Two wave model?

New article out from The American Journal of Human Genetics. I have cut & pasted the abstract below in the “extended entry.” The title is: Haplotypes in the Dystrophin DNA Segment Point to a Mosaic Origin of Modern Human Diversity. Yes, a mouthfull, but basically it is suggesting an added layer of complexity to the standard Out-Of-Africa One-Wave model. I have already expressed doubt about the simplistic Great Leap Forward and summarized the position of some researchers that the Out-Of-Africa scenario is perhaps multi-pronged rather than an explosive blitzkrieg. I’m not saying this particular study will be validated (three dozen locii does not a new model make)-but the flat serene simplicity of the Out-Of-Africa model pioneered by Chris Stringer and reinforced by Alan Wilson is going to get some wrinkles. Age does that to you….

Haplotypes in the Dystrophin DNA Segment Point to a Mosaic Origin of Modern Human Diversity

Ewa Zitkiewicz,1,4 Vania Yotova,1 Dominik Gehl,1 Tina Wambach,1 Isabel Arrieta,5 Mark Batzer,6 David E. C. Cole,7 Peter Hechtman,3 Feige Kaplan,3 David Modiano,8 Jean-Paul Moisan,9 Roman Michalski,10 and Damian Labuda1,2

1Centre de Recherche de l’Hôpital Sainte-Justine and 2Département de Pédiatrie, Université de Montréal, and 3Departments of Human Genetics and Pediatrics, McGill University, Montréal; 4Institute of Human Genetics, Polish Academy of Sciences, Poznan, Poland; 5Departamento Biologia Animal y Genetica, Universidad del Pais Vasco, Bilbao, Spain; 6Department of Biological Sciences, Biological Computation and Visualization Center, Louisiana State University, Baton Rouge; 7Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto; 8Fondazione Pasteur Cenci-Bolognetti, Istituto di Parassitologia, Universita “La Sapienza,” Rome; 9Centre Hospitalier Régional et Universitaire, Nantes, France; and 10Prince Albert Parkland Health Region, Victoria Hospital, Prince Albert, Canada

Received March 31, 2003; accepted for publication July 23, 2003; electronically published September 25, 2003.
Although Africa has played a central role in human evolutionary history, certain studies have suggested that not all contemporary human genetic diversity is of recent African origin. We investigated 35 simple polymorphic sites and one Tn microsatellite in an 8-kb segment of the dystrophin gene. We found 86 haplotypes in 1,343 chromosomes from around the world. Although a classical out-of-Africa topology was observed in trees based on the variant frequencies, the tree of haplotype sequences reveals three lineages accounting for present-day diversity. The proportion of new recombinants and the diversity of the Tn microsatellite were used to estimate the age of haplotype lineages and the time of colonization events. The lineage that underwent the great expansion originated in Africa prior to the Upper Paleolithic (27,00056,000 years ago). A second group, of structurally distinct haplotypes that occupy a central position on the tree, has never left Africa. The third lineage is represented by the haplotype that lies closest to the root, is virtually absent in Africa, and appears older than the recent out-of-Africa expansion. We propose that this lineage could have left Africa before the expansion (as early as 160,000 years ago) and admixed, outside of Africa, with the expanding lineage. Contemporary human diversity, although dominated by the recently expanded African lineage, thus represents a mosaic of different contributions.

Posted by razib at 11:52 PM

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