Neanderthals, it would appear, grew up in a big hurry. In a new study in the Proceedings of the National Academy of Sciences this week, Harvard anthropologists who studied Neanderthal teeth samples say that the evidence captured in those teeth show the rate at which they developed. Compared with human children, Neanderthal kids raced though their developing years and into adulthood, the researchers say.
Tanya Smith and colleagues used advanced X-ray scans of the tooth fossils of Neanderthals and the humans who lived concurrently with them to discover the layers therein. She says such scans reveal “growth lines” that serve the same purpose as tree rings–they allow researchers to measure the individual’s development year by year, and to determine his or her exact age at death.
Even when compared to some of the earliest human teeth, taken from remains of humans who left Africa 90,000 to 100,00 years ago, the differences were clear. Human teeth grew more slowly, pointing to more leisurely periods of youth. “This indicates that the elongation of childhood has been a relatively recent development,” the study said. [AFP]
When you were born, your brain was more elongated than it is now; it rounded out into its more globular shape as you grew up and crammed it full of knowledge. Neanderthals, it appears, were born with brains in that same elongated shape. But in their case it never changed: Adult Neanderthals’ brains didn’t move to the more rounded shape like ours, according to a study now out in Current Biology.
Scientists have long known that Neanderthals had brains that were about as big as our own, but this study may help explain how their cognitive abilities differed.
[The researchers used CT scans] to study nine fossil Neandertals, including a newborn, a year—old baby, and three children. Because the brain does not fossilize, they studied endocasts, imprints of the brain left in the skull. They found that at birth, both Neandertal and modern human infants had elongated braincases that were similar in shape, although Neandertal faces were already larger. But by age 1 or so, modern humans had grown globular brains, whereas Neandertal babies had not. [ScienceNOW]
Neanderthals, in keeping the same basic brain shape throughout life, maintain the pattern of brain development seen in chimpanzees. In contrast, modern humans have evolved a unique pattern, says lead researcher Philipp Gunz:
According to one group of scientists, figuring out the answer required only a pair of high-tech gloves and a trained craftsman who could make both simple stone knives and more complicated hand axes. The craftsman wore gloves studded with electronic sensors that tracked his his hand movements. Lead researcher Aldo Faisal of Imperial College London found that simple and complex tools required the same amount of dexterity to produce.
“From these results, dexterity can be ruled out, and we can infer it has something to do with the complexity of the task,” says Faisal. Axes are made in several stages, which requires switching between tasks, suggesting that a higher level of complexity is required in the brain. [New Scientist]
A bountiful archaeological site in South Africa has given up another discovery showing humans becoming sophisticated tool users. According to a study out in the journal Science, 75,000-year-old artifacts in the Blombos Cave appear to show signs of pressure flaking, a process of finely shaping hard material. Before this, study author Paola Villa says, the oldest evidence of humans using the technique was dated to just 20,000 years ago.
Pressure flaking consists of trimming the edges of a finished tool by pressing with a bone point hard enough to remove thin slices of rock. This process creates the narrow, evenly spaced grooves found on flint tools from Europe’s 20,000-year-old Solutrean culture and prehistoric Native American groups. Wider, more irregular grooves characterize 36 pressure-flaked Blombos tools, which were made from silcrete, Villa says. This rock, a silica-rich material, is of lower quality than flint and requires heating to ready it for pressure flaking. [Science News]
It’s not easy to tell from these artifacts whether their makers simply hammered them into shape or used the more sophisticated flaking method to polish them off. So the team, led by Vincent Mourre, found silcrete around the cave site and tried to make their own.
Over the past few years, studies have chipped away at the old-fashioned stereotype of dense and dumb Neanderthals. Archaeological excavations suggested the hominids made tools and weapons, fashioned jewelry, or possessed other mental faculties some presumed only early humans to have.
The Neanderthal renaissance may be in danger. For a study in the Proceedings of the National Academy of Sciences this week, radiocarbon dating expert Thomas Higham tested one of the most important Neanderthal sites in the world—Grotte du Renne in France—and found that all is not well in dating the artifacts that some archaeologists have connected to Neanderthals.
The key finding is that as you dig down through the layers of sediment in the Grotte du Renne, the age of the remains does not increase as you would expect. Instead, the ages of the different objects are all over the place, suggesting that remains from different eras have got mixed up together. [New Scientist]
It’s what happens to your brain after you’re born that makes you human.
Jason Hill and colleagues were comparing the structure of newborn brains to those of adults when they came upon a striking find, documented this week in the Proceedings of the National Academy of Sciences. Clearly, the brain expands greatly as you grow from baby to adult. But the researchers discovered not only that the brain grows in a non-uniform way, but also that the parts of the brain that change most rapidly as people grow up are the same parts that changed the most as humans evolved away from our primate relatives.
The research revealed that brain regions involved in higher cognitive and executive processes—such as language and reasoning—grow about twice as much as regions associated with basic senses such vision and hearing…. “The parts of the [brain] that have grown the most to make us uniquely humans are the same regions that tend to grow the most postnatally,” Hill said [National Geographic].
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].
When it comes to understanding fire, chimpanzees might have a leg up not only on the rest of the animal kingdom, but also on those of us in the human species who would sprint in the other direction at the sight of a blaze. A study published in the American Journal of Physical Anthropology argues that these primates don’t panic when the flames start, and could even understand the basics about how fire behaves.
Primatologist Jill Pruetz has been observing chimps in Senegal since 2001, but it was in 2006 that she first noticed how the animals reacted to wildfire. When people in the area set fires to clear the land, the chimps refused to tuck tail and run. “It was the end of the dry season, so the fires burn so hot and burn up trees really fast, and they were so calm about it,” Pruetz said of the chimps. “They were a lot better than I was, that’s for sure” [LiveScience].
Birds, whales, monkeys, and other animals constantly demonstrate simple communication through a variety of sounds. But one thing that has always separated them from humans, scientists thought, is that they haven’t achieved syntax—stringing together multiple different sounds to create another meaning, or what we might think of as a sentence. Now, in a study published in yesterday’s Proceedings of the National Academy of Sciences, researchers argue that they have observed monkeys using these rudimentary rules of grammar.
Klaus Zuberbühler and his team previously established the meanings of specific calls among the Campbell’s monkeys in the Tai National Park of the Ivory Coast, like the sound they dubbed “krak,” which by itself means a leopard approaches. This time, however, they documented call combinations. The monkeys can vary the call by adding the suffix “-oo”: “krak-oo” seems to be a general word for predator, but one given in a special context — when monkeys hear but do not see a predator, or when they hear the alarm calls of another species known as the Diana monkey [The New York Times].
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