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.
Fascinating article about the origins of architecture found in the anatomy of animals.
More pictures in the original article, here, at the Canadian Centre for Architecture.
Who was the Archigram of mammoth bones? … Geoff Manaugh
Cedric Price, Neanderthal: or, the Archigram of Mammoth Bones
In Steven Mithen’s fantastic book After the Ice, a natural history of human culture from 20,000–5,000 BC, we find a brief introduction to the earliest architectural structures.
“The world at 20,000 BC is inhospitable,” Mithen writes, “a cold, dry and windy planet with frequent storms and a dust-laden atmosphere… People survive wherever they can, struggling with freezing temperatures and persistent drought.” Their survival is assisted by the construction of shelters—architecture at its very Ice Age origins.
For instance, “five dwellings form a rough circle on the tundra,” Mithen writes, referring to an archaeological site in what is now Ukraine (and using the present tense that his book maintains throughout).
The dwellings are igloo-like but built from mammoth bone and hide rather than blocks of ice. Each has an imposing entrance formed by two tusks, up-ended to form an arch. The walls use massive leg bones as vertical supports, between which jawbones have been stacked chin-down to create a thick barrier to the cold and wind. Further tusks are used on the roof to weigh down hides and sods of turf that are supported on a framework of bones and branches.
Skulls are used as furniture, and animal hides line the floor and walls, in a kind of corporeal grotesque that would make Ed Gein proud. These structures formed what the Field Museum in Chicago calls “small villages of bone huts,” adding that, when a bone didn’t work as architecture, it could be repurposed as a musical instrument—as if predating David Byrne’s Playing the Building installation by more than twenty millennia.
In his book The Archaeology of Animals, Simon J. M. Davis refers to these structures as a type of “osteo-architecture,” or “bone ruins.” He goes on to explain that an archaeologist named Ivan Pidoplichko “excavated some of the most spectacular bone ‘ruins’ so far found in the Ukraine. At Mezhirich, in the Cherkassy Region for example, he found a ‘ruin’ consisting of 385 mammoth bones covering a circular area 4-5m across. Beneath these bones Pidoplichko found 4600 artefacts and an ash-filled circular pit.” Davis’s ensuing description is worth quoting in full:
In Pidoplichko’s reconstruction the building was shaped like a beehive, similar to a Chukot Yaranga or ‘skin tent’ of today. The base of the structure consisted of a circle of some 25 mammoth skulls, each arranged so that its frontal bones faced inwards (this was how he found them). Other elements which made up the foundation were 20 mammoth pelvises and 10 long bones embedded vertically in the ground. On top of these and the skulls were 12 more skulls, 30 scapulae, 20 long bones, 15 pelvises and segments of seven vertebral columns. Still higher—and presumably for holding down skins over a wooden framework—there were 35 tusks. Ninety-five mammoth mandibles, piled up in columns around parts of the foundation, may have served as a peripheral retaining wall.
Mithen speculates that these anatomical Ice Age building supplies did not come only from coordinated acts of hunting (in which slaughtering large animals would also have meant obtaining spare parts for your house, as if wooly mammoths were a kind of living Home Depot). Instead, he suggests, “the river supplies building materials: bones from animals that have died in the north and had their carcasses washed downstream.” These bones thus arrived by, and were harvested from, deltaic processes of the nearby watershed, just a particularly bulky form of sediment or debris for which it was easy to find a cultural use.
There are several architectural points to be made here. First, it seems substantially more interesting to me to locate the birth of architecture in actual paleolithic practices, not in the terminological vagaries of early Greek philosophy (which seems to the prevalent mode of searching for architecture’s theoretical origins today). But what if the knee-joints of extinct megafauna are more important for the origins of architecture than Daedalus or khôra?
In other words, why not perform forensic studies of mammoth bones and animal skins, and put down the Plato? As a side note, I was intrigued to see that the Wikipedia page for the history of architecture, as of June 2010, does not even go beyond 10,000 BC, starting instead with the Neolithic. But what of Steven Mithen, Davis’s osteo-architecture, and our bone-encircled Ukrainians?
At what point is an inhabitable pile of skulls considered a building?
Second, what was architectural “style” 22,000 years ago? Were there eccentric or personalized methods for tying sinew bone-to-bone, or virtuoso tactics for assembling antlers into windproof screens on difficult hillside sites? Who were the path-breakers for the time—who was the Cedric Price of animal architecture, or the Archigram of mammoth bones? By extension, what palaces of mastodon ribs have been lost to archaeology altogether? Multi-floored labyrinths of cartilage and bearskin rugs. An Early Holocene Plug-In City made from the jaws of saber-toothed tigers.
Third, surely a retrospective exhibition of late Pleistocene architecture is long overdue? Even a small gallery show exploring the state of architecture 22,000 years ago would be extraordinarily interesting. At the very least, imagine the weekend outreach programs for kids.
The border between natural history and architectural design deserves far more exploration, beyond the odd science museum diorama. We have been living in buildings for more than 20,000 years, if Mithen’s book is to be believed, but nearly half of that period has seemingly been thrown outside the pale of architectural history.
Buildings, however, did not suddenly appear at 10,000 BC with the first stonemasons, woodcutters, or certified Greek philosophers; they accumulated out of the corpse-filled debris of Ice Age rivers when neurologically modern humans began to interlock and assemble bones into structures of which we have almost no physical record.
So how do we bring these structures out of material anthropology and into architectural history, where they just as equally belong?
Dig up cattails. Remove starchy roots and rhizomes. Peel outer layer, dry, and grind into flour with two rocks. Mix with water and cook. Bon appetit!
The Paleolithic diet, it turns out, may have consisted of more than just meat and berries. At three sites in Italy, Russia and the Czech Republic, scientists have discovered tools that would make a Stone Age Crate and Barrel manager burst with pride:Mortars and pestles for grinding grains.
The mortars are flat stones, while the pestles are pointed andshaped to fit the hand. They all show wear from grinding, as well as microscopic bits of “flour” embedded in them. The flour appears to have been ground from the starchiest, underground parts of cattails, ferns and other plants.
Anthropologists have assumed that early humans supplemented their meaty, protein-heavy diet with nutrients from plants. Plant starches are energy-rich carbohydrates, but aren’t exactly “ready-to-eat.” The latest discovery confirms that humans as far back as 30,000 years had figured out how to “process” some of those starches before consuming them.
Writing in the journal Proceedings of the National Academy of Sciences, the scientists suggest that the flour ground in the mortar and pestle would eventually have been cooked. Raw starch is pretty hard to stomach and doesn’t offer much nutrition until the tough grains are broken down by heat. (See Harvard primatologist Richard Wrangham’s book Catching Fire: How Cooking Made Us Human for more on this.)
In terms of the energy it provided, the cattail flour is pretty similar to Emmer wheat (known as farro in Italy). It’s been a staple of European cooking for millennia that’s believed to have fed the marching Roman legions.
As for taste, the researchers didn’t report results. But without yeast or sugar or even salt, chances are cattail bread wasn’t terribly tasty.
But memorable? Well, we’re still writing about it.
NRK, the norwegian state channel does it again: They send redneck norwegian families to live with tribes in Africa and South America to make a reality TV show. The tribes are instructed to wear penis sheaths and be topless, contrary to how they would normally dress, to make the TV images more exciting.
The norwegian participants are hand-picked for ignorance of foreign cultures and contrast in lifestyle. They are not allowed to have translators, which makes for a lot of confusing situations with the visited tribes.
Edited together back in the west, with plenty of breast and penis shots, Norwegian viewers can view with horror the “primitive” lifestyles of indegineous tribes.
This is not a culture exhange, it is pure exploitation. How about making a TV show about how these tribes actually live, and what we might learn from them? Don’t send the most ignorant norwegians there to complain about lack of makeup and fitness centers and Ipods, please!
NRK, we expect better from you – and the people of Norway pay for you to make this crap!
That said, the NRK channels are commercial-free, and they do produce some very good programs. The state-run Norwegian TV and Radio institution has mainly followed the great educational tradition of the BBC. This year the NRK celebrate it’s 50-year jubilee -to bad it has to taint their mostly excellent legacy with this crap!
An apparent Neanderthal sleeping chamber has just been unearthed within Esquilleu Cave in Cantabria, Spain.
The room likely contained grass beds, which served double duty as seats, near a hearth.
Other research supports that Neanderthals constructed such functional living spaces within caves and rock shelters.
Anthropologists have unearthed the remains of an apparent Neanderthal cave sleeping chamber, complete with a hearth and nearby grass beds that might have once been covered with animal fur.
Neanderthals inhabited the cozy Late Pleistocene room, located within Esquilleu Cave in Cantabria, Spain, anywhere between 53,000 to 39,000 years ago, according to a Journal of Archaeological Science paper concerning the discovery.
Living the ultimate clean and literally green lifestyle, the Neanderthals appear to have constructed new beds out of grass every so often, using the old bedding material to help fuel the hearth.
“It is possible that the Neanderthals renewed the bedding each time they visited the cave,” lead author Dan Cabanes told Discovery News.
Cabanes, a researcher at the Weizmann Institute of Science’s Kimmel Center for Archaeological Research, added that these hearth-side beds also likely served as sitting areas during waking hours for the Neanderthals.
“In some way, they were used to make the area near the hearths more comfortable,” he said, mentioning that artifacts collected from various other Neanderthal sites suggest the inhabitants prepared stone tools, cooked, ate and snoozed near warming fires.
For this study, Cabanes and his team collected sediment samples from the Spanish cave. Detailed analysis of the samples allowed the scientists to reconstruct what materials were once present in certain parts of the cave at particular times.
The bedding material was identified based on the presence and arrangement of multiple phytoliths from grasses near the hearth area. Phytoliths are tiny fossilized particles formed of mineral matter by a once-living plant.
There was no evidence of plants growing, soil developing or animal transport of phytoliths via dung, so the scientists believe the only plausible explanation is that Neanderthals gathered the grass and placed it in this room of the cave.
While the hearth contained some grass phytoliths, most belonged to wood and bark, “indicating that this material was the main type of fuel used,” according to the researchers. Some animal bones were also tossed into the hearth, perhaps to dispose of them after dinner and/or for use as extra fire fuel.
Evidence is building that Neanderthals in other locations constructed such functional living spaces within caves and rock shelters.
Earlier this year, Josep Vallverdu of the Catalan Institute of Human Paleoecology and Social Evolution and his team identified a “sleeping activity area” at Spain’s Abric Romani rock shelter.
Similar to the Esquilleu Cave finds, Vallverdu and his colleagues discovered the remains of hearths spaced enough for seating and sleeping areas.
“This set of combustion activity areas suggests analogy with sleeping and resting activity areas of modern foragers,” Vallverdu and his team wrote. They added that such information can allow anthropologists to estimate the size of Neanderthal populations, in addition to learning more about how they lived.
The big question, according to Cabanes, is how such a resourceful species went extinct.
“In my opinion, Neanderthal extinction may have been caused by several factors working at the same time,” he said. “Environmental changes, a slightly different social organization, a different rate of reproduction, spread of diseases, direct competition for resources and many other factors may have played an important role in the fate of Neanderthals.”
He and other researchers have also not ruled out that Neanderthals were simply absorbed into the modern human population.
Cabanes is hopeful that future analysis of phytoliths, as well as other less obvious clues that have often been overlooked by scientists in the past, may shed additional light on the still-mysterious Neanderthals.
An artifact found at a dig at Motala river in Sweden could be an ancient sex toy says this archaeology blog. The Motala find is made from antler and clearly fashioned with a rounded knob at one end. Seeing is believing, some say, but beauty is in the eye of the beholder and the artifact could just as well be interpreted as a tent peg or something else. Surely they masturbated 6000 years ago too, but perhaps not with antlers and stones? If it was sexual, it could just as well have been symbolic, perhaps used in ritual, or maybe even more like a teenage prank.
Oh yeah, and the length? About 12 cm.
No matter what you believe, this interesting find is but part of an important state funded project The Swedish National Heritage Board are conducting at an early stone age site along the Motala river which exits the large lake Vättern in southern Sweden. Here, an advanced community lived 8-6000 years ago, imported their flint from other regions and probably used the waterways to access different geographical areas for food. They have even found a shark tooth at the site (Motala was 35 km inland at that time), perhaps once used like a Cali beach bum or surfer would wear a sharks tooth around their neck in a leather string today.
The site is now in the middle of a town and heavy roads. It is only being investigated because of pending railroad expansions. More about the whole project here.
Another possible ancient phallus was recently found at the much older Hohle Fels Cave outside of Ulm in southern Germany.
Nyligen rapporterades det att världens äldsta dildo hade påträffats i en grotta, Hohle Fels Cave utanför Ulm i södra Tyskland. Ett forskarteam som undersökte platsen under ledning av Professor Nicholas Conard tolkade ett av stenföremålen, 20 cm långt och 3 cm tjockt, som ”ett möjligt sexverktyg”. Föremålet bär emellertid även spår efter att ha använts för flinthantverk.
Undersökningen vid Strandvägen utmanar med att ställa frågan om vi har hittat Skandinaviens äldsta dildo? Föremålet är ett bearbetat horn som utan omsvep för tankarna till en fallos. Vad tycker Du?
Fallosar påträffas vanligtvis i sammanhang som hör till yngre perioder, framförallt järnålder, där vissa hällristningar och statyer avbildar guden Frej med erigerad penis. Symbolen kopplas till fruktbarhet. Från stenålderslokaler i Europa är det vanligt att finna kvinnliga fruktbarhetssymboler liknande Venus från Willendorf. Däremot är manliga fruktbarhetssymboler ovanliga.
Fyndet vi gjort är ett bearbetat och slipat horn, ca tolv centimeter långt och två centimeter i diameter. Formen är avsiktligt framarbetad. Föremålet stack fram ur blålera i ett skottkärrelass. Fynden knyts till de stratigrafiskt äldsta skeendena på platsen, det vill säga äldre stenålder. I samma lager har vi även hittat ytterligare ett snidat horn, flera ristade horn, ett stort antal ljusterspetsar samt ett tiotal mindre depositioner av människoben. Detta ger nya inblickar i äldre stenålderns föreställningsvärld.
– Först trodde jag (Sara) att det bara var ett bearbetat horn och skulle titta lite närmare på det. Men när jag höll upp den kunde jag inte hålla skrattet tillbaka. Och snart utbröt ett allmänt fnitter i hela sålltältet.
Dagen avslutades storstilat med besök av fem yngre, atletiska män som utan större bekymmer slängde av sig kläderna och badade från en avstängd järnvägsbro 50 meter från våra såll. Vi hoppas på kärt återseende.
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.
Archaeologists reported on Tuesday that they have found the earliest evidence of Neanderthals living in Britain. Two pieces of flint dating back 110,000 years ago were found at a construction site in Dartford, Kent. Dr. Francis Wendan-Smith, from Southampton University, said the finds push back the presence of Neanderthals in Britain by 40,000 years or more. A majority of researchers believe Britain was uninhabited by humans during the time the flint tools date back too.
An absence of archaeological evidence suggests people abandoned this land between 200,000 years ago and 65,000 years ago. However, one researcher said the evidence presented so far did not convince him. Dr. Mark White from Durham University told BBC News he would like to assess the findings in detail before considering whether they posed a challenge to the majority view that humans were absent from Britain at this time.
The excavation that uncovered the flint hand tool and waste flake was funded by the U.K.’s Highways Agency. Wenban-Smith and colleagues from Oxford Archaeology have dated the sediments back 110,00 years, placing them within the “abandonment period.” The discovery comes from a time when sea levels were dropping after a period when they were high enough to make the English Channel impassable.
“We know that Neanderthals inhabited Northern France at this time, but this new evidence suggests that as soon as sea levels dropped, and a ‘land bridge’ appeared across the English Channel, they made the journey by foot to Kent,” Wenban-Smith told BBC. The dearth of evidence for human occupation in Britain between 200,000 and 65,000 years ago has perplexed the archaeologists. The English Channel would have posed a physical barrier to humans trying to cross the continent. However, sea levels fluctuated during this period. There were other times when hunters could walk from France to southern England.
About 200,000 – 130,000 years ago the sea level was predominantly low. Humans should have been able to get there, but for some reason they did not show up. “It could be something subtle like the rapidity of changing climate, altering its state from warmer to colder conditions. That may have meant it was too hard for the Neanderthals to develop a sustainable adaptation,” Wenban-Smith told BBC. “Neanderthals were cold adapted and maybe it just took them that time to adapt to the cold environment of that period. Before 130,000, they had not really cracked it. But after 115,000, they had cracked it.”
About 130,000 years ago sea levels rose and Neanderthals would have been blocked from entering Britain by the English Channel. However, about 115,000 years ago sea levels fell again. Wenban-Smith and his team said the flint tools from Dartford suggest that humans were able to take advantage of this opportunity. The discovery was dated back by using a method known as optically stimulated luminescence (OSL). This exploits the presence of radioactive isotopes in the natural environment. Naturally occurring minerals like quartz and feldspars record the amount of radiation to which they have been exposed.
Some minerals store a proportion of energy radiation delivered and then release it at a later date in the form of light. The amount of light released by these minerals can be used to calculate the radiation dose a sample has received, helping to give an estimation of time that has elapsed since it was buried. White raised doubts over the reliability of OSL dating though, saying the technique was more or less “in constant development.” He added that assumptions about background radiation and average water content could significantly affect results.
“I haven’t seen the flints, but I’ve no doubt they are genuine. Currently, with what has leaked to the press, I have no idea of the context of these finds,” he told BBC News. “I suspect there is a possibility the OSL dating [technique] might not be giving us the true date. And that would be my only [reservation].” “I have similar dates from a site near Dover in Kent, which have come out between 90,000 and 100,000 years ago. But I don’t think OSL is giving us a correct date and I have disregarded them.”
Neanderthals split from our evolutionary line about 500,000 years ago. A short, muscular physique, a barrel chest, large brain and prominent facial features characterized them. Wenban-Smith along with other researchers say that the “classic” Neanderthal features appeared about 200,000 years ago. However, other scientists describe much older fossils as Neanderthals. These include the 400,000-year-old partial skull found in Kent and the 230,000-year-old human teeth discovered at Pontnewydd in Wales.
The new David H. Koch Hall of Human Origins at the Smithsonian National Museum of Natural History in Washington D. C. explores the history of human evolution over millions of years as our ancestors adapted to a changing world. Here’s a look at some of the items on view.
Via Wall Street Journal.
I’d love to see this exhibition. One thing that strikes me, though, from looking at sculptures and reconstructions made for this exhibition on the website is that they are all very rough guesses at what our ancestors may have looked like, and not definitive at all, yet rendered in a level of detail that the scientific material does not warrant. Since we are spoiled with films and TV-productions of high detail and computer generated graphics, we want to see such detailed images at this kind of exhibition, and the people behind it have decided to go for an ultra-realistic look, much like modern science fiction and fantasy films, and I can understand why. What kid today, spoiled from our exaggerated and highly detailed graphic environment would be impressed by a tiny broken bone flute?
In fact, the less spectacular items on display are the most interesting: artefacts, like the bone flute, faded cave painting fragments, tools and jewelry tell us that these people were very much like us, and that they were occupied with similar intellectual activities. I fear that the Hollywood-like contemporary constructions at this exhibit will look outdated in just a few years, much like exhibits on natural history from the 50’s and 60’s look to us today.
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.