Posts Tagged ‘ancient man’

Solving the Mysteries of Short-Legged Neandertals (Science Daily)

November 9, 2011

ScienceDaily (Oct. 19, 2011) — Original article here
While most studies have concluded that a cold climate led to the short lower legs typical of Neandertals, researchers at Johns Hopkins have found that lower leg lengths shorter than the typical modern human’s let them move more efficiently over the mountainous terrain where they lived. The findings reveal a broader trend relating shorter lower leg length to mountainous environments that may help explain the limb proportions of many different animals.

Sheep. The researchers decided to study different types of bovids -- a group of mammals including gazelles, antelopes, goats and sheep -- since these animals live in warm and cold environments on both flat and hilly terrain. (Credit: © rparys / Fotolia)

Their research was published online in the American Journal of Physical Anthropology and will appear in print in the November issue.

“Studies looking at limb length have always concluded that a shorter limb, including in Neandertals, leads to less efficiency of movement, because they had to take more steps to go a given distance,” says lead author Ryan Higgins, graduate student in the Johns Hopkins Center of Functional Anatomy and Evolution. “But the other studies only looked at flat land. Our study suggests that the Neandertals’ steps were not less efficient than modern humans in the sloped, mountainous environment where they lived.”

Neandertals, who lived from 40,000 to 200,000 years ago in Europe and Western Asia, mostly during very cold periods, had a smaller stature and shorter lower leg lengths than modern humans. Because mammals in cold areas tend to be more compact, with a smaller surface area, scientists have normally concluded that it was the region’s temperature that led to their truncated limbs compared to those of modern humans, who lived in a warmer environment overall.

However, Higgins’ group adds a twist to this story. Using a mathematical model relating leg proportions to angle of ascent on hills, he has calculated that Neandertals on a sloped terrain would have held an advantage while moving compared to their long-legged cousins, the modern humans. Because the area Neandertals inhabited was more mountainous than where modern humans tended to live, the researchers say that this assessment paints a more accurate picture of the Neandertals’ efficiency of movement as compared to humans. “Their short lower leg lengths actually made the Neandertals more adept at walking on hills,” explains Higgins.

But the group didn’t stop there. “In our field, if you want to prove an adaptation to the environment, like mountains leading to shorter leg lengths, you can’t just look at one species; you have to look at many species in the same situation, and see the same pattern happening over and over again,” says Higgins. “We needed to look at other animals with similar leg construction that existed in both flat and mountainous areas, as Neandertals and humans did, to see if animals tended to have shorter lower leg length in the mountains.”

The researchers decided to study different types of bovids–a group of mammals including gazelles, antelopes, goats and sheep–since these animals live in warm and cold environments on both flat and hilly terrain. The group took data from the literature on bovid leg bones and found that they fit the pattern: mountainous bovids, such as sheep and mountain goats, overall had shorter lower leg bones than their relatives on flat land, such as antelopes and gazelles, even when they lived in the same climates.

Investigating closely related bovids brought this trend into even sharper relief. Most gazelles live on flat land, and the one mountainous gazelle species examined had relatively shorter lower legs, despite sharing the same climate. Also, among caprids (goats and sheep), which mostly live on mountains, the one flat land member of the group exhibited relatively longer lower legs than all the others.

“Biologists have Bergman’s and Allen’s Rules, which predict reduced surface area to body size and shorter limbs in colder environments,” says Higgins. “Our evidence suggests that we can also predict certain limb configurations based on topography. We believe adding the topic of terrain to ongoing discussions about limb proportions will allows us to better refine our understanding of how living species adapt to their environments. This improved understanding will help us better interpret the characteristics of many fossil species, not just Neandertals.”

Funding for this research was provided by the Johns Hopkins Center of Functional Anatomy and Evolution.

This study was completed by Ryan Higgins and Christopher B. Ruff, Ph.D., also of the Johns Hopkins Center of Functional Anatomy and Evolution.

Island tool finds show early american settlers’ diversity

March 9, 2011
California Channel Island finds (J Erlandson)
The barbed points may even have been arrowheads, which would move the earliest known use of arrows back by thousands of years

Caches of tools and animal remains from around 12,000 years ago, found on islands off the California coast, have given remarkable insight into the lives of the first Americans.

The finds show fine tool technology and a rich maritime economy existed there.

The tools vary markedly from mainland cultures of the era such as the Clovis.

The finds, reported in Science, also suggest that rather than a land route to South America, early humans may have used coastal routes.

A team studying California’s Channel Islands, off its southern coast, has found that the islands show evidence both of differing technologies and a differing diet, even among the few islands.

“On San Miguel island we found a lot of pretty remarkable tools, but the animal materials there were largely shellfish,” said Torben Rick, an anthropologist from the Smithsonian Institution in Washington DC.

“Over on Santa Rosa, that site was dominated by bird remains and a few sea mammal and fish remains… and no shellfish at all.

“What’s interesting about that is it shows us not only were these people out there living a coastal life, but they were taking advantage of the full suite of resources available to them; they had a very diversified maritime economy.”

“As more research produces more sites, we will see that the story of the first Americans is not linear and that there will continue to be more surprises” -Tom Dillehay, Vanderbilt University.

The tools that the team found hold the greatest surprise, however, in that they differ significantly from those of mainland cultures like the Clovis and Folsom.

Points found on the islands – which could even be arrow-heads – are thin, serrated, and have barbed points that show striking workmanship for the period.

Inland tools had fluted points, and it is known they were used to hunt large animals including the woolly mammoth. The island points were so delicate as to almost certainly have been used for hunting fish. What is more, many of them do not reappear in the archaeological record.

“These are extremely delicate, finely made tools that don’t occur later in time,” Dr Rick said. “Finding these types of tools at all three of these sites really suggests a similar group of people, in terms of technology and subsistence – and were pretty different from what came later.”

Dr Rick said that the evidence supported the idea that the islands were short-term or seasonal encampments, rather than permanent settlements. The team also found a piece of obsidian on the islands.

“The Coso obsidian source [is] on the mainland a couple hundred miles away, so we know they were participating in long-distance exchange networks,” he said.

‘More surprises’

A long-standing model of human exploration and settlement of the Americas holds that, after reaching North America through the Bering Straits off Alaska, a concerted push southward led early humans including the Clovis culture across inland parts of the continent to South America.

But anthropologist Tom Dillehay of Vanderbilt University said that the Channel Island finds were part of a mounting body of evidence against that simplistic story.

Chert crescent from California Channel Islands (U Oregon)
The thin, serrated crescents are a testament to the island inhabitants’ manufacturing capabilities

“What they tell us is that there was widespread cultural diversity at the outset of human entry and dispersion throughout the Americas, and that the old, now-dead Clovis first model often misleads us to believe that there was only one major way of first human expansion throughout the Western Hemisphere,” he told BBC News.

“As today, there are cultural continuities but there also is constant change, which is well evidenced by these and other sites being discovered throughout the Americas. As more research produces more sites, we will see that the story of the first Americans is not linear and that there will continue to be more surprises.

“As I have published and said before, there were probably many different migrations and many different migration routes overland and along the coastal ways, and this evidence is pointing in that direction too.”

However, Dr Rick said that it was too early to upend the larger picture of human migration across the Americas, and that further finds – some of which now lie underwater around the Channel Islands – could shed more light on the story in the future.

“My colleague Jon Erlandson refers to them as ‘postcards from the past’,” Dr Rick said. “They give us just a brief snapshot of ‘hey, we were here and here’s what we were doing for a brief period of time’.

“We have to be a little cautious in our interpretations; we’re trying to put together a puzzle, and the puzzle may have 150 pieces and we’ve got five of them. So it’s really difficult to get the full picture of what they were doing.”

Neanderthal life spans similar to modern humans

January 12, 2011
By Charles Q. Choi, msnbc.com 1/11/2011
Original article here

Those who investigate Neanderthal remains have long known of a puzzling gap — elderly individuals are rare. Scientists have thus suggested that these prehistoric humans might have had an inherently shorter life expectancy than us modern humans, with our lineage ultimately outnumbering theirs, and so contributing to their demise.

Not so, according to a new study. Our once closest living relatives likely had similar life spans as us.

Our species, Homo sapiens , is the only surviving lineage of the genus Homo. Still, there once were many others, all of whom could also be called human.

Anthropologist Erik Trinkaus at Washington University in St. Louis analyzed fossil records to gauge the adult life spans of Neanderthals and early modern humans, which coexisted in different regions for about 150,000 years. He found roughly the same number of 20- to 40-year-old adults and adults older than 40 in both Neanderthal and early modern human populations, suggesting life expectancy was probably the same for both.

“Arguments for longer survival among early modern humans causing the demise of the Neandertals have no basis in fact,” Trinkaus told LiveScience. (Neanderthals are also called Neandertals due to changes in the German spelling over the years.)

Trinkaus did caution that a number of factors might skew his life-expectancy calculations. For instance, all these archaic and modern humans apparently had very mobile lifestyles during the Pleistocene to search for their next meals. That likely means any older members who could not keep up were left behind to die, and their remains would have been scattered by scavengers and lost from the fossil record.

Still, “new fossil discoveries could change the pattern some, but it is unlikely to alter it very much,” Trinkaus said. Overall, he contends that longevity did not factor into the extinction of Neanderthals. If early modern humans did have a population advantage, he argued, it was probably more due to high fertility rates and lower infant mortality.

Trinkaus detailed his findings online Jan. 10 in the Proceedings of the National Academy of Sciences.

Cretan Tools Point To 130,000-Year-Old Sea Travel

January 7, 2011

by The Associated Press/via NPR, original article here

2_Greece_Ancient_Seafarers.sff.jpg
ATHENS, Greece January 3, 2011, 04:10 pm ET

Archaeologists on the island of Crete have discovered what may be evidence of one of the world’s first sea voyages by human ancestors, the Greek Culture Ministry said Monday. A ministry statement said experts from Greece and the U.S. have found rough axes and other tools thought to be between 130,000 and 700,000 years old close to shelters on the island’s south coast.

Crete has been separated from the mainland for about five million years, so whoever made the tools must have traveled there by sea (a distance of at least 40 miles). That would upset the current view that human ancestors migrated to Europe from Africa by land alone.

“The results of the survey not only provide evidence of sea voyages in the Mediterranean tens of thousands of years earlier than we were aware of so far, but also change our understanding of early hominids’ cognitive abilities,” the ministry statement said.

The previous earliest evidence of open-sea travel in Greece dates back 11,000 years (worldwide, about 60,000 years — although considerably earlier dates have been proposed).

1_Greece_Ancient_Seafarers.sff.jpg

The tools were found during a survey of caves and rock shelters near the village of Plakias by archaeologists from the American School of Classical Studies at Athens and the Culture Ministry.

Such rough stone implements are associated with Heidelberg Man and Homo Erectus, extinct precursors of the modern human race, which evolved from Africa about 200,000 years ago.

“Up to now we had no proof of Early Stone Age presence on Crete,” said senior ministry archaeologist Maria Vlazaki, who was not involved in the survey. She said it was unclear where the hominids had sailed from, or whether the settlements were permanent.

1_Greece_Ancient_Seafarers.sff.jpg

“They may have come from Africa or from the east,” she said. “Future study should help.”

The team of archaeologists has applied for permission to conduct a more thorough excavation of the area, which Greek authorities are expected to approve later this year.

Fossil Antelope Teeth Hold Clues to Europe’s Missing Apes

August 12, 2010

Wear patterns on ancient antelope teeth have allowed researchers to reconstruct Europe’s environment 8 million years ago, when the continent’s great apes vanished.

One of those ape species could have given rise to the human lineage, making the circumstances of their disappearance especially interesting.

“Some kind of homogeneity happened around that time,” said anthropologist Gildas Merceron of France’s University Claude Bernard Lyon, co-author of a study published June 2 in the Proceedings of the Royal Society B. “We suspect a uniform environment may be linked to the decrease in great ape biodiversity.”

That apes lived in Europe seems strange today, but the continent 20 million years was warm and wet, well-suited for primates that left Africa after shrinking seas exposed a land bridge between the continents. Within a few million years, Europe hosted more than 100 species of primates, and at least 10 species of great apes.

Climate change ended that geological age. The southern icecap grew, and the Antarctic circumpolar current formed. The Asian monsoon cycle started and Europe cooled. Merceron’s study gives local detail to that big picture.

The researchers analyzed hundreds of deer and antelope teeth found at sites in Germany, Hungary and Greece and dated them to the reign of Europe’s primates and to their extinction. Wear patterns told them what sort of vegetation had prevailed. In Western and Central Europe, ruminants switched from browsing bushes and trees to grazing grasses. In Eastern Europe, the opposite happened, as grazers started to browse.

This slide into woodland homogeneity likely left the apes unable to find food, and perhaps exposed them to predators, suspects Merceron’s team. But some researchers think Europe’s apes didn’t necessarily go extinct. Some may have returned to Africa, and followed an evolutionary course ending in the modern great apes, including Homo sapiens.

“For every aspect that makes us human, there is a time and set of conditions that explains that,” said Rutgers University anthropologist Rob Scott, who was not involved in the study. “This will help explain the sort of conditions that are relevant to the earliest hominids.”

The back-into-Africa hypothesis is controversial, and contradicts the standard narrative of an all-Africa origin for the human lineage. However, there’s a gap in Africa’s great ape fossil record between 14 and 7 million years ago. The Eurasian fossil record is rich at that time.

Among the candidates for an ancestor of humans and other modern great apes are Rudapithecus hungaricus, Anoiapithecus brevirostris and Ouranopithecus macedoniensis. Especially in the face, each has features hinting at those found in known human ancestors. The last of these apes to survive was Ouranopithecus, which lived in Greece and was well-suited to eating nuts and tubers. According to Scott, it’s possible that Ouranopithecus had started to come down from the trees, developing methods of locomotion that eventually turned into bipedalism. “I’d be terribly surprised if they were totally arboreal,” he said.

All this is speculation, but even if Eurasian apes didn’t give rise to humanity, the study embodies an approach that can be applied to African apes, said Scott.

“The field is progressing from the discovery of new taxa, new names to put in our charts, to having enough information to construct larger hypotheses and scenarios,” Scott said. “We want to know, why are we human?”

Image: Artist’s rendering and fossil fragments of Anoiapithecus brevirostris./Institute of Catalan Paleontology, Autonous University of Barcelona.


Original article here.

Neanderthal man had giant arms and a body brimming with steroids, new research suggests

July 11, 2010

Neanderthal guys were no girlie-men.

Prehistoric man apparently boasted a rock-hard body, including an overdeveloped right arm that would make Popeye jealous, according to a new scientific report.

The Neanderthals hunted in the “extreme,” Russian Prof. Maria Mednikova told Discovery News. She said instead of shooting prey with a bow and arrow, the Neanderthal man used “direct contact” with his victim, stabbing animals with a spear and giving his dominant arm, usually the right one, an intense workout. The professor said female Neanderthals were strong, but more evenly muscular in both arms.

Either way, Neanderthals make modern-day humans look wimpy. Of course, they had some chemical help, it seems. Mednikova says their strong, thick bone structure was aided by a “markedly androgenic constitution.” Simply put, the Neanderthal body was brimming with natural steroids.

Genes, a cold climate and an all-meat diet helped contribute to the Neanderthal’s buff body, the scientists believe. Neanderthal’s dined on mammoths and deer, among other plant-eating animals. The scientists based their research on an analysis of Neanderthal arm bone, dating roughly from 100,000 years ago and found in what is now Russia.

Their findings were published in the journal Archaeology, Ethnology and Anthropology of Eurasia.

Original article here

Neanderthal Genome Yields Reveals Extensive Interbreeding

May 10, 2010

The researchers identified a catalog of genetic features unique to modern humans by comparing the Neanderthal, human, and chimpanzee genomes. Genes involved in cognitive development, skull structure, energy metabolism, and skin morphology and physiology are among those highlighted in the study as likely to have undergone important changes in recent human evolution.

Santa Cruz CA (SPX) May 10, 2010
After extracting ancient DNA from the 40,000-year-old bones of Neanderthals, scientists have obtained a draft sequence of the Neanderthal genome, yielding important new insights into the evolution of modern humans.

Among the findings, published in the May 7 issue of Science, is evidence that shortly after early modern humans migrated out of Africa, some of them interbred with Neanderthals, leaving bits of Neanderthal DNA sequences scattered through the genomes of present-day non-Africans.

“We can now say that, in all probability, there was gene flow from Neanderthals to modern humans,” said the paper’s first author, Richard E. (Ed) Green of the University of California, Santa Cruz.

Green, now an assistant professor of biomolecular engineering in the Baskin School of Engineering at UC Santa Cruz, began working on the Neanderthal genome as a postdoctoral researcher at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

Svante Paabo, director of the institute’s genetics department, leads the Neanderthal Genome Project, which involves an international consortium of researchers. David Reich, a population geneticist at the Broad Institute of MIT and Harvard, also played a leading role in the new study and the ongoing investigation of the Neanderthal genome.

“The Neanderthal genome sequence allows us to begin to define all those features in our genome where we differ from all other organisms on the planet, including our closest evolutionary relative, the Neanderthals,” Paabo said.

The researchers identified a catalog of genetic features unique to modern humans by comparing the Neanderthal, human, and chimpanzee genomes. Genes involved in cognitive development, skull structure, energy metabolism, and skin morphology and physiology are among those highlighted in the study as likely to have undergone important changes in recent human evolution.

“With this paper, we are just scratching the surface,” Green said. “The Neanderthal genome is a goldmine of information about recent human evolution, and it will be put to use for years to come.”

Neanderthals lived in much of Europe and western Asia before dying out 30,000 years ago. They coexisted with humans in Europe for thousands of years, and fossil evidence led some scientists to speculate that interbreeding may have occurred there. But the Neanderthal DNA signal shows up not only in the genomes of Europeans, but also in people from East Asia and Papua New Guinea, where Neanderthals never lived.

“The scenario is not what most people had envisioned,” Green said. “We found the genetic signal of Neanderthals in all the non-African genomes, meaning that the admixture occurred early on, probably in the Middle East, and is shared with all descendants of the early humans who migrated out of Africa.”

The study did not address the functional significance of the finding that between 1 and 4 percent of the genomes of non-Africans is derived from Neanderthals. But Green said there is no evidence that anything genetically important came over from Neanderthals. “The signal is sparsely distributed across the genome, just a ‘bread crumbs’ clue of what happened in the past,” he said. “If there was something that conferred a fitness advantage, we probably would have found it already by comparing human genomes.”

The draft sequence of the Neanderthal genome is composed of more than 3 billion nucleotides–the “letters” of the genetic code (A, C, T, and G) that are strung together in DNA. The sequence was derived from DNA extracted from three Neanderthal bones found in the Vindiga Cave in Croatia; smaller amounts of sequence data were also obtained from three bones from other sites. Two of the Vindiga bones could be dated by carbon-dating of collagen and were found to be about 38,000 and 44,000 years old.

Deriving a genome sequence–representing the genetic code on all of an organism’s chromosomes–from such ancient DNA is a remarkable technological feat. The Neanderthal bones were not well preserved, and more than 95 percent of the DNA extracted from them came from bacteria and other organisms that had colonized the bone. The DNA itself was degraded into small fragments and had been chemically modified in many places.

The researchers had to develop special methods to extract the Neanderthal DNA and ensure that it was not contaminated with human DNA. They used new sequencing technology to obtain sequence data directly from the extracted DNA without amplifying it first. Although genome scientists like to sequence a genome at least four or five times to ensure accuracy, most of the Neanderthal genome has been covered only one to two times so far.

The draft Neanderthal sequence is probably riddled with errors, Green said, but having the human and chimpanzee genomes for comparison makes it extremely useful despite its limitations. Places where humans differ from chimps, while Neanderthals still have the ancestral chimp sequence, may represent uniquely human genetic traits.

Such comparisons enabled the researchers to catalog the genetic changes that have become fixed or have risen to high frequency in modern humans during the past few hundred thousand years.

“It sheds light on a critical time in human evolution since we diverged from Neanderthals,” Green said. “What adaptive changes occurred in the past 300,000 years as we were becoming fully modern humans? That’s what I find most exciting. Right now we are still in the realm of identifying candidates for further study.”

The ancestral lineages of humans and chimpanzees are thought to have diverged about 5 or 6 million years ago. By analyzing the Neanderthal genome and genomes of present-day humans, Green and his colleagues estimated that the ancestral populations of Neanderthals and modern humans separated between 270,000 and 440,000 years ago.

The evidence for more recent gene flow between Neanderthals and humans came from an analysis showing that Neanderthals are more closely related to some present-day humans than to others.

The researchers looked at places where the DNA sequence is known to vary among individuals by a single “letter.” Comparing different individuals with Neanderthals, they asked how frequently the Neanderthal sequence matches that of different humans.

The frequency of Neanderthal matches would be the same for all human populations if gene flow between Neanderthals and humans stopped before human populations began to develop genetic differences. But that’s not what the study found. Looking at a diverse set of modern humans–including individuals from Southern Africa, West Africa, Papua New Guinea, China, and Western Europe–the researchers found that the frequency of Neanderthal matches is higher for non-Africans than for Africans.

According to Green, even a very small number of instances of interbreeding could account for these results. The researchers estimated that the gene flow from Neanderthals to humans occurred between 50,000 and 80,000 years ago. The best explanation is that the admixture occurred when early humans left Africa and encountered Neanderthals for the first time.

“How these peoples would have interacted culturally is not something we can speculate on in any meaningful way. But knowing there was gene flow is important, and it is fascinating to think about how that may have happened,” Green said.

The researchers were not able to rule out one possible alternative explanation for their findings. In that scenario, the signal they detected could represent an ancient genetic substructure that existed within Africa, such that the ancestral population of present-day non-Africans was more closely related to Neanderthals than was the ancestral population of present-day Africans. “We think that’s not the case, but we can’t rule it out,” Green said.

The researchers expect many new findings to emerge from ongoing investigations of the Neanderthal genome and other ancient genetic sequences. Paabo’s group recently found evidence of a previously unknown type of hominid after analyzing DNA extracted from what they had thought was a Neanderthal finger bone found in Siberia. Green is also taking part in that continuing investigation.

Original article here

Second find of ancient dug-out canoe in Arklow by same man

April 23, 2010

A construction crew working on a highway in 1955 pulled up this dugout canoe from a Dutch bog. It’s almost 9 feet long and was radiocarbon-dated to 8500 B.C.

Tim O’Brien/Irish Times

For the second time in half a century, the remains of what appears to be a dug-out canoe have been discovered in Arklow, Co Wicklow. In a curious coincidence, both finds were by the same person, local man Peter Dempsey.

The National Museum of Ireland confirmed yesterday that the first discovery made in 1966 was a dug-out canoe which was recorded and photographed by the museum at the time.

Mr Dempsey, who is mayor of Arklow, said he was feeding ducks on the riverbank close to the locally known 19-arch bridge, when he saw the second canoe last Friday.

As the original canoe had been returned to the water after a record was made by the museum, Mr Dempsey said he initially thought his latest discovery was the same canoe.

However, Nessa O’Connor of the National Museum said photographs appeared to suggest it was a second canoe. Ms O’Connor said personnel from the museum would travel to Arklow to view the find, but from an initial perusal of the photographs, she said there was a strong likelihood that it was indeed a canoe.

Fashioned from trees as primitive boats, the canoes could be as much as 5,000 years old. The longest dug-out canoe found in Ireland is currently in the National Museum. With a length of about 56ft, it was found in Co Galway. It is thought it served as a primitive ferry.

While his first find was returned to the water, Mr Dempsey is hopeful space can be found for the latest discovery in the Maritime Museum in Arklow.

The dug-out requires a lot of care and must be kept immersed in water to stop it from drying out and disintegrating. It is currently being looked after in a local house where it is wrapped in wet bed sheets and regularly hosed down

“I think it may have floated down to Arklow after floods in March,” Mr Dempsey said.

The mayor said he had been telling his grandchildren about his 1966 find moments before he went outside to feed ducks on the riverbank and saw the latest find.

“I wondered was it the same canoe or was it part of it, but it seems to be a completely different one,” he said.

Original article here

Cro Magnon skull shows that our brains have shrunk

April 20, 2010
Cro  Magnon brain

A 3D image of a Cro Magnon brain. Credit: Times Online.

March 15, 2010 by Lisa Zyga

(PhysOrg.com) — A new replica of an early modern human brain has provided further evidence for the theory that the human brain has been shrinking. The skull belonged to an elderly Cro Magnon man, whose skeleton is called Cro Magnon 1. The entire skeleton was discovered in 1868 in the Cro Magnon cave in Dordogne, France, and has since become one of the most famous Upper Palaeolithic skeletons. Using new technology, researchers have produced a replica of the 28,000-year-old brain and found that it is about 15-20% larger than our brains.

To produce the brain replica, called an endocast, the scientists first digitally scanned the interior of the empty skull. The images revealed the impression left by the brain on the neurocranium, which was then transformed into a 3D image. Software was then used to fabricate the brain endocast.

The researchers, including Antoine Balzeau of the French Museum of Natural History, said that an initial assessment of Cro Magnon 1’s skull supported the theory that brains have grown slightly smaller over the past tens of thousands of years, reversing an earlier trend toward larger brains.

The finding doesn’t suggest that humans today are less intelligent than earlier humans. Although previous studies have found a very small relationship between brain size and intelligence, many other factors affect brain intelligence.

For instance, different parts of the brain have different functions. The researchers found that the Cro Magnon brain appears to have had a smaller – the brain region linked to motor control and language – than our brains today. The researchers explain that this finding shows that some parts of the brain are more “compressible” than others, while other regions seem to provide a benefit by growing larger.

Although scientists don’t know for sure why our overall brains are shrinking, some researchers hypothesize that our brains are becoming more efficient as they grow smaller. Having a large comes at a cost, so smaller brains have an advantage since they enable the body to use the extra energy for other purposes. On the other hand, perhaps a large skull had certain advantages for earlier people. One idea is that Cro Magnons needed large skulls because of the difficulty in chewing their food, which included lots of meat such as rabbits, foxes, and horses. Since our food has become easier to eat, we don’t need such large skulls or jaws. Another theory is that the high infant mortality rate in earlier times meant that young humans had to be physically robust (with large heads) to survive their early years.

The researchers plan to show a mold of the later this week at the National Museum of Natural History in Washington, DC.

Neither Neanderthal nor sapiens: new human relative IDed

March 30, 2010
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.