Neanderthal kids grew up faster than humans: study

Kerry Sheridan, Yahoo News – Mon Nov 15, 2010Original article here

WASHINGTON (AFP) – Facing untold pressures to survive, Neanderthal kids grew up much faster than modern human tots, whose lengthy childhoods may be a relatively new phenomenon that has helped boost longevity.

That’s according to a study by led researchers at Harvard University, the latest to highlight small but crucial differences in early development between humans and our closest cousins who became extinct about 28,000 years ago.

Researchers made the discovery after using a new “supermicroscrope” with an advanced X-ray technique to examine the teeth of previously discovered fossils of eight Neanderthal children.

“The Neanderthal children seemed to show a lot of stress,” said lead study author Tanya Smith, assistant professor of human evolutionary biology at Harvard, noting that teeth can offer plenty of clues about overall development.

“Inside and outside, the Neanderthal teeth show a lot of these developmental defects in high frequencies. It seems like childhood was tough for Neanderthals.”

The study, which appeared in the Proceedings of the National Academy of Sciences, said that young Neanderthals’ teeth growth “was significantly faster than in our own species.”

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.

During the five-year study, scientists at Harvard, the Max Planck Institute for Evolutionary Biology and the European Synchrotron Radiation Facility examined and compared the remains of Neanderthal and human children.

Using a highly developed “supermicroscope” that helped peer deeper into the dental fossils without damaging them, researchers found that the first hominin fossil ever discovered, that of a young Neanderthal girl found in Belgium, was actually about three years old when she died, not four to five as previously thought.

Scientists were even able to detect a “tiny ‘birth certificate'” inside molars that offered a precise way to calculate how old a juvenile was at death, Smith said.

“Teeth are remarkable time recorders, capturing each day of growth much like rings in trees reveal yearly progress,” she said.

Previous research has pointed to differences in how early humans and apes mature and grow.

For example, ape females have shorter pregnancies that result in offspring growing up faster and reproducing at younger ages than humans. Chimpanzees on average bear their first babies at age 13, compared to age 19 in humans.

“It doesn’t make any sense to lengthen your childhood if there is no guarantee you are going to make it to a ripe old age,” said Smith.

However, it is less clear when this evolutionary shift began to occur in the path of human development.

Smith described the change as a “costly yet advantageous shift from a primitive ‘live fast and die young’ strategy to the ‘live slow and grow old’ strategy that has helped to make us one of the most successful organisms on the planet.”

When the researchers examined tooth specimens from the earliest members of our own species, using one set of dental remains found in Morocco 160,000 years ago and one that dates back 90-100,000 years found in Israel, they found they were remarkably similar to modern humans.

“They look pretty much like us,” said Smith. “This longer period of growth and development is a condition that is unique to our own species.”

The advances in examining the age of the teeth were possible by using what the study called a “supermicroscope” that employs “extremely powerful X-ray beams” developed at the European Synchrotron Radiation Facility in Grenoble, France.The synchotron at Grenoble is the largest in the world, and has been visited by museum curators and scientists bearing rare fossils from around the world so that they can be imaged and analyzed anew, the study said.

A study released last week showed that the brains of Neanderthals, believed to be modern humans’ closest ancestor, were similar to humans’ at birth but developed differently in the first year of life.

Neanderthal and human brains similar shape at birth, research shows

By Amina Khan, Los Angeles Times
November 13, 2010
Original article here

Human brains soon become more rounded, but those of the extinct species retained an elongated shape. The findings could help scientists determine the cognitive differences between the two species.

The shape-shift of human brains may be linked to some underlying structural changes in brain regions that account for emotional, social and language development. (CSIC, EPA / May 6, 2010)

The newborn brains of Neanderthals looked remarkably similar to human brains at birth and then began to diverge drastically over the first year of life, European scientists have reported. The findings, reported online Monday in the journal Current Biology, could help paleoanthropologists figure out the cognitive differences between modern humans and their extinct relatives — and when, exactly, those differences developed.

A team led by paleoanthropologist Philipp Gunz of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, scanned the skulls of several Neanderthals, including a newborn, and mapped out the shape of the brain cavity. Gunz said he decided to look at the differences between human and Neanderthal skulls after finding in an earlier study that chimpanzee and human brains have the same elongated shape at birth, but that the human baby’s brain quickly becomes more rounded.

Gunz wondered whether even though human and Neanderthal brains were roughly the same size, they would find a similar difference in shape between young humans and Neanderthals, who went extinct about 25,000 years ago.Human and Neanderthal brains were remarkably similar in shape right after birth, the scientists found — perhaps because of the common need to squeeze a baby’s head through its mother’s birth canal.

But differences set in during the first year. Human brains begin to morph from an elongated shape to a more rounded one. The Neanderthal brains, similar to chimpanzee brains, retained their oblong shape.

Although any inference about Neanderthals’ cognitive ability would be speculative at best, Gunz said, the shape-shift of human brains may be linked to some underlying structural changes in brain regions that account for emotional, social and language development.

“We think shape indicates a difference in the speed of development,” Gunz said, “because if you grow faster or slower, the brain shape changes differently…. We know from modern humans that the way you grow your brain affects the pattern of neural wiring.”

Steven Leigh, a biological anthropologist at the University of Illinois at Urbana-Champaign, said the findings were interesting. “There obviously has been a lot of debate about the evolution of the human brain and at what points the brain differs from other species, including Neanderthals,” he said. “They seem to be getting closer to the answer in this analysis.”

What Makes Us Human? Neanderthal Genome Holds Clues

The rough draft of the Neanderthal genome is complete.

Using 38,000-year-old bone fragments and new shotgun sequencing technology, researchers have sequenced 3.7 billion base pairs of Neanderthal DNA. That’s more than the 3 billion base pairs expected in the final draft of the genome, but many of the snippets of genetic code are repeats. At this stage scientists have just 63 percent of the hominid genome completely sequenced.

Still, even with a rough draft, scientists can begin to isolate the genetic variations that are uniquely, irreducibly human.

“The first big goal of this project, which is really about understanding our evolution, is this catalog of [evolutionary] changes,” said the project leader, Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. “The second goal is finding evidence of positive selection, of where something changed in our ancestors that really made a difference in how we reproduce and survive.”

Neanderthals are our closest relatives on the hominid family tree. We split from them about 500,000 years ago and for the next 475,000 years or so, modern humans and Neanderthals coexisted on the planet and sometimes even in the same region. The relationship between humans and our cousins has inspired lots of ideas about sex and war. Recently scientists have speculated that Neanderthals and humans in Europe could have interbred, while others have speculated that humans killed off the Neanderthals.

The draft genome does not yet provide enough evidence to answer some of the big questions about the relationship between humans and our cousins, but already little details are emerging. For example, last year the team revealed that a gene known to be important in the development of speech was present in the Neanderthal genome.

“There’s no reason to think they [couldn’t] articulate as we do, although there are many more genes related to speech,” Pääbo told reporters at the AAAS annual meeting in Chicago, which runs through Monday.

We also know that Neanderthals were sophisticated toolmakers and were highly intelligent, although that remains a subject of debate.

The question becomes, then, what switch was thrown that allowed modern humans to surpass all previous hominid species and become the world-dominating predator that we are?

“Why are Neanderthals so important to us and why do we want to know about their genome? Because the Neanderthals represent the last divergent branch of the human evolutionary bush,” said Jean-Jacques
Hublin, who studies evolution at the Planck Institute. “Studying the
Neanderthal genome tells us what makes modern humans really modern and really human.”

In small ways, studying the Neanderthal genome tells us something about Neanderthals, too. For example, Pääbo revealed that Neanderthals didn’t possess a mutation often found in humans that allows us to metabolize lactose, which lets cow’s milk do a body good.

“We can start looking at interesting genes to start seeing what Neanderthals might have been like,” he said.

With the draft completed, the researchers will try to collect more
DNA and sequence it faster to get a “deeper” read on the genome, increasing its accuracy and filling in the gaps. They now have five archaeological sites from which they can recover genetic fragments, including a new excavation in Spain that is taking precautions to prevent destroying or contaminating the fragile genes.

The more complete and redundant sequencing effort will allow the scientists to isolate genes unique to the Neanderthals, not just variations on human genes. By sequencing 15 or 20 times as many base pairs as exist in the Neanderthal genome, the researchers will be able to separate mistakes from unique genes.

“We’re going to sequence things much deeper, get 15 to 20 times coverage,” Pääbo said.  “Then, we’ll be able to believe things that are

But don’t get your hopes up for creating a Neanderthal clone, a real-life Encino Man meets Jurassic Park. Researchers say that will remain technically impossible.

— Alexis Madrigal, staff writer

Original article here

Neither Neanderthal nor sapiens: new human relative IDed

By John Timmer | Last updated 3 days ago

At a press conference yesterday, researchers announced the completely unexpected: a Siberian cave has yielded evidence of an entirely unknown human relative that appears to have shared Asia with both modern humans and Neanderthals less than 50,000 years ago. The find comes courtesy of a single bone from individual’s hand. Lest you think that paleontologists are overinterpreting a tiny fragment, it wasn’t the shape of the bone that indicates the presence of a new species—it was the DNA that it contained.

The paper that describes the finding comes courtesy of the Max Planck Institute’s Svante Pääbo, who has been actively pursuing the sequencing of the Neanderthal genome. It seems likely that this particular bone fragment was targeted due to suspicions that it might also provide an additional Neanderthal sequence. The site, called Denisova, is in the Altai Mountains of southern Siberia, an area that has had hominins present as early as 125,000 years ago. The sample itself came from a layer of material that dates from between 30,000 and 50,000 years ago. Neanderthal DNA was found in a sample from the same time period less than 100km away, while artifacts indicate that modern humans were also present in the region by 40,000 years ago.

So, there was no apparent reason to suspect that the bone would yield anything more than a familiar sequence. And in fact, most of the first half of the paper simply describes the methods used to construct a complete sequence of the mitochondrial DNA, including over 150-fold coverage of the genome, and an alignment program designed to account for the errors typical of ancient DNA sequences. About the only surprise here is that Pääbo’s group has switched from using 454 sequencing machines to those made by Illumina.

Various checks indicate that the sequence the authors obtained contains damage that’s typical of ancient DNA, and that it all comes from a single individual. So far, quite typical.

Things got quite unusual when they attempted to align the sequence to the mitochondrial DNA from the hominin species that were likely to be present at that time and place: human and Neanderthal. Instead of clustering with one or the other, the Denisova mitochondrial genome was a clear outlier, having about 385 differences with the typical human mitochondrial genome. In contrast, Neanderthals only differ from modern humans by an average of 202. The obvious interpretation is that the Denisova lineage split off before modern humans and Neanderthals did. If we accept that Neanderthals are a distinct species of hominin (and we do), then this sample clearly represents yet another one.

Building a tree with the chimpanzee genomes and assuming a divergence time of 6 million years, the data indicates that the Denisova lineage diverged about a million years ago. At that point, Homo Erectus was already a global species, but our human ancestors were still in Africa. That suggests that the Denisova variant probably originated in, or at least near, Africa as well, although there’s no way to tell whether it was a distinct species before it started migrating, or whether it became an isolated population because of a migration.

The paper is in the format of a Nature letter, which allows only a paragraph for discussion. The authors use that space primarily to note that, 40,000 years ago, southern Siberia was a very busy place as far as hominins are concerned, with at least three different species present within a very narrow time frame. If we accept that the Indonesian hobbits are yet another distinct species—and the relevant community seems to be leaning that way—then it appears that there were at least four distinct hominin species cohabiting the globe in the very recent past.

As surprising as that is, it’s only a small fraction of the implications of this work. For starters, there’s the whole idea that we can identify a new species without having any idea what it actually looked like—in fact, without having any idea of whether it would be physically distinct enough from any of the other hominin species around that we’d even have known it were a separate species based on the bones.

The authors also briefly touched on a separate issue: this ability will be unevenly distributed in space and time. DNA simply lasts longer in cool climates, as evidenced by the recent announcement that DNA had been obtained from a polar bear sample that was over 100,000 years old. So, any species that was stuck near the equator—like the hobbits—are unlikely to be in on the DNA revolution. This is especially unfortunate given the fact that, as noted above, a lot of the most interesting action in hominin origins seem to have been taking place in Africa.

Then there’s the whole question of what else we might be missing. Avoiding contamination issues with modern DNA is easiest if the entire excavation is designed around a sterile technique from the start, meaning bones that have been previously excavated aren’t ideal. At the moment, at least, sequencing from a single sample is also pretty labor intensive (this paper had seven authors), meaning we aren’t likely to be able to just start sequencing any bone fragments we stumble across. Figuring out how to prioritize what might be informative will be a real challenge.

If that seems like a lot of questions for a short and fairly technical paper (and it is), it’s a product of the fact that this paper seems truly exceptional. Because of the rich history of most fields of science, there aren’t a whole lot of truly unexpected results, since you typically know that there are people working in a given area. But this finding is truly a stunning one, and really seems to be a complete surprise.

Nature, 2010.

Original article here.