NOT Out of Africa

NOT Out of Africa

Standard Textbook Theories of Human Origins Are Wrong

Genetics & Genealogy:

Is Out-of-Africa Going Out The Door ?

 

By Kate Wong

 

 

 Out-of-Africa theory posits that modern humans arose in Africa and replaced other human species across the globe

 

 

Re-analysis of gene studies and new fossil evidence cast doubts on a popular theory of human origins.

 

Anthropologists have long debated the origins of modern humanity, and by the mid-1980s two main competing theories emerged. One, Multiregional Evolution, posits that humans arose in Africa some two million years ago, evolved as a single species spread across the Old World and were linked through interbreeding and cultural exchange. The Out-of-Africa hypothesis, in contrast, proposes a much more recent African origin for modern humans - a new species, distinct from Neanderthals and other archaic humans, whom they then replaced. Emphatic support for Out-of-Africa came in 1987, when molecular biologists declared that all living peoples could trace a piece of their genetic legacy back to a woman dubbed "Eve," who lived in Africa 200,000 years ago. Although that original Eve study was later shown to contain fatal flaws, Out-of-Africa has continued to enjoy much molecular affirmation, as researchers have increasingly turned to DNA to decipher the history of our species.

But a closer look at these genetic studies has led some researchers to question whether the molecular data really do bolster the Out-of-Africa model. And striking new fossil data from Portugal and Australia appear to fit much more neatly with the theory of Multiregional Evolution.

The DNA from mitochondria, the cell's energy-producing organelles, has been key Out-of-Africa evidence. Mitochondria are maternally inherited, so genetic variation arises largely from mutation alone. And because mutations have generally been thought to occur randomly and to accumulate at a constant rate, the date for the common mitochondrial DNA (mtDNA) ancestor can theoretically be calculated. This "molecular clock" indicates that the mtDNA ancestor lived a mere 200,000 years ago, and the root of the gene tree traces to Africa. These results, along with the observation that variation is highest in Africa (indicating that modern humans had been in Africa the longest), seemed to offer unambiguous support to a recent African origin for all modern humans.

But the significance of each finding has been questioned. The date is suspect because the molecular clock depends on problematic assumptions, such as the calibration date and mutation rate. And if natural selection has shaped mtDNA, as some studies suggest, then the rate of mutation accumulation may have differed at different times. The African root for the mtDNA gene tree is compatible with Out-of-Africa, but it does not exclude Multiregionalism, which predicts that the common ancestor lived somewhere in the Old World, probably Africa. And neither does the high mtDNA variation in African populations as compared with non-Africans uniquely support Out-of-Africa, according to anthropologist John H. Relethford of the State University of New York College at Oneonta. "You could get the same result if Africa just had more people living there, which makes sense ecologically," he asserts.

Another problem plaguing the genetic analyses, says geneticist Alan R. Templeton of Washington University, lies in a tendency for researchers to draw conclusions based on the particular genetic system under study. "Very few people try to look across all the systems to see the pattern," he observes. Some nuclear genes indicate that archaic Asian populations contributed to the modern human gene pool, and Templeton's own analyses of multiple genetic systems reveal the genetic exchange between populations predicted by Multiregionalism.

Still, Relethford and Templeton's arguments haven't convinced everyone. Henry C. Harpending, a population geneticist at the University of Utah, finds Multiregionalism difficult to swallow because several studies put the prehistoric effective population size - that is, the number of breeding adults - at around 10,000. "There's no way you can get a species going from Peking to Cape Town that's only got 10,000 members," he remarks. (Other researchers counter that this number, based on genetic diversity, may be much smaller than the census size of the population - perhaps by several orders of magnitude). And many geneticists, such as Kenneth K. Kidd of Yale University, insist that "the overwhelming majority of the data is incompatible with any ancient continuity."

But those who believe that Out-of-Africa's genetic fortress is crumbling find confirmation in fresh fossil data that pose new difficulties for the theory's bony underpinnings. Last December researchers unearthed in western Portugal's Lapedo Valley a fossil that preserves in exquisite detail the skeleton of a four-year-old child buried some 24,000 years ago. According to Erik Trinkaus, a Washington University paleoanthropologist who examined the specimen, the team fully expected the remains to represent a modern human, based on its date and the style of the burial. But subsequent analysis, published in the June 22 Proceedings of the National Academy of Sciences USA, revealed a surprising combination of features, such as a modern-looking chin and Neanderthal limb proportions. After reviewing scientific literature on primate hybrids, Trinkaus concluded that this child resulted from interbreeding between Neanderthals and modern humans.

Not everyone is persuaded. Christopher B. Stringer of London's Natural History Museum, lead proponent of the Out-of-Africa model, wonders whether the fossil might simply represent a cold-adapted modern human, because Portugal then was colder than it is today. In any case, Stringer maintains that his model does not exclude occasional interbreeding.

Yet Trinkaus notes that because the fossil is dated to thousands of years after these groups came into contact, "we're looking at populations admixing." Furthermore, adult fossils from central and eastern Europe show the effects of mixing, too, states paleoanthropologist David W. Frayer of the University of Kansas. And if the groups were interbreeding across Europe, asserts University of Michigan multiregionalist Milford H. Wolpoff, "that would mean you could make a strong case that [contemporary] Europeans are the result of the mixture of these different groups." Another name for that, he says, is Multiregional evolution.

Multiregionalism also best explains the surprising new date for a previously known fossil from western New South Wales, according to paleoanthropologist Alan Thorne of the Australian National University. In the June Journal of Human Evolution Thorne and his colleagues report that the fossil, known as Lake Mungo 3, now looks to be some 60,000 years old - nearly twice as old as previously thought - and unlike the other early Australian remains (all of which date to less than 20,000 years ago), this one bears delicate, modern features. To Stringer, this gracile form indicates the arrival of modern humans from Africa, albeit an early one. Over time, he reasons, selection could have led to the robust morphology seen 40,000 years later.

But Thorne argues that such dramatic change is unlikely over such a short period and that fossils from the only environmentally comparable region - southern Africa - show that people have remained gracile over the past 100,000 years. Moreover, Thorne maintains, "there is nothing in the evidence from Australia which says Africa" - not even the Mungo fossil's modern features, which he believes look much more like those of contemporaneous Chinese fossils. And Thorne observes that living indigenous Australians share a special suite of skeletal and dental features with humans who inhabited Indonesia at least 100,000 years ago.

Therefore, he offers, a simpler explanation is that the two populations arrived in Australia at different times - one from China and the other from Indonesia - and mixed, much like what has been proposed for Neanderthals and moderns in Europe. Exactly the same pattern exists in recent history, Thorne adds, pointing to the interbreeding that took place when Europeans arriving in North America and Australia encountered indigenous peoples. "That's what humans do." The mystery of human origins is far from solved, but because DNA may not be as diagnostic as it once seemed, Thorne says, "we're back to the bones." University of Oxford geneticist Rosalind M. Harding agrees. "It's really good that there are things coming from the fossil side that are making people worry about other possibilities," she muses. "It's their time at the moment, and the DNA studies can just take the back seat."

From New Scientist via http://www.ramsdale.org/dna4.htm

Alan Thorne's challenging ideas about human evolution

by Joseph D'Agnese, Photography by Sean Dungan

Anthropologist Alan Thorne holds casts of two of the skulls that have fueled a controversy about how and when early man reached Australia. The delicate skull at right, of a hominid known as Mungo Man, predates the larger, thicker skull on the left by tens of thousands of years, a reversal of expectations that has challenged traditional theories of evolution.

She came to him in 1968, inside a small, cheap suitcase — her burned and shattered bones embedded in six blocks of calcified sand. The field researchers who dug her up in a parched no-man's-land in southeastern Australia suspected that she was tens of thousands of years old. He was 28. Almost every day for the next six months, he painstakingly freed her remains from the sand with a dental drill, prizing out more than 600 bone chips, each no larger than a thumbnail. He washed them carefully with acetic acid, sealed them with a preservative, and pieced them together into a recognizable skeleton. Looking closely at skull fragments, bits of arm bone, and a hint of pelvis, he became convinced that two things were true. First, the bones were human, Homo sapiens for sure, and they had held together a young woman. As he assembled this "monster three-dimensional jigsaw puzzle," Alan Thorne, then a lecturer in the department of anatomy at the University of Sydney, began asking himself whose bones they might actually have been. He had no idea that many years later, the answer to that question would rock the world of anthropology.

    Something else about this woman became clear early on— she had been important and powerful. The pattern of burn marks on her bones showed that after she died, her family burned the corpse, then smashed the bones. Later, they added more fuel and burned the bones a second time. This was an unusual ritual. Ancient Aboriginal women were typically buried without fuss. Thorne wondered if her descendants had tried to ensure that she did not return to haunt them; similar cremation rituals are still practiced by some Aboriginal groups today. As hours and days and months passed, he found himself thinking of her as a living, breathing person who'd spent her life encamped on the shores of Lake Mungo, in New South Wales. If this Mungo Lady turned out to be as ancient as field researchers thought, she would be the oldest human fossil ever found in Australia. To Thorne she was already the most mysterious.

In 1968 most anthropologists thought they had a grip on human evolution: Big-browed, thick-skulled humanoids had descended from walking apes. These hulking creatures were eventually replaced by the more advanced, fine-boned humans of our species— Homo sapiens. Throughout Australia, anthropologists had found only big-browed, thick-skulled fossils. That made Mungo Lady a puzzle. Lab analysis of her remains suggested she was 25,000 years old— old enough to be a grandmother to those specimens— but her skull bones were as delicate as an emu's eggshell. Thorne began to realize that she might be telling him a different story than the one he'd read in textbooks— that the delicate, fine-boned people had reached Australia before the big-brows.

    That was an exotic thought, and now, many years later, it is fueling the debate within anthropology over a single huge question: Where did Homo sapiens come from? Most researchers accept a theory referred to as "out of Africa." It holds that numerous species of hominids— beginning with Homo erectus— began migrating out of Africa almost 2 million years ago and evolved into several species. Then a new species called Homo sapiens evolved in Africa and migrated between 100,000 and 120,000 years ago to Europe, Asia, and Australia, consigning all the earlier hominids it encountered to extinction.

    Thorne preaches a revolutionary view called regional continuity. He believes that the species his opponents insist on calling Homo erectus was in fact Homo sapiens, and that they migrated out of Africa almost 2 million years ago and dispersed throughout Europe and Asia. As he sees it, there was no later migration and replacement: "Only one species of human has ever left Africa, and that is us."

    Why does this matter? Because if Thorne and his camp are right, much of what we think we know about human evolution is wrong. In the world according to Thorne, the human family tree is not divided into discrete species such as Homo erectus, Homo antecessor, Homo heidelbergensis, and Homo neanderthalensis. They are all Homo sapiens. Yes, Thorne agrees, from the outside all these hominids look different from each other, but so do humans today— a Korean, a Nigerian, and a Dane hardly resemble each other. Our ancestors displayed great variety, but they were similar in the only way that mattered: They were the same species, which meant they could have sex with each other and produce fertile offspring.

Mungo Lady started Thorne down the road to regional continuity. Six years after he reassembled her, Thorne and three assistants unearthed another small-boned skeleton only 1,600 feet from where she had been found. At burial, this body had been laid on its right side, knees bent, arms tucked between its legs. Certain features— the skull, the shape of the pelvis, and the length of the long bones— told Thorne he was looking at Mungo Man, which thrilled him. As a general rule, female skeletons are more delicate than male ones, so doubts about the uniqueness of Mungo Lady's delicate bones would be quashed by having an equally delicate male counterpart to study.

    Thorne's colleagues took their best guess at this specimen's age, as they had with Mungo Lady in 1968, based on radiocarbon dating and analysis of stratigraphy. They dated him to 30,000 years ago. As the oldest humans ever found down under, the finds were considered so important that the Australian government declared the sandy, bone-dry crater that was once Lake Mungo a national park in order to honor— and protect— the site. To the Aboriginal tribes, the pair became precious symbols of their early peopling of the continent.

    But Thorne assigned a meaning to the bones that resonated beyond Australia. To his mind, the presence of two such unusual skeletons suggested that the peopling of the Pacific was a richer, more complex process than anyone had ever imagined. Anthropologists had long assumed that the first Homo sapiens to reach Australia were fishermen who left Indonesia and got blown off course, ending up on the new continent. Thorne began to wonder whether the first journey from Indonesia to Australia was not an accident but an adventure, undertaken with confidence by intelligent, mobile people. Mungo Lady and Mungo Man closely resembled skeletons of people living in China at the same time. Had these people migrated in boats to Australia? Had there been successive waves of immigration by different peoples over tens of thousands of years? To imagine such things, Thorne had to abandon familiar notions of early man as a blundering primitive.

    He had already begun to do so. In the months he'd spent piecing together those braincases, he had begun to think of them as his elders, worthy of respect, capable of thought and imagination. That supposition was not an outrageous one for an Australian anthropologist to make. From childhood Thorne had grown up on a continent that was home to one of Earth's oldest continuous cultures. He'd learned a great deal about Aboriginal culture while working his way through college as a reporter at the Sydney Morning Herald. From where he stood, the ways of Mungo Man and Mungo Lady were not so different from those of modern Aborigines. He could easily picture two different tribes settling near Lake Mungo, one from nearby Java, another perhaps with roots in China. And once the two parties were encamped around the lake, it was not hard to imagine them crossbreeding.

    Those who believe in regional continuity tend to have a view of sexuality that is more generous and more inclusive than that of the out-of-Africa proponents. In the latter view, Homo sapiens led a kind of search-and-replace mission as they spread around the planet; these researchers believe that members of the new species would not have been able to successfully reproduce with members of earlier species, no matter how hard they tried. Thorne thinks that's nonsense. "European scientists have dominated this field for 150 years," he says. "And they've got a big problem in Europe. Namely, they've got to account for those Neanderthals. My opponents would say that Cro-Magnons"— humans identical to us who lived during the Ice Age— "simply 'replaced' Neanderthals with no intermingling. That's the part I object to. 'No intermingling.' Now, I ask you, does that sound like the human beings you know?"

    In the early 1970s, these ideas were pure speculation. Thorne had no proof of anything. The bones had told him what they could and then lapsed into silence. So he tucked them away and went on with his career. Three decades later, the bones spoke again. 

Standard Theory - Now Discredited Nonsense

Dueling Theories

Graphic by Matt Zang

In 1997 Thorne finally got the tool he needed to explore Mungo Lady and Mungo Man further. European scientists reported that they had successfully extracted fragments of mitochondrial DNA (mtDNA) from the remains of Neanderthal skeletons unearthed in Germany, Croatia, and Russia. This was stunning science; the Neanderthals had died out 35,000 years ago, and yet researchers had been able to harvest genetic matter from their bones as if they'd expired yesterday.

    It was the beginning of a revolution in paleoanthropology. Geneticists were hooking up with bone men everywhere. They were focusing on mtDNA because the mitochondria, which lie outside the nucleus, are easier to study— in a human cell there are only 37 mitochondrial genes compared with 100,000 genes found in the nucleus— and because it is the only DNA anyone has been able to isolate and interpret in ancient fossils. For reasons not yet understood, mtDNA survives the ravages of time better than nuclear DNA. And it has another interesting attribute: It's inherited only through the maternal line. Scientists seized upon this characteristic to try to build genetic family trees. Almost two years ago, geneticists working in Sweden and Germany reported studying the mtDNA of 53 living people from around the world. Within this small sample, they found that Africans shared a characteristic sequence of mtDNA, and that everyone else carried at least some portion of that sequence in their cells.

The research suggests that all living humans had their roots in Africa. But Thorne doesn't put much stock in this report. He thinks the conclusions are questionable because samples taken in Africa today could be from people whose ancestors were not African.
   

When the first Neanderthal studies were published in 1997, Thorne had already retired. He had traveled the world for 30 years, excavating sites and filming science documentaries for Australian television. His face and his ideas were as well known in Australia as Carl Sagan's once were in the United States. At the request of the Aboriginal council, Thorne still safeguarded the Mungo fossils. Because three more-sophisticated dating technologies were now available, he ordered new tests on 13 of the individuals in his care, and the results gave him a shock. 

 

 Skeletal Puzzle: Far left: Near the site where Mungo Man's skeleton was excavated, Alan Thorne demonstrates the strange pose in which the body was buried 60,000 years ago. Center: In his right hand, Thorne holds a cast of Mungo Lady's charred skull; in his left hand, a cast of Mungo Man's skull. Left: This bone chip is similar in size to the 350-odd chips from which Thorne pieced together Mungo Lady's skull. "Every day I'd sit down and I'd find 10 or so pieces that fit together. I could only work on her 50 minutes at a time, when my mind was fresh. Any longer and they all started to look alike. She took me six months."

The ages came back first. Using the new technologies, his team found that the small-boned Mungo Lady and Mungo Man were actually 60,000 years old— twice as old as anyone had guessed. Thorne saw these dates as a crushing blow to the out-of-Africa theorists. No matter what his opponents said, there wasn't enough time on their 120,000-year clock for Homo sapiens to leave Africa, dash up to China, evolve from rugged Africans into small-framed Asians, invent boats, sail to Australia, march to the interior, get sick, and die. How much simpler everyone's life would be, he thought, if anthropologists could agree that some of the players in this drama had reached China 1.5 million years ago and continued to evolve there.

    After the dating, Gregory Adcock, a doctoral student in genetics at Australian National University, decided to check all 13 fossils for mtDNA. But first he set up stringent procedures. It's easy to contaminate specimens: More than once, scientists have been embarrassed when the "ancient DNA" they extracted turned out to be their own. To avoid this catastrophe, Adcock alone handled the specimens. He alone traveled between two testing labs. He sampled his own DNA and Thorne's to use as a control. Before sampling the ancient specimens, he tested five modern human and animal bones to make sure he'd perfected handling techniques. Then he drilled into each fossil and took a sample from the bone's interior, where no one could ever have touched it. Of more than 60 samples he analyzed, he reported only three contaminations. Ten of the 13 yielded DNA.

    The results were nothing less than remarkable: Among the 10 successful extractions was the world's oldest known human DNA— plucked from none other than Mungo Man. (No DNA was recovered from Mungo Lady, perhaps because she had been cremated.) Mungo Man also appeared to mock the findings of previous scientists: His mtDNA signature did not match anyone's, living or fossil, on Earth. There was no evidence that he was genetically related to ancient Africans.

    The findings were published in January 2001 by Adcock, Thorne, and five other researchers. What followed was intense disagreement. "People just fell over when they read this new stuff," says Alan Mann, an anthropologist at Princeton University and a moderate in the human-origins debate. "The people at Mungo were totally modern looking and were expected to carry the DNA we have, but they didn't. I think that makes for an incredibly complicated story. It's a stunning development."

    Thorne's critics were underwhelmed. "Alan is great at generating media interest. He's a former journalist, you know," says Chris Stringer, head of human origins at the Natural History Museum in London, a staunch advocate of the out-of-Africa model who is accustomed to his phone ringing off the hook every time Thorne fires another volley. "He has done some important work. I'm not saying his work is bad or wrong or whatever. Obviously, I have a different interpretation of it."

    Stringer and his colleagues laid into Thorne. First, they said it was unlikely that 10 of the 13 skeletons had yielded mtDNA. This was an unprecedented success rate, so they believed that there had to be contamination. Even researchers at Oxford University, in one of the world's finest labs, had contaminated specimens. Then they said that mtDNA lines died out all the time; the Australians were making much ado about nothing. This part was true: Twenty-five to 30 percent of mankind's mtDNA has been lost over the past million years when women gave birth to boys or didn't reproduce at all.

    Thorne concedes that mtDNA has evolved greatly over time, and all scientists working in this area have to be cautious. But as long as everyone is using mtDNA analysis as a basis for speculation, he asks why his work is regarded with such suspicion. Mungo Man and his alternative complement of genes were alive enough to make it to Australia and contribute to the peopling of a continent. Modern Aborigines didn't inherit Mungo Man's mtDNA, but they have certainly inherited the characteristics of his skull. "Eventually, all these people intermingled, and that's why the Aborigines have such diversity," he says.

    Stringer, for his part, maintains that the out-of-Africa model could account for a settlement in southern Australia 60,000 years ago. Africans, he says, would have had to travel only one mile toward Australia each year for 10,000 years to make that possible. In other words, the Homo sapiens who left Africa 100,000 years ago would have reached Indonesia with plenty of time to sail to Australia.

    In New York, Ian Tattersall, one of Thorne's closest friends, has long quibbled with his stance. "We've agreed to disagree," says Tattersall, curator of anthropology at the American Museum of Natural History. "I have a lot of respect for him; I just think he's barking up the wrong tree." Tattersall argues that Neanderthals were so obviously a separate species that Homo sapiens could not have bred with them.

    Thorne says his lifelong study of animals has taught him otherwise. In captivity, for example, jaguars have mated with leopards and pumas and produced fertile female offspring— although all three animals supposedly belong to different species. Polar bears and brown bears, wolves and coyotes, dromedaries and Bactrian camels also cross-mate. Darwin himself dismissed species as a term that is "arbitrarily given, for the sake of convenience."

In recent months Thorne and his team have examined every human fossil from Australia and Asia they could get their hands on. They're retesting their Mungo Man work, hoping to confirm the findings and fill in some of the remaining gaps in the fossilized man's mtDNA profile. To satisfy their critics, they are allowing three rival labs to analyze Mungo Man extractions. Results will be available by the end of this year. When they are, they will most likely be debated. This science is still too inchoate for either side to declare victory.

    Whatever the outcome, the bones from Lake Mungo have created change in Australia. The nation has committed to returning Lake Mungo and its environs to the Aborigines. Soon elders of the tribes living around Lake Mungo will decide when they will assume management of the land, artifacts, wildlife, and tourist trade. In 1991, standing near the metal stake that marks the spot where Mungo Lady was found, Thorne returned her bones to the elders of those tribes. At the time, elders debated whether to rebury her or preserve her. Thorne argued for the latter.

"If you do away with her bones," he told them, "I'll always be right. You won't be able to refute my work. Someday there will be an aboriginal Alan Thorne, and he'll have a different way of looking at these bones. You have to give him that chance." The council voted for preservation. Today Mungo Lady inhabits a safe that can be opened only with a key, of which two copies exist. Aboriginal elders hold one; Thorne was presented with the other.

    Despite Thorne's proselytizing, only a small fraction of the world's anthropologists accept his theories. But he couldn't care less. These days, he draws inspiration from the old Sherlock Holmes maxim: "Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth."

    He points out that regional continuity is by far the simpler theory and can much more comfortably account for all the complicated twists and turns in the genetic evidence of human evolution now coming to light. "It argues that what is going on today is what has been going on for 2 million years, that the processes we see today are what have been going on in human populations for a very long time. You don't need a new species that has to extinguish all the other populations in the world. This is why out-of-Africa is the impossible, and regional continuity is not only not improbable but the answer and the truth."

From Discover Magazine @ http://discovermagazine.com/2002/aug/featafrica

A skull that rewrites the history of Humans

By Steve Connor

It has long been agreed that Africa was the sole cradle of human evolution. Then these bones were found in Georgia...

The conventional view of human evolution and how early man colonised the world has been thrown into doubt by a series of stunning palaeontological discoveries suggesting that Africa was not the sole cradle of humankind. Scientists have found a handful of ancient human skulls at an archaeological site two hours from the Georgian capital, Tbilisi, that suggest a Eurasian chapter in the long evolutionary story of man.

The skulls, jawbones and fragments of limb bones suggest that our ancient human ancestors migrated out of Africa far earlier than previously thought and spent a long evolutionary interlude in Eurasia – before moving back into Africa to complete the story of man.

Experts believe fossilised bones unearthed at the medieval village of Dmanisi in the foothills of the Caucuses, and dated to about 1.8 million years ago, are the oldest indisputable remains of humans discovered outside of Africa.

But what has really excited the researchers is the discovery that these early humans (or "hominins") are far more primitive-looking than the Homo erectus humans that were, until now, believed to be the first people to migrate out of Africa about 1 million years ago.

The Dmanisi people had brains that were about 40 per cent smaller than those of Homo erectus and they were much shorter in stature than classical H. erectus skeletons, according to Professor David Lordkipanidze, general director of the Georgia National Museum. "Before our findings, the prevailing view was that humans came out of Africa almost 1 million years ago, that they already had sophisticated stone tools, and that their body anatomy was quite advanced in terms of brain capacity and limb proportions. But what we are finding is quite different," Professor Lordkipanidze said.

"The Dmanisi hominins are the earliest representatives of our own genus – Homo – outside Africa, and they represent the most primitive population of the species Homo erectus to date. They might be ancestral to all later Homo erectus populations, which would suggest a Eurasian origin of Homo erectus."

Speaking at the British Science Festival in Guildford, where he gave the British Council lecture, Professor Lordkipanidze raised the prospect that Homo erectus may have evolved in Eurasia from the more primitive-looking Dmanisi population and then migrated back to Africa to eventually give rise to our own species, Homo sapiens – modern man.

"The question is whether Homo erectus originated in Africa or Eurasia, and if in Eurasia, did we have vice-versa migration? This idea looked very stupid a few years ago, but today it seems not so stupid," he told the festival.

The scientists have discovered a total of five skulls and a solitary jawbone. It is clear that they had relatively small brains, almost a third of the size of modern humans. "They are quite small. Their lower limbs are very human and their upper limbs are still quite archaic and they had very primitive stone tools," Professor Lordkipanidze said. "Their brain capacity is about 600 cubic centimetres. The prevailing view before this discovery was that the humans who first left Africa had a brain size of about 1,000 cubic centimetres."

The only human fossil to predate the Dmanisi specimens are of an archaic species Homo habilis, or "handy man", found only in Africa, which used simple stone tools and lived between about 2.5 million and 1.6 million years ago.

"I'd have to say, if we'd found the Dmanisi fossils 40 years ago, they would have been classified as Homo habilis because of the small brain size. Their brow ridges are not as thick as classical Homo erectus, but their teeth are more H. erectus like," Professor Lordkipanidze said. "All these finds show that the ancestors of these people were much more primitive than we thought. I don't think that we were so lucky as to have found the first travellers out of Africa. Georgia is the cradle of the first Europeans, I would say," he told the meeting.

"What we learnt from the Dmanisi fossils is that they are quite small – between 1.44 metres to 1.5 metres tall. What is interesting is that their lower limbs, their tibia bones, are very human-like so it seems they were very good runners," he said.

He added: "In regards to the question of which came first, enlarged brain size or bipedalism, maybe indirectly this information calls us to think that body anatomy was more important than brain size. While the Dmanisi people were almost modern in their body proportions, and were highly efficient walkers and runners, their arms moved in a different way, and their brains were tiny compared to ours.

"Nevertheless, they were sophisticated tool makers with high social and cognitive skills," he told the science festival, which is run by the British Science Association.

One of the five skulls is of a person who lost all his or her teeth during their lifetime but had still survived for many years despite being completely toothless. This suggests some kind of social organisation based on mutual care, Professor Lordkipanidze said.

From The Independent @  http://www.independent.co.uk/news/science/a-skull-that-rewrites-the-history-of-man-1783861.html

Dmanisi Man and the Out of Africa fairytale

 

 The D2700 skull from Dmanisi

 On exposition in the Naturalis Museum of Leiden, Netherlands 29 november 2009 t/m 28 februari 2010: the Dmanisi Man of Georgia.

A special exposition of the original skull of the earliest humanoid ever found outside of Africa. The find of this skull in Georgia raises a lot of questions on the evolution of humankind all over the world. The high age of 1.8 million year as well as the small braincapacity and the location outside Africa don’t fit into the current theories on the migration of our forebears. For the first time the skull will leave the safe of the National Historic Museum in Tbilisi, Georgia, to be exposed to the public.

I had a quick visit to the Leiden exposition of Dmanisi Man. The information was really very basic since “the book” still has to be written. Who ever said that Dmanisi is old news? Let him send me the articles everybody agree upon. In short, three competing theories were mentioned. No evaluation, the visitors of the exposition are required to decide for themselves.

1. Out of Africa : according to this view Dmanisi Man should somehow fit within the framework of an African exodus of early humans that was theorized to have happened between 1.5 -1 million years ago. However, since Dmanisi Man was about 1.8 million years old he doesn’t fit in this scenario. So do others BTW (from the start this Out of Africa was a fairy tale).

2. Earlier Out of Africa : Human (? not proven) artefacts are known from 2.6 million years ago onward. This theory proposes that the earliest humans thus could have left Africa a lot earlier and reached Asia from 2.6 million years ago onwards. New human species developed in Asia that also reached Europe. Not a word about backmigrations (a weak point).

3. Back and Forth : At any time of history humanids or early humans left Africa, developed into more advanced species and then returned to Africa.

Obviously the third option is less compromised by Afrocentrism, but I could not find additional information: what species left Africa? Were they necessarily human? Should this explain why Homo Erectus could coexist next to Homo Habils as a separate species for so long in Africa, while previously Homo Habilis was considered the ancestor of Homo Erectus? Does the same apply to Homo Habilis in relation to Australopithecus? Of course few can be said, since no African Homo were found between the first artefacts of 2.6 million years ago and the first unequivocal remains of Homo Habilis dated 1.8-1.6 million years ago. Maybe those artefacts were not human at all and rather belong to Australopithecus? There is no evidence, only conjecture.

About the skull: the last molars (wisdom teeth) did not develop yet, so Dmanisi was a teenager. This could explain some about the outrageous low brain capacity. Possibly this skull is the best evidence we can get to prove that the human adolescent growth spurt was already a feature of the very first Homo.

At least superficially it looks quite similar to Homo Habilis. It has a horizontal brow ridge and more protruding zygomatic facial bones in common with Asiatic samples of Homo Erectus, against the V-shaped brow ridge and weaker zygomatic facial bones among the African/European samples. Unfortunately, no dentals were preserved so nothing can be said of this sample about shoveling.

Extrapolating from the Back and Forth model, I can easily imagine Homo Habilis to be from the same stock as the inmediate ancestors of Dmanisi. However, though Asiatic Homo Erectus features are clear and documented, I think the age and intermediate characteristics of Dmanisi do not support a role of this specific human type in the backmigration of Homo Erectus. Maybe rather of Homo Ergaster?

We may even reconsider the human origin completely and remind Von Koenigswald, that located the origin of humans in India. He was already familiar to Homo Modjakertensis and postulated that our predecessors were apes like Dryopithecae, Rampithecae, Sivapithecae that all seem to have either predominantly or exclusively a northern non-African distribution. The question whether or not Australopithecus should be separated completely from the humanoid line would need another evaluation, as well as the position of Afarensis within the Australopithecus family that may be invalid. Maybe the earliest bipeds arrived in a first migration wave from the Eurasia, together with the precursors of Chimpansees and Gorillas, while Lucy (Australopithecus Afarensis) and Homo Rudolfensis/Homo Habilis were the result of subsequent migration waves from Asia?

Assumptions towards an African monopoly on human origins are not getting better, and supply an ever less self-explicatory setting for the Recent Single Origin hypothesis. Its prime assumption that early hominids elsewhere but Africa are ultimately irrelevant, offers an all too easy way out of complexity and thrives on circularity: all hominids originate in Africa, thus all observed characteristics of hominids elsewhere should be assumed to originate in Africa as well. Well, did they?

Such an important assumption should be verified with available evidence. Where is the proof that Homo Erectus of the Far East derives from Homo Habilis? Homo Modjakertensis as intermediate form does not attest a straightforward evolution at all. The Dmanisi find has characteristics in common with Homo Habilis, Australopithecus and Homo Erectus of eastern asia. We should expect Homo Habilis to have evolved to Dmanisi and to Homo Modjakertenis and subsequently to Homo Erectus. In Africa we miss these kind of intermediate forms, the change or development from Homo Habilis to Homo Erectus is thus not assumed straightforward and “treelike”, but “bushlike”. However, the set of Homo Habilis characteristics is even contrary to the assumption of being ancestral: together with Homo Modjakertensis they share the intermediate position between Australopitecus and Homo Erectus having a semicircular ear canal morphology, though they fail to show the “simian gap” what would suggest an advanced development in relation to the earliest Homo Erectus that is not supported by their age.

The controversal features of the Homo Modjakertensis catalogued as “Sangiran 4″ – projecting canines and precanine diastemata – are recently confirmed, and even deemed rather ‘pongid’, ie. derived from Asiatic apes rather than African apes:

This analysis shows that the Sangiran 4 palate is not unique, and shares several of these putative pongid traits with other Javan hominid fossils as well as recently described hominid specimens from Dmanisi, Georgia. These results suggest that the evolution of the earliest Asians was more complex than has previously been appreciated. — The enigma of the Sangiran 4 palate revisited, Arthur C. Durband (2008).

However, the set of characteristic of homo habilis against Dmanisi and/or Homo Modjakertensis also includes some that are not transitional to all modern humans. The most notorious being the shovel-shaped teeth of 80% of mongoloid people. Like Homo Erectus, these can’t be derived unequivocally from Africa and it is hard to imagine that Asiatic food required shovel-shaped teeth already for millions of years and thus to assume parallel evolution. If this comes out this would be a bad day for Asiatic restaurants all over the world, and good news for orthodontists.

The African origin of shovel-shaped teeth among Homo is precarious to say the least, although Australopithecus was reported to have them. The two Homo Habilis mentioned by Tobias for having shovel teeth are suspect finds: the position of OH6 is contested and OH16 was found completely shattered. Hardly convincing for universal currency among all early hominids. Homo Habilis and Homo Erectus coexisted for hundreds of thousand years in Africa, so maybe some evidence became mixed up, or maybe they just mixed. And what happened next?

Trinkhaus 2007: African Middle Paleolithic Modern Humans (MPMH) have chisel teeth. Archaic humans and Neanderthal, that grossly comprise all the rest in this period, have shovel-shaped teeth. Maxillary incisor shoveling remains in the Gravettian among Early European Modern Humans. The wave of chisel teeth thus only took effect much later in Europe.

Moreover, apparently ‘African’ chisel teeth never conquered Asia! The disproportionate presence of shovel teeth in Asiatic populations and the preservation of this characteristic among native Americans within a European civilization is a strong argument for a genetic component above “domestication”.

A relevant African Origin question: Were the “modern” chisel teeth a new evolutionary adaptation that spread from a single source in Africa, or is the chisel shape reminiscent of Homo Habilis and indicative for a minor influence of the mainstream evolutionary line that rather pertains to Homo Erectus? Could we presume continuity? Or if Homo Habilis can now be discarted as an ancestor, and Homo Erectus was an immigrant in Africa: where and how did the shovel teeth of Homo Erectus originate?

For the record, Dmanisi Man should not have come as a surprise. We already knew of 2 million year old tools in Pakistan and Homo Modjakertensis was already dated in the same range half a century ago. So why Out of Africa was ever proposed at all to explain Homo Erectus? The facts show the hypothesis isn’t even overdue: it was all made up from the start.

Evidence ignored for so much time is bound to make sensation today, or tomorrow for that sake. Maybe a disproportionate importance of Anglosaxon scientists and public is the cause of the undue acceptance of Out of Africa? Just imagine that Indonesia would have been a British colony, and some kind of Leakey would have discovered Homo Modjokertensis. And just think what evidence would have been forgotten by the international scientific communitity if Kenia would have been a Dutch colony instead and Von Konigswald the anthropologists that found a few bones in Kenia that after all were just a shadow of the contemporary finds in Indonesia. The Dmanisi would have been the confirmation of what we already knew for a century.

References:

• Erik Trinkaus – European early modern humans and the fate of the Neandertals, 2007, link

• Arthur C. Durband – The enigma of the Sangiran 4 palate revisited, 2008, link (paysite)

• G.H.R. von Koenigswald – De eerste aapmensen in Azië, 1981, ISBN 90 70157 20 9 (Dutch)

• M. Martinón-Torres et al. -Dental evidence on the hominin dispersals, 2007, link

• Christian R. Nichol et al. – Variation in the convexity of the human maxillary incisor labial surface , 1982, link (paysite)

From Rokus @ http://rokus01.wordpress.com/2009/12/08/dmanisi-man-and-the-out-of-africa-fairytale/

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