In the same issue as Wilson and Cann presented the 'Out of Africa 2' or 'Eve Hypothesis' Alan G. Thorne and Milford H. Wolpoff argued the polygenic or multiregional side of the modern human origins debate. They maintain that there is no single recent dispersal for modern humans, that humans originated in Africa and then slowly developed their modern forms in every area of the Old World. They also argue that the molecular geneticists' view must be rejected because their reasoning is flawed. Here follows a summation of their arguments.
According to the multiregional view, mtDNA is not our only source of evidence. Fossil remains and artifacts represent a much more reliable and a monumental body of evidence. Multiregional evolution traces all populations to humans first leaving Africa over 1 mya (now known to be about 1.8 mya). Today distinctive populations maintain physical differences. The features that distinguish Asians, Australian Aborigines and Europeans are said to have evolved over a long period where these peoples are found today.
Thorne and Wolpoff argue that the fossil record, stretching back for a million years, is the real evidence for human evolution. Their self-described goal is "to describe a theory that synthesizes everything known about modern human fossils, archaeology and genes." They outline their own five predictions of the Eve theory, that modern humans from Africa completely replaced all other groups, that the earliest modern humans appeared in Africa, therefore that the earliest modern humans in other areas should have African features, that modern humans have never interbred with earlier populations, and that an anatomic discontinuity should be evident.
The claim that a replacement could occur rapidly in every climate and environment is unprecedented from their 1992 viewpoint. At the time of their writing the volcanic winter bottleneck scenario was not yet presented. The authors point out that if replacement occurred we would expect to find archaeological traces, yet we can find none in Asia. The hand ax was common in Africa, yet the technologies of eastern Asia did not include handaxes before or after the African dispersal period. Artifacts found in the earliest assemblages continue to appear into the very late Pleistocene.
The hominid fossils from Australasia are argued to show a continuous anatomic sequence, with the earliest Australians displaying features seen in Indonesia 100,000 years ago. Similar evidence is seen in northern Asia. One million years old Chinese fossils differ from Javan fossils in ways that parallel the differences between north Asians and Australians today. Morphological continuity is also evidenced by prominently shoveled maxillary incisors occurring in high frequency in living east Asians and in all the earlier Asian fossils. They point out the fact that the Neanderthals and modern humans in the Near East shared an identical culture. They also argue that the Neanderthals were not fully replaced. The more recent DNA isolation from Neanderthal fossils counters this belief.
Thorne and Wolpoff also cite the potential for genetic drift, that some mtDNA disappears every time a generation fails to have daughters. Each lost branch alters the estimation of coalescence to a more recent date. Population size is also addressed, especially the shrinking of population in the Northern Hemisphere due to the Ice Ages. Reductions exacerbate genetic drift and loss of mtDNA types. Therefore, they contend, the lengths of mitochondrial lineages does not actually reflect the age of their divergence. They also criticize the dependence of the Eve model on a molecular clock as unreliable.
Finally, it is affirmatively argued that the close genetic similarities of the entire human race reflect linkages between people, an ancient history of population connections and mate exchanges, or, in other words, gene exchange.
Thorne, Alan G. and Milford H. Wolpoff. 1992. The Multiregional Evolution of Humans. Scientific American 266:76-83.
Recommended: African Eve: Hoax or Hypothesis?