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Out of Africa's Eden: The People of the World
A glance at a South African crowd - blacks, whites, Indians, Chinese, coloureds - seems to hammer home the message that we are a vastly diverse society.
But we're not all that diverse at all, according to paediatrician, geneticist and author Dr Stephen Oppenheimer, who has set out to trace the early movement of humanity in his work Out of Africa's Eden, The Peopling of the World, published by Jonathan Ball.
His theory is that about 80,000 years ago, a group of several hundred people living in Africa set out to cross into the Middle East.
Although a few previous human species had already left Africa, this was the first step in the migrations of our own species - Homo sapiens - from Africa around the world. And scientists have traced mitochondrial DNA links (the DNA that is passed down unchanged from mother to daughter) from all modern humans outside Africa to a woman in that group 80,000 years ago, says Oppenheimer.
Going further back over 150,000 years, previous mitochondrial DNA research has linked a woman living with ancient humans in central Africa to all people alive today. But it is the theory of that departure from Africa, and the subsequent migrations around the globe that fascinates Oppenheimer.
He argues that descendants of these people reached the Malay peninsula by 74,000 years ago and Australia by 70,000 years ago. An earlier exodus to the Levant - or Middle East - had already died out 90,000 years ago.
Oppenheimer proposes that South Asia was the fount of all non-African dispersals and it is possible South China could have been colonised at the same time as South East Asia, about 68 000 years ago.
His view of the future is not rosy. He predicts another freeze-up from a further ice-age cycle or from over exploitation of resources.
He is also worried that our total genetic diversity remains relatively low and our lack of diversity as a species lays us open to new pandemics of infection in crowded, interacting communities.
Oppenheimer writes that random diversity is nature's and evolution's fuel depot. Without randomly generated genetic diversity, species lack the flexibility to survive and adapt to the various stresses imposed upon them.
We are under constant evolutionary stress, especially regarding fast-evolving viruses, such as HIV.
Oppenheimer has worked extensively in South East Asia, Africa and the Pacific but he and his family now live in England, where he is connected to Oxford University.
Oppenheimer visited Cape Town recently and a Cape Argus books page team caught up with him.
He admitted that while writing the book, he kept one eye on the sciences involved. So to get the most out of this comprehensive work, you need to have at least a passing interest in genetics, archaeology, anthropology, oceanography, geology and climatology.
The book encompasses aspects of all these sciences, and uses the work of leading scientists to trace the spread of this type of mitochondrial DNA around the globe.
This fascinating and important work could change the way you think about early humans. It is impeccably put together with a long preface, a clear series of graphics, succinct epilogue and detailed bibliography.
He immediately made it clear that he viewed the less favoured theory that different human groups had developed regionally from different older human species as “racist”. He also admitted that there had been more papers published on the idea that modern people came out of Africa in a series of migrations, rather than in a single exodus.
He said while there was literature on the single exit idea, his was the only book published on the subject.
Oppenheimer said the book was an “obsession” during the two years it took to write. He felt the work done by scientists on the theory of a single common female root for everybody living outside Africa, and the single exit theory, needed to be synthesised into a cohesive work. It is supported by the genetics, that modern humans arose in Africa, moved out and replaced everybody else - and completely. There is no trace of any of the earlier species of humans - who were known to have left Africa previously - to be found in modern humans, certainly not in the mitochondrial DNA,” said Oppenheimer.
“I argue very much for a single exodus, based on the structure of the African (family) tree. All those who are not Africans belong to the same twig, if there had been waves (of migrations of Homo sapiens) they wouldn't all belong to the same twig. It's a logical thing.”
Oppenheimer points out that a lot of of physical anthropology and archaeology was done before the genetic work came to the fore.
The initial genetic work was published in the late 1980s and created a genetic tree which originated in Africa. That tree has since been refined and has evolved into a “very accurate tree”.
Asked how he became interested in genetics, he replied: “I am a paediatrician by trade and worked most of my life in the tropics. But using genetic markers to trace migrations is something that interested me.”
“Right from the time of my thesis work in the early 1980s, when I was working in New Guinea, because there were genetic markers there which traced the migration of the Polynesians, that interest and obsession just got greater and greater.
“I eventually decided to write a book and found an agent and wrote a proposal which she sent to publishers. They liked it and I wrote my first book,” he said.
This was his book, Eden in the East: The Drowned Continent of Southeast Asia, that challenged the orthodox view of Polynesians having been rice farmers from Taiwan.
He said: “That was specifically about migration in the Pacific regions about the Polynesians.” The BBC Discovery Channel also made a documentary “The Real Eve” based on “Out of Eden”.
Oppenheimer is a scientist through and through. He speaks with mild disdain about the “fantasy” written on the outer edges of science.
He says he hasn't got another book in mind at the moment. “But I can see myself getting back into the subject again, not on this scope. I will focus on something in particular.”
No doubt the“something in particular” will again challenge the orthodox view.
Genetic facts and theories in Stephen Oppenheimer's latest book include:
~ A group living in central Africa 150,000 years ago are the ancestors of everyone living today.
~ Everybody who is not African can be connected by mitochondrial DNA to a single woman who apparently left Africa with a band of humans 80 000 years ago.
~ New genetic trees lead straight back to Africa in the past 100 000 years; no traces of Adam and Eve genes from older human species remain, except at the root.
~ Neanderthals have been genetically typed using ancient mitochondrial DNA and now appear to be cousins, rather than ancestors.
~ About 80% of modern Europeans are descended from hunter-gatherer gene types, and only 20% from farmers from the Near East.
~ The genetic tree debunks the theory that Polynesians came from Taiwan; the ancestors of the sailors of the great canoes started out in eastern Indonesia.
~ Geneticists generally believe most founding American lines entered the continent between 30,000 and 22,000 years ago.
~ About 99% of the work that has been carried out into the recon-struction of genetic gene trees was done using modern DNA given by people living all over the world.
November 7, 2003
This article was found at www.capeargus.co.za
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