By PENNY FANNIN
Saturday 13 January 2001
Dr Alan Thorne in his Canberra home. He and his Australian National University team are studying the oldest known Human DNA in a skeleton found near Lake Mungo.
For thousands of years Aborigines wandered among the Walls of China, a line of ancient sand and clay landforms stretching for almost 30 kilometres along the edge of Lake Mungo. When the lake, part of the Willandra Lakes region in south-west New South Wales, dried up about 10,000 years ago,(End of the ice age), the bones and relics of the people who lived on its shores were swallowed up by the desert sands. But 30 years ago, the wind exposed a fragment of history.
In 1969, Australian archaeologists unearthed more than 175 bone fragments. Reassembled, they formed the frame of an adult female, who became known as Mungo Woman. Radio-carbon dating showed she had died between 24,500 and 26,500 years ago.
Then, five years later, 500 metres from where Mungo Woman was discovered, the burial site of another ancient human was found. Jim Bowler, now a professor of earth sciences at Melbourne University, noticed a tip of bone protruding from the sand. The bone turned out to be the top of a human skull at least 25,000 years old. The skeleton was dubbed Mungo Man.
Almost from the moment of its exhumation Mungo Man has challenged scientific beliefs and divided anthropologists. After 25 years there is still no agreement on the age of Mungo Man. Some say 30,000 years, others 60,000. Even the skeleton's sex is disputed, although it is generally considered to be male.
Yet the debates have paled in comparison with the controversy that now surrounds Mungo Man. An article soon to be published by three Australian scientists claims the skeleton proves the prevailing view of the origins of modern humans is wrong.
For more than a decade two theories have competed to explain the origins of Homo sapiens. The more accepted of these is the Out of Africa theory, proposed by Allan Wilson and Rebecca Cann from the University of California, Berkeley, in 1988. This has modern humans originating in Africa about 200,000 to 250,000 years ago and spreading around the globe. During this exodus they wiped out Neandertals and became the dominant species. Wilson and Cann also argue that an "archaic" human species, Homo erectus, had left Africa up to two million years ago and it was this species' descendants, including Neandertals, who were replaced.
But that theory is disputed by Dr Alan Thorne, a visiting fellow at the Australian National University's research school of Pacific and Asian studies. Thorne, along with Professor Milford Wolpoff of the University of Michigan, has long championed what is known as the "multi-region" theory.
The two scientists agree that Homo erectus began in Africa about two million years ago, and migrated. But they believe that Homo sapiens did not evolve solely in Africa but simultaneously in Africa, Europe and Asia.
"There's only two theories, and one of them has to be wrong," says Thorne. In a study to be published in the Proceedings of the National Academy of Sciences USA, he and his two co-authors argue that a new examination of Mungo Man shows the "multi-region" theory must be right.
Acrimony between supporters of the different evolutionary views might appear to be little more than an inflated difference of opinion, but it goes much deeper. For centuries it has been argued that differences between human "races" mean some are inferior, some superior. According to the multi-region theory, the long process of evolution in different regions explains the "differences" between Asians, Africans, Europeans and Aborigines. But if the Out of Africa theory prevails, there can be no genetic basis for racism. Its premise is that modern humans evolved so recently that we are genetically identical, no matter how different we may appear.
So from a pile of bones rises the question: are our differences skin deep or programmed into our genes?
Thorne's argument hinges on the DNA that scientists extracted from Mungo Man. Dr Simon Easteal, an evolutionary geneticist at the ANU's John Curtin School of Medical Research, found that the genetic material contained a small section of mitochondrial DNA. He also analysed genetic material from almost 3500 people, including Neandertals, ancient Aborigines whose remains are about 30,000 years old, and present-day Aborigines. Easteal found that Mungo Man's DNA bore no similarity to the DNA from any other sample.
To Thorne this is dramatic evidence that the Out of Africa theory is wrong. Out of Africa argues that Homo sapiens had a single place of origin. But if Mungo Man was descended from a person who had left Africa in the past 200,000 years, Thorne argues, then his mitochondrial DNA should have resembled the other samples.
Out of Africa distinguishes between Homo erectus and "modern" Homo sapiens. Thorne thinks the distinction is pointless, because it is impossible to define when or where the transition occurred. Out of Africa claims this was Africa, 200,000 years ago.
But Thorne's critics are not persuaded by what he says the DNA shows. Some anthropologists argue that the reason none of Mungo Man's genetic material showed up elsewhere might be because he had no descendants. But until researchers can figure out how to collect nuclear DNA (from the nucleus of human cells) from ancient bones, there is no way of establishing that Mungo Man did not pass on his genes. Mitochondrial DNA is only passed through the female line.
Thorne says the fact that modern Aborigines have the same skeleton and teeth as Mungo Man's shows that while his mitochondrial DNA disappeared, the rest of his genes did not.
University of Sydney prehistorian Peter White says the debate over Mungo Man's mitochondrial DNA is irrelevant to the big picture of evolution. "We're looking at one of those lines of mitochondrial DNA that has disappeared; the fact that it is not known in Australia is meaningless in a larger evolutionary sense."
EVEN without the genetic analysis, Thorne argues, Mungo Man's anatomy is evidence enough for the multi-region theory. "The problem is that no living Australian looks like anyone in Africa," says Thorne. "If people got out of Africa 100,000 years ago, as the Out of Africa theory suggests, they would not have had time to change their appearance so dramatically."
But White says Thorne is overstating the anatomical differences between modern humans. "The difference between African, European and Aboriginal skeletons is really pretty small and there's an enormous amount of overlap between them. To pick out one individual and say he is not like an African is way beyond the evidence."
How long it takes for a species to evolve is still debated among biologists. But if they ever agree on a minimum time for the process, the age of Mungo Man could prove critical.
Thorne thinks Mungo Man is about 60,000 years old (an age that would substantially increase the length of time Australia has been known to have been inhabited). But geologist Jim Bowler, who discovered the skeleton, thinks its age is closer to 45,000 years.
Bowler claims Thorne's ANU dating team "largely ignored" field evidence that showed Mungo Man couldn't have been as old as 60,000 years. Clay pellets in the grave indicate it was dug from a higher, and, therefore, younger, level of sand, says Bowler.
In an article in Australasian Science last year, Thorne suggested the clay had been sprinkled on Mungo Man's body as part of the burial ceremony. Bowler is sceptical. "It's a landscape of clay dunes. To infer clay was sprinkled over the grave of the Aboriginal is absolute nonsense."
Dr Peter Brown, a senior lecturer in archaeology and paleoanthropology at the University of New England, is also sceptical about Thorne's conclusions on the age of the Mungo skeleton. He doubts that genetic material was extracted from it at all.
Brown says the oldest specimens from which genetic material have been extracted are about 30,000 years old, and these had been preserved in ideal conditions - a cool, dry environment. The Willandra Lakes, where Mungo Man was unearthed, are hot, with a fluctuating climate, making it unlikely, Brown thinks, that genetic material could be preserved there.
Brown also challenges Thorne's claim that early humans remained on the same evolutionary path by interbreeding. The geographical distances involved were too great, he says. "In the multi-regional model, it's unlikely gene flow could have been maintained. It's much more likely that modern humans came out of Africa."
Bowler agrees. "I would be surprised if one bit of DNA changes these theories. There seems to be an inverse relationship between the amount of data and the degree of debate."
More than one skeleton will be needed to provide an answer. Perhaps Lake Mungo will offer up further clues to guide the way. (I'm a multi-regionalist)
Or there's the other possibility that they are BOTH WRONG!
Of course, the argument raised by the modern Monogenesists that seeks to trivialize racial differences on the basis of a common human ancestor 150,000 years ago, is absurd on its face. Whether or not the races of man developed immediately before the historic period, or at a vastly earlier period; races are clearly works in progress. One can demonstrate profound changes in types of ability and definable traits from selective breeding patterns in a very few generations. So the argument--relied upon by Clinton and the like, in their recitation of how few genetic factors actually control our differences--is absolutely meaningless.
Men have clearly been racially different for longer than Beagles have been different from Foxes or Wolves, or whatever their nearest cousins may be; and the human differences are just as profound. That doesn't put anyone down. It is simply an acknowledgement of how unique we all are.
William Flax Return Of The Gods Web Site
It is painful to read our liberal rags in search of articles such as yours. Thanks for saving me from the pain of having to go to "the media" in search of information.
Further, Africa is about the only place where a extant megafauna still exists. Current thinking about the extinction of pleistocece megafauna in Australia, Eurasia and North AMerica points to the activity of human hunters. The theory is that in those areas, the megafauna evolved without the presence of early human hunters, hence had not evolved defensive fear of them. This resulted in the rapid extermination of all megafaunal species in those areas with the arrival of Human Hunters. Only in Africa, where the megafauna presumably evolved in the presence of developing human hunters, was a defensive fear mechanism towards these creatures evolved.
In addition, the "biological clock" theory used recently by geneticists has come under question with respect to timing. The Biological clock theory assumes that genetic mutations occur at a constant rate over long time intervals. This is a big assumption, as genetic mutations are subject to external environmental factors which may have had significant influence on the rates of evolution.
IF Homo erectus independently evolved over time all over the world to prduce the same new species indepdently everywhere, this would indeed be a zoological miracle. All evidence indicates that evolution occurs in isolated populations of other species. The newly evolved species then moves out into new territory.
Personally, I believe that either (a) Homo erectus and Homo sapiens were really the same species and any difference between them and us is due to temporal and or geographic variation, or Homo sapiens evolved in Africa and moved out into Eurasia, interbreeding with existing populations of Homo erectus already there which had developed geographic variations which in turn created the different modern races of man. I think Human beings, in the arrogance of their species, tend to MAGNIFY the significance of differences between the skeletal remains of pre-modern human populations and modern Europeans.
For instance, I believe if you could take a Neanderthal, give him a bath, shave, haircut and some deoderant and put him in a business suit, he would not really stand out much in a modern city. He would just look like a stocky, strongly built "foreigner" of some kind.