Born in Africa_ The Quest for the Origins of Human Life - Martin Meredith [81]
Little attention was paid at first to Weidenreich’s theory of multiregional evolution. The prevailing view remained that Neanderthals were an evolutionary dead-end, replaced some 40,000 years ago by another species, the Cro-Magnons. But during the 1960s, an influential American palaeoanthropologist, Loring Brace, took up the cause of the Neanderthals once again. ‘I suggest’, Brace wrote in 1964, ‘that it was the fate of the Neanderthal to give rise to modern man, and, as frequently happened to members of the older generation in this changing world, to have been perceived in caricature, rejected and disavowed by their own offspring, Homo sapiens’.
During the 1970s and early 1980s, another generation of scientists—notably Alan Thorne of the Australian National University and Milford Wolpoff of the University of Michigan—revived the idea of a ‘multiregional’ model and gained increasing support for it. By the mid-1980s, the majority view was that although the earliest stages of human evolution had occurred in Africa, other key stages of change and innovation had taken off only after hominids had moved into Eurasia more than 1 million years ago, establishing separate regional groups. The spectacular advances made by Cro-Magnons during Europe’s Upper Pleistocene age were a prime example. By comparison, Africa, it was said, had lagged far behind in cultural achievement during the same period, remaining a backwater of little significance.
The growing consensus among palaeoanthropologists about the multiregional origins of modern humans, however, was rudely shattered in 1987 by new findings by molecular biologists. In a paper published by the journal Nature, a team from the University of California at Berkeley—Allan Wilson, Rebecca Cane and Mark Stoneking—claimed that genetic evidence showed that ‘the modern human family’ had originated as a single genetic line in Africa within the last 200,000 years, and not as multiple separate evolutionary events in different parts of the world. Their findings were based on a statistical study of mitochondrial DNA (mtDNA), a special form of DNA that resides not in the nucleus of a cell but in its mitochondria and that is inherited not from both parents but from the mother alone, allowing a trace to be made from living people via generations of mothers into the distant past.
By analysing mtDNA from 147 women from different ethnic groups—Asians, aboriginal Australians, aboriginal New Guineans, Caucasians and ‘Africans’—the Berkeley biochemists constructed a genetic tree that identified a common ancestor living in Africa between 142,500 and 285,000 years ago, therefore probably about 200,000 years ago. ‘All these mitochondrial DNAs stem from one woman who is postulated to have lived about 200,000 years ago, probably in Africa’, they declared. ‘[A]ll present-day humans are descendants of that African population’.
While the world’s media duly celebrated the discovery of an ‘African Eve’, the scientific community was engulfed in fierce infighting. Palaeoanthropologists in the multiregional camp were furious that upstart biochemists, armed with nothing more than blood samples and computers, had invaded their terrain. ‘The fossil record is the real evidence for human evolution’, declared Alan Thorne and Milford Wolpoff in an article in Scientific American. ‘Unlike the genetic data, fossils can be matched to the predictions of theories about the past without relying on a long list of assumptions’.
The multiregionalists pointed out the shortcomings of the Berkeley study. It