Multiregional hypothesis
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The multiregional origin hypothesis of human origins holds that some, or all, of the genetic variation between the contemporary human races is attributable to genetic inheritance from hominid species, or subspecies, that were geographically dispersed throughout Asia, and possibly Europe and Australasia, prior to the evolution of modern Homo sapiens (conventionally dated to at least 70,000, possibly 150,000, years ago).
Candidate populations suggested by multi-regionalists as sources for such genetic variation include Homo neanderthalensis and Peking Man (a local subspecies of Homo erectus).
This view contrasts with the single origin hypothesis, which holds that modern Homo sapiens evolved from a single, geographically localised, ancestral hominid population, whose descendants ultimately replaced all other species of hominids over the course of tens of thousands of years without interbreeding or subspeciation.
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Proponents of multiregionalism
Two of the scientists most closely associated with the multiregional hypothesis are Carleton S. Coon and Milford H. Wolpoff.
Wolpoff, however, distinguishes his own views from Coon's as follows:
- "Since its inception in the 1980s, multiregional evolution has never been polyphyletic. It has always been a theory about intraspecific evolutionary processes with an emphasis on gene flow... multiregional evolution [is not] a polyphyletic model of parallel racial evolution similar to that of Carleton Coon’s in the 1960s." [1] (http://human-nature.com/nibbs/02/wolpoff.html)
However, Coon was explicit in the exposition of his theory that gene flow between populations played a substantial role in human evolution, a point often overlooked by his critics.
Recent evidence
The multi-regional hypothesis was originally developed from the fossil evidence, but more recent work has focused on molecular data, in which DNA is sequenced. In particular, work has been done with non-recombining DNA such as mitochondrial DNA and the Y chromosome.
For instance, in 2001, a team of Chinese scientists wrote: "all Y-chromosome samples from China, with no exception, were originally derived from a lineage of African origin. Hence, we conclude that even a very minor contribution of in situ hominid origin in China cannot be supported by the Y-chromosome evidence." [2] (http://www.kiz.ac.cn/compgenegroup1/papers/Chinese%20Science%20Bullitin.pdf) In a related publication, scientists in Asia, the US, and the UK examined the Y-chromosomes of more than 12,000 people from across Asia and found no traces of any ancient non-African influence. [3] (http://hpgl.stanford.edu/publications/Science_2001_v292_p1151.pdf) One of the co-authors of the second study, multiregionalist opponent R. Spencer Wells, is quoted as saying "This really puts the nail in the coffin of multiregionalism". [4] (http://web.archive.org/web/20021202001638/news.bbc.co.uk/1/hi/sci/tech/1323485.stm)
Nevertheless, proponents of multiregionalism such as Wolpoff believe the molecular data can not only be reconciled with the multiregional origin hypothesis but in fact in some cases supports it. For instance, studies on past population bottlenecks that can be inferred from molecular data have led them to conclude that the single-origin hypothesis is untenable. One of the co-authors of a 1999 study, proponent John Hawks, is quoted as saying that the single-origin theory "can be put to rest". [5] (http://www.umich.edu/~urecord/9900/Jan17_00/12.htm)
See also
External links
- Origins of Modern Humans: Multiregional or Out of Africa? (2001) (http://www.actionbioscience.org/evolution/johanson.html) A paleoanthropolist argues against multi-regionalism.