When I was 9 years old I desperately wanted to be a paleontologist, but sadly, daydreams of unearthing dinosaurs led to no significant fossil finds in my backyard. So I must confess unending respect for Matthew Berger, who, at age 9, quite by accident made a stunning scientific find. In the journal Science this week, Matthew’s father paleoanthropologist Lee Berger describes the fossils of a brand-new hominid species that they turned up in South Africa: Australopithecus sediba, which dates back to between 1.78 and 1.95 million years and could offer new hints about that era of human evolution.
Matthew was chasing his dog near a site where his father had long hunted for fossils when he tripped over the find. The bones belong to a pre-teenage boy and a woman estimated to be in her late 20s or early 30s; the individuals died at about the same time, and before their remains had fully decomposed, they were entombed in an avalanche of sediment and nearly perfectly preserved deep in the Malapa cave north of Johannesburg, South Africa [TIME]. As a result, Lee Berger says, the bones are in an astonishing state for their nearly 2-million-year age.
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In 2008, archeologists working at the Denisova Cave in Siberia’s Altai Mountains discovered a tiny piece of a finger bone, believed to be a pinky, buried with ornaments in the cave. Scientists extracted the mitochondrial DNA (genetic material from the mother’s side) from the ancient bone and checked to see if its genetic code matched with the other two known forms of early hominids–Neanderthals and the ancestors of modern humans. What they found was a real surprise. The team, led by geneticist Svaante Paabo of the Max Planck Institute, discovered that the mtDNA from the finger bone matched neither–suggesting there might have been an entirely different hominid species that roamed the planet about 50,000 years ago.
Looking back at the region and the cave, where scientists earlier discovered artifacts from humans and Neanderthals, Paabo thinks that it is possible that all the three species (modern humans, Neanderthals and the mystery hominids) could have possibly met and interacted with each other. The findings, which were published in journal Nature, present an unexpected twist in the story of human evolution and migration.
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For years, scientists have debated where humanity’s sense of fairness came from. Some proposed it was a glitch in the brain’s wiring that causes people to be kind and fair to strangers, while others said it was a remnant of Stone Age thinking--that deep in our brains we see everyone we meet as part of our tiny family, and can’t imagine encountering someone who won’t ever be seen again [Wired]. But now, in a new study published in Science, scientists studying groups of people from different societies have suggested that our sense of fairness may depend on the type of society we live in.
The researchers found evidence that the more complex the society, the more developed those people’s sense of fairness. You can’t get the effects we’re seeing from genes,” said Joe Henrich, a University of British Columbia evolutionary psychologist and co-author of the study.” These are things you learn as a consequence of growing up in a particular place” [Wired].
For this study, scientists observed 2,100 people from different societies–from African herders, Colombian fishermen, and Missouri wage workers. The groups varied in size, and researchers also evaluated the people’s involvement in organized social activities like markets and religion–a common marker, scientists say, of the presence of a moral code that extends beyond kin. They then administered a series of games to study how group members viewed selfish behavior and how willing they were to punish it.
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With the genetics age coming into its own, the number of people who have had their genome sequenced could soon explode. But the genetic sequencing done so far has mostly left out African people, genetics researcher Stephan Schuster says. So he led a team that sequenced the genome of five people native to southern Africa—including famed anti-apartheid activist Archbishop Desmond Tutu—and found incredible genetic diversity compared to people in other parts of the world. The findings are in the journal Nature.
The genome of the archbishop, who is 79, was particularly important for the study because he is a Bantu descended from the Tswana and Nguni people, who account for around 80% of southern Africans [The Guardian]. The other four subjects were bushmen: One, named !Gubi, had his entire genome sequenced, while the other three were partially sequenced. (The exclamation point indicates a clicking sound in that Bushman language.) !Gubi is the first person from an African minority population to be fully sequenced, and comparing him to the other three men from the region shows as much genetic separation as you’d expect to find between European and Asian peoples. Says Schuster: “This is despite the fact that they sometimes live within walking distance of one another” [Nature News].
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Don’t count out the Y chromosome just yet. Far from being in a state of decay, as some studies have suggested, a new study in Nature says the male chromosome in humans is actually evolving at a furious pace.
Study leader David Page of MIT sequenced the human Y chromosome back in 2003, and in the new study his team compares it to the male chromosome of chimpanzees. The scientists expected the two sequences to look very similar. However, while human and chimp DNA generally differ by less than 2 per cent, more than 30 per cent of the Y chromosome differed between the two species [The Times].
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The jewelry in Spain speaks mainly to the brains (of Neanderthals). So says a team of archaeologists this week in the Proceedings of the National Academy of Sciences. Researchers led by João Zilhão have turned up artifacts they believe to be jewelry dating back 50,000 years—a time only Neanderthals and not early humans occupied Europe—suggesting to them that those Neanderthals were capable of the abstract thinking necessary to make symbolic art.
Zilhão’s team found shells and bones that showed evidence of craftsmanship, the scientists say. First, some of the shells were perforated and could have been strung and worn as a necklace. It’s not out of the question that those holes could be natural, but the team says the finds also appear to have been painted. If the researchers’ analysis is correct, the Neanderthals could have mixed up reddish goethite and hematite, yellow siderite and natrojarosite, black charcoal and sparkly pyrite to create a spectrum of paints [MSNBC].
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Surprise, surprise. An independent analysis of the primate fossil that was unveiled amid extraordinary hype last May has found significant evidence that the lemur-like creature was not a direct ancestor of humans, after all. The 47-million-year old fossil described in May, which was given the scientific name Darwinius masillae and nicknamed Ida, was announced with unrestrained razzmatazz. She was the “eighth wonder of the world”, “our Mona Lisa” and an evolutionary “Rosetta Stone”, according to the researchers who unveiled her…. She was, they said, the “link” between us and the rest of the animal kingdom [The Guardian].
But Ida, who was the subject of both a book and a TV special that were released at the same time as the scientific paper describing the fossil, failed to wow many evolutionary biologists. Says Erik Seiffert, lead researcher of the new study: ”The suggestion that Ida [was]… specifically related to the higher primates, namely monkeys, apes and humans, was actually a minority view from the start. So it came as a surprise to many of us who are studying primate palaeontology” [BBC News].
Seiffert’s new analysis began with his attempt to identify another fossil primate, Afradapis longicristatus, which he found to be a close relation to Darwinius. The researchers then compared 360 specific anatomical features of 117 living and extinct primate species to draw up a family tree [AP]. The analysis showed that both primates are located on an early twig of the branch that produced lemurs, and far from the lineage that spawned monkeys and great apes [Wired.com]. What’s more, the researchers say that both species have no modern descendants.
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Look into the future and see the women of tomorrow! A new study predicts that future women will be a tad shorter, heavier, and more fertile—that is, if the women who are currently most successful at producing children are any indication. The team studied 2238 women who had passed menopause and so completed their reproductive lives…[and] tested whether a woman’s height, weight, blood pressure, cholesterol or other traits correlated with the number of children she had borne. They controlled for changes due to social and cultural factors to calculate how strongly natural selection is shaping these traits [New Scientist].
Their results show that shorter, heavier women tend to have more children, as do women with lower blood pressure and cholesterol. If the mothers pass on these traits for 10 generations, the average woman in 2409 will be 2 centimetres shorter and 1 kilogram [about 2 pounds] heavier than she is today. She will bear her first child about 5 months earlier and enter menopause 10 months later [New Scientist]. A two-centimeter decrease over 400 years may be a modest change, but the researchers say it’s evolution in action. The study will be published in Proceedings of the National Academy of Sciences.
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Humans typically feel uneasy when they see a very realistic human-looking robot or computer avatar, a phenomenon called the “uncanny valley” response. According to a new study performed with monkeys, that reaction might have an evolutionary basis.
Researchers hypothesize that the response stems from almost realistic images that signal HUMAN! to us, but then fail to live up to the initial excitement. The uncanny valley response has been documented in humans since the 1970s, and has been blamed for the unpopularity of some CGI films with realistic characters [like The Polar Express and Final Fantasy], and it is touted as the reason Pixar stuck to characters with cartoonish features [New Scientist].
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The tender interactions between human mothers and their newborn babies may have deep evolutionary roots: a new study found that rhesus macaque monkey mothers engage in strikingly similar behavior with their infants.
The researchers found that the mothers would gaze intently at their newborns, sometimes even taking their baby’s face with their hands and gently pulling it towards them to get an even closer look. They would also engage in “lipsmacking” – an affectionate form of expression, where the macaques rapidly open and close their mouths [BBC News]. Several videos taken by the researchers show that just like human babies, the infant monkeys responded to their mothers by mimicking their facial expressions and returning their stares.
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Humanity has a new matriarch: a hominid named Ardi who lived in Ethiopia 4.4 million years ago. Anthropologists have unveiled the results of 17 years of research on a new species named Ardipithecus ramidus, presenting a rich trove of fossils including the partial skeleton of the small-brained, 110-pound female. Ardi is 1.2 million years older than the famed “Lucy,” of the species Australopithecus afarensis, and experts say the find fundamentally changes our understanding of human evolution.
Study coauthor Tim White says that Ardi provides clues to what the last common ancestor shared by humans and chimps might have looked like before their lineages diverged about 7 million years ago…. But despite being “so close to the split,” says White, the surprising thing is that she bears little resemblance to chimpanzees, our closest living primate relatives [Time].
Ardi’s pelvis, leg, and feet bones indicated that she walked upright on two feet, but her opposable big toes suggest that she was also comfortable climbing trees. Her hand, arm, and shoulder bones indicate that she didn’t often swing through the trees, though; instead she probably walked on her palms along tree branches like some extinct apes. Based on Ardi’s anatomy, it appears that chimpanzees may actually have evolved more than humans — in the scientific sense of having changed more over the past 7 million years or so [Time].
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Stone Age Europeans may not have been the last to hear about those nifty gadgets called stone axes, after all. New research at two sites in southern Spain indicates that the people there were fashioning hand axes as early as 900,000 years ago, far earlier than previously believed.
Hand axes have sometimes been called the Swiss Army knives of the Stone Age world. They vary in shape and size, but most are at least roughly symmetrical, with one pointed and one rounded edge. Hand axes were very handy for butchering animals and cutting the stalks of tough plants [ScienceNOW Daily News]. Previously, archaeologists believed that the first Europeans lagged behind people living in Africa, the Middle East, and Asia in their tool-making capabilities. Axes dating back to 1.5 million years ago have been found in Africa, while the earliest axes found in Europe were thought to be no more than 500,000 years old.
The new study, published in Nature, suggests that vital information about tool-making traveled relatively quickly through the ancient world. The new time frame was determined through a process called paleomagnetic dating, which takes advantage of the fact that the Earth’s magnetic field has reversed itself often on geological timescales. By analyzing the polarity of magnetic minerals in rock, scientists can determine when the rock formed…. At each site, the researchers took samples at regular intervals above and below the level where hand axes were found. The last complete magnetic reversal was 780,000 years ago, and both sites dated back to about this time [The New York Times]. At the two sites, the analyses indicated that the tools were at least 760,000 and 900,000 years old, respectively.
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Image: Michael Walker
Imitation may be the sincerest form of flattery not just for humans, but for many primates. In human social interactions, people have an instinctive tendency to copy each other’s body language and mannerisms, and previous studies have shown that such imitation gives rise to friendly feelings. Now a new study has found that capuchin monkeys respond to imitation in the same way, suggesting that the behavior may date back to early in our evolutionary history. The subtle aping may promote the formation of social groups—building cooperation, reducing conflict, and aiding the survival of each individual [Scientific American].
To study the behavior in capuchin monkeys, which live in highly social groups of 30 or 40 individuals, the researchers gave each monkey a Wiffle ball — a lightweight plastic ball with holes in it. Monkeys typically poked the ball with their fingers, put it in their mouths or used it to pound on something. Each monkey was paired up with two human researchers, one that copied their ball-handling skills, and one that did not. When the balls were put away, the monkeys appeared to prefer the company of the like-minded ball handler [Reuters].
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A Stone Age campsite on the coast of South Africa has revealed the earliest evidence of early humans who used fire to make better, sharper stone tools. Researchers had been surprised to find spear points and other stone implements made of silcrete, a crumbly rock that doesn’t respond well to the flaking, chipping process that early tool-makers employed. But lead researcher Kyle Brown noticed that many of the ancient blades bore the same glossy sheen as North American tools created from heat-treated stone. “It seemed like the most logical thing to do was take some of this poor quality material that we’ve been collecting and put it under a fire and see what happens,” he says [New Scientist].
Brown buried silcrete stones in a fire pit and kept a roaring fire going for up to 10 hours at a time. When the blaze eventually died down and the rocks had cooled, they looked different, with a new reddish sheen. They also had different physical properties. “The stone becomes harder and stiffer,” Brown says. “It basically becomes more brittle, which is great if you are breaking something [and] you want it to break more easily” [NPR News]. The flakes from the treated stones were also sharper than those created from untreated silcrete.
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Analysis of a Neanderthal skeleton known as Shanidar 3 found in the late 1950s shows that the he likely died from injuries incurred by a thrown spear, which scientists speculate was thrown by a modern human, according to a study published in the Journal of Human Evolution.
Although a nicked rib on his left side provided a hint as to what killed Shanidar 3, scientists remained stumped on the details for decades. To find a probable cause of death for the Neanderthal, the researchers used a specially-designed crossbow to fire stone-age projectiles at precise velocities at pig carcasses…. At kinetic energies consistent with a thrown spear, the pig’s rib bore damage consistent with Shanidar 3′s isolated rib puncture [Time]. Higher kinetic energies that matched a knife or spear thrust produced more massive rib damage than that sustained by Shanidar. The scientists also found that the weapon entered Shanidar’s body from about 45 degrees above his body, provided the 5-foot-6-inch Neanderthal was standing at the time.
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