Abstract
Cann et al. have claimed on the basis of mitochondrial DNA (mtDNA) data that our direct ancestral Homo sapiens evolved in the African continent and spread to other continents, followed by the total replacement of the indigenous population. Their “Out-of-Africa” model is based on the assumption that mtDNA inheritance is simply maternal. Recent findings suggest the possibility that in between-population, e.g. African and Asian, mating, the African paternal mtDNA was transferred to the egg cell of an Asian together with Y-chromosomal DNA in the human past. Considering that Y-chromos- omal DNA and mtDNA sequences of African origin coexist together with Asian X-chromos- omal and autosomal DNA sequences in a current Asian, the observations by Cann et al. suggest the full/near full replacement of mtDNA in the human past, but do not necessarily imply the total replacement of indigenous populations with African migrants.
Highlights
Evidence has accumulated that the Homo lineage originally appeared in Africa, followed by its successful global expansion
Current non-Africans and thus much more paternal (African) men carry the M168 mutation, which arose in Africa during the period of 89 KY to 35 KY ago [41,42,43]
All of these sequences on Y-chromosome were much younger than those (1,860 KY to 535 KY ago) of X-chromosomal DNA sequences, e.g. gene coded for pyruvate dehydrogenase E1α [44] and non-coding sequences Xq [45], and autosomal DNA sequences, e.g. gene coded for β-globin [46] and non-coding sequences on chromosome 22 [47]
Summary
Evidence has accumulated that the Homo lineage originally appeared in Africa, followed by its successful global expansion. Morphological continuity in East Asian traits from East Asian Homo erectus during the middle-late Pleistocene transition can be seen in these fossil records [12,13,14] Most of these records have neither definitely refuted nor supported one of the models for or against the origin of H. sapiens, in Asia. In 1987, a crucial observation was made by Cann et al, who examined the human mitochondrial DNA (mt DNA) diversity of globally dispersed populations They concluded that modern humans spread to other continents, e.g. East Asia, from Eastern Africa around 200,000 years to 50,000 years (200 KY to 50 KY) ago, followed by the total replacement of pre-inhabited indigenous populations [1,2]. A metaanalysis of these findings has raised the need of careful scrutiny in the interpretation of Cann et al [1,2]
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