were saber-toothed cats, Etruscan wolves, hyenas the size of lions—and early members of the human family.

Here, primitive hominins poked their tiny heads into animal dens to scavenge abandoned kills, fileting meat from the bones of mammoths and wolves with crude stone tools and eating it raw. They stalked deer as the animals drank from an ancient lake and gathered hackberries and nuts from chestnut and walnut trees lining nearby rivers. Sometimes the hominins themselves became the prey, as gnaw marks from big cats or hyenas on their fossilized limb bones now testify.

“Someone rang the dinner bell in gully one,” says geologist Reid Ferring of the University of North Texas in Denton, part of an international team analyzing the site. “Humans and carnivores were eating each other.”

This is the famous site of Dmanisi, Georgia, which offers an unparalleled glimpse into a harsh early chapter in human evolution, when primitive members of our genus Homo struggled to survive in a new land far north of their ancestors’ African home, braving winters without clothes or fire and competing with fierce carnivores for meat. The 4-hectare site has yielded closely packed, beautifully preserved fossils that are the oldest hominins known outside of Africa, including five skulls, about 50 skeletal bones, and an as-yet-unpublished pelvis unearthed 2 years ago. “There’s no other place like it,” says archaeologist Nick Toth of Indiana University in Bloomington. “It’s just this mother lode for one moment in time.”

Until the discovery of the first jawbone at Dmanisi 25 years ago, researchers thought that the first hominins to leave Africa were classic H. erectus (also known as H. ergaster in Africa). These tall, relatively large-brained ancestors of modern humans arose about 1.9 million years ago and soon afterward invented a sophisticated new tool, the hand ax. They were thought to be the first people to migrate out of Africa, making it all the way to Java, at the far end of Asia, as early as 1.6 million years ago. But as the bones and tools from Dmanisi accumulate, a different picture of the earliest migrants is emerging. [Continue reading…]

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Humans aren’t the only primates that can make sharp stone tools

 

The Guardian reports: Monkeys have been observed producing sharp stone flakes that closely resemble the earliest known tools made by our ancient relatives, proving that this ability is not uniquely human.

Previously, modifying stones to create razor-edged fragments was thought to be an activity confined to hominins, the family including early humans and their more primitive cousins. The latest observations re-write this view, showing that monkeys unintentionally produce almost identical artefacts simply by smashing stones together.

The findings put archaeologists on alert that they can no longer assume that stone flakes they discover are linked to the deliberate crafting of tools by early humans as their brains became more sophisticated.

Tomos Proffitt, an archaeologist at the University of Oxford and the study’s lead author, said: “At a very fundamental level – if you’re looking at a very simple flake – if you had a capuchin flake and a human flake they would be the same. It raises really important questions about what level of cognitive complexity is required to produce a sophisticated cutting tool.”

Unlike early humans, the flakes produced by the capuchins were the unintentional byproduct of hammering stones – an activity that the monkeys pursued decisively, but the purpose of which was not clear. Originally scientists thought the behaviour was a flamboyant display of aggression in response to an intruder, but after more extensive observations the monkeys appeared to be seeking out the quartz dust produced by smashing the rocks, possibly because it has a nutritional benefit. [Continue reading…]

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Where did the first farmers live? Looking for answers in DNA

Carl Zimmer writes: Beneath a rocky slope in central Jordan lie the remains of a 10,000-year-old village called Ain Ghazal, whose inhabitants lived in stone houses with timber roof beams, the walls and floors gleaming with white plaster.

Hundreds of people living there worshiped in circular shrines and made haunting, wide-eyed sculptures that stood three feet high. They buried their cherished dead under the floors of their houses, decapitating the bodies in order to decorate the skulls.

But as fascinating as this culture was, something else about Ain Ghazal intrigues archaeologists more: It was one of the first farming villages to have emerged after the dawn of agriculture.

Around the settlement, Ain Ghazal farmers raised barley, wheat, chickpeas and lentils. Other villagers would leave for months at a time to herd sheep and goats in the surrounding hills.

Sites like Ain Ghazal provide a glimpse of one of the most important transitions in human history: the moment that people domesticated plants and animals, settled down, and began to produce the kind of society in which most of us live today.

But for all that sites like Ain Ghazal have taught archaeologists, they are still grappling with enormous questions. Who exactly were the first farmers? How did agriculture, a cornerstone of civilization itself, spread to other parts of the world?

Some answers are now emerging from a surprising source: DNA extracted from skeletons at Ain Ghazal and other early settlements in the Near East. These findings have already challenged long-held ideas about how agriculture and domestication arose. [Continue reading…]

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Can great apes read your mind?

By Christopher Krupenye, Max Planck Institute

One of the things that defines humans most is our ability to read others’ minds – that is, to make inferences about what others are thinking. To build or maintain relationships, we offer gifts and services – not arbitrarily, but with the recipient’s desires in mind. When we communicate, we do our best to take into account what our partners already know and to provide information we know will be new and comprehensible. And sometimes we deceive others by making them believe something that is not true, or we help them by correcting such false beliefs.

All these very human behaviors rely on an ability psychologists call theory of mind: We are able to think about others’ thoughts and emotions. We form ideas about what beliefs and feelings are held in the minds of others – and recognize that they can be different from our own. Theory of mind is at the heart of everything social that makes us human. Without it, we’d have a much harder time interpreting – and probably predicting – others’ behavior.

For a long time, many researchers have believed that a major reason human beings alone exhibit unique forms of communication, cooperation and culture is that we’re the only animals to have a complete theory of mind. But is this ability really unique to humans?

In a new study published in Science, my colleagues and I tried to answer this question using a novel approach. Previous work has generally suggested that people think about others’ perspectives in very different ways than other animals do. Our new findings suggest, however, that great apes may actually be a bit more similar to us than we previously thought.

[Read more…]

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The world’s most sustainable technology

Stephen E. Nash writes: To my mind, a well-made Acheulean hand ax is one of the most beautiful and remarkable archaeological objects ever found, anywhere on the planet. I love its clean, symmetrical lines. Its strength and heft impress me, and so does its persistence.

Acheulean hand ax is the term archaeologists now use to describe the distinctive stone-tool type first discovered by John Frere at Hoxne, in Suffolk, Great Britain, in the late 1700s. Jacques Boucher de Perthes, a celebrated archaeologist, found similar objects in France during excavations conducted in the 1830s and 1840s. The name Acheulean comes from the site of Saint-Acheul, near the town of Amiens in northern France, which de Perthes excavated in 1859.

The term hand ax is arguably a misnomer. While the stone tool could conceivably have been used to chop — as with a modern ax — there is little evidence the implement was attached to a handle. In the absence of a handle, the user would have seriously damaged his or her hands while holding onto the ax’s sharp edges and striking another hard substance. There is evidence, however — in the form of telltale microscopic damage to the hand-ax edges and surfaces — that these objects were used for slicing, scraping, and some woodworking activities. Hand axes also served as sources of raw material (in strict archaeological terms, they were cores) from which new, smaller cutting tools (flakes) were struck. So they likely served a range of purposes. [Continue reading…]

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Study suggests human proclivity for violence gets modulated but is not necessarily diminished by culture

A new study (by José Maria Gómez et al) challenges Steven Pinker’s rosy picture of the state of the world. Science magazine reports: Though group-living primates are relatively violent, the rates vary. Nearly 4.5% of chimpanzee deaths are caused by another chimp, for example, whereas bonobos are responsible for only 0.68% of their compatriots’ deaths. Based on the rates of lethal violence seen in our close relatives, Gómez and his team predicted that 2% of human deaths would be caused by another human.

To see whether that was true, the researchers dove into the scientific literature documenting lethal violence among humans, from prehistory to today. They combined data from archaeological excavations, historical records, modern national statistics, and ethnographies to tally up the number of humans killed by other humans in different time periods and societies. From 50,000 years ago to 10,000 years ago, when humans lived in small groups of hunter-gatherers, the rate of killing was “statistically indistinguishable” from the predicted rate of 2%, based on archaeological evidence, Gómez and his colleagues report today in Nature.

Later, as human groups consolidated into chiefdoms and states, rates of lethal violence shot up — as high as 12% in medieval Eurasia, for example. But in the contemporary era, when industrialized states exert the rule of law, violence is lower than our evolutionary heritage would predict, hovering around 1.3% when combining statistics from across the world. That means evolution “is not a straitjacket,” Gómez says. Culture modulates our bloodthirsty tendencies.

The study is “innovative and meticulously conducted,” says Douglas Fry, an anthropologist at the University of Alabama, Birmingham. The 2% figure is significantly lower than Harvard University psychologist Steven Pinker’s much publicized estimate that 15% of deaths are due to lethal violence among hunter-gatherers. The lower figure resonates with Fry’s extensive studies of nomadic hunter-gatherers, whom he has observed to be less violent than Pinker’s work suggests. “Along with archaeology and nomadic forager research, this [study] shoots holes in the view that the human past and human nature are shockingly violent,” Fry says. [Continue reading…]

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Evidence rebuts Chomsky’s theory of language learning

Paul Ibbotson and Michael Tomasello write: The idea that we have brains hardwired with a mental template for learning grammar — famously espoused by Noam Chomsky of the Massachusetts Institute of Technology — has dominated linguistics for almost half a century. Recently, though, cognitive scientists and linguists have abandoned Chomsky’s “universal grammar” theory in droves because of new research examining many different languages—and the way young children learn to understand and speak the tongues of their communities. That work fails to support Chomsky’s assertions.

The research suggests a radically different view, in which learning of a child’s first language does not rely on an innate grammar module. Instead the new research shows that young children use various types of thinking that may not be specific to language at all — such as the ability to classify the world into categories (people or objects, for instance) and to understand the relations among things. These capabilities, coupled with a unique hu­­­man ability to grasp what others intend to communicate, allow language to happen. The new findings indicate that if researchers truly want to understand how children, and others, learn languages, they need to look outside of Chomsky’s theory for guidance.

This conclusion is important because the study of language plays a central role in diverse disciplines — from poetry to artificial intelligence to linguistics itself; misguided methods lead to questionable results. Further, language is used by humans in ways no animal can match; if you understand what language is, you comprehend a little bit more about human nature. [Continue reading…]

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The race to save a dying language

Ross Perlin writes: n 2013, at a conference on endangered languages, a retired teacher named Linda Lambrecht announced the extraordinary discovery of a previously unknown language. Lambrecht – who is Chinese-Hawaiian, 71 years old, warm but no-nonsense – called it Hawaii Sign Language, or HSL. In front of a room full of linguists, she demonstrated that its core vocabulary – words such as “mother”, “pig” and “small” – was distinct from that of other sign languages.

The linguists were immediately convinced. William O’Grady, the chair of the linguistics department at the University of Hawaii, called it “the first time in 80 years that a new language has been discovered in the United States — and maybe the last time.” But the new language found 80 years ago was in remote Alaska, whereas HSL was hiding in plain sight in Honolulu, a metropolitan area of nearly a million people. It was the kind of discovery that made the world seem larger.

The last-minute arrival of recognition and support for HSL was a powerful, almost surreal vindication for Lambrecht, whose first language is HSL. For decades, it was stigmatised or ignored; now the language has acquired an agreed-upon name, an official “language code” from the International Organization for Standardization, the attention of linguists around the world, and a three-year grant from the Endangered Languages Documentation Programme at the School of Oriental and African Studies in London.

But just as linguists were substantiating its existence, HSL stood on the brink of extinction, remembered by just a handful of signers. Unless the language made a miraculous recovery, Lambrecht feared that her announcement might turn out to be HSL’s obituary.

Three years after announcing its existence, Lambrecht is still unearthing her language sign by sign. She may be the only person in the world who still uses HSL on a regular basis, signing into a camera while a linguist named James “Woody” Woodward and a handful of graduate students from the University of Hawaii document her every move. [Continue reading…]

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