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Thanks, Bill for the link to this nice summary. Now I understand. We are not talking about introgression between species but "subspecies". Free interbreeding between subspecies of the same species are part of the definition (our definition, of course) of subspecies. There are no genetic barriers. In this case I find all hypotheses mentioned in that summary "reasonable scenarios". Somebody, earlier on the list (sorry don't remember who) already said that it is only necessary that H. erectus becomes H. sapiens. That we seperate the involved taxa on the species level is artificial and in this case obviously misleading. Biologically, we are talking about an anagenetic process not a phylogenetic one, and 'erectus' might be better called H. sapiens erectus. In this sense, Wolpoff's 'regional continuity model' is perfectly acceptable. And it does not at all imply that modern H. sapiens evolved iteratively. "H. s. erectus" (:-), may have regionally developed different superficial characters but the process did apparently not lead to genetic isolation and allowed interbreeding as the summary and the laddered fork (Wolpoff's original graph???) suggests. So the fork spikes are between regional variants (at most), i.e. still anagenetic. Apologies for my misunderstanding of the problem. Cheers, Niko > >Evolution of separate populations of Homo sapiens could have happened if > H. > >erectus and H. sapiens populations experienced introgression in more than > one > >place. This seems like a reasonable scenario. - SH > > This is the genetic way of expressing the "partial replacement model" > summarized in the link Ana Pinto posted in an earlier message. > http://www.cartage.org.lb/en/themes/Sciences/LifeScience/PhysicalAnthropology/HumanGeneticEvolution/EarlyModern/EarlyModern.htm > > A figure from that page still bothers me. Both the trees for the > "replacement model" and the "regional continuity model" both show > separate transitions from H. erectus to "archaic" H. sapiens on > different continents with modern H. sapiens "out of Africa" replacing > the archaic form while the "regional continuity model" show repeated > introgression events. > > It doesn't seem any more likely that the archaic form of sapiens > would develop independently than would any other form. > > Is this willingness to accept separate origins of the same species > induced (at least in part) from vague memories of pre-plate tectonic > puzzlement over identical shallow-water and terrestrial species > showing up in widely separated locations? > > Bill > -- > --------------------------------------------------- > William P. Chaisson > Adjunct Assistant Professor > Department of Earth and Environmental Sciences > University of Rochester > Rochester, NY 14627 > 607-387-3892 -- --- ADDRESS: Dept. de Geologia/Unitat Paleontologia, Universitat Autònoma de Barcelona, Campus, Edifici Cs, 08193 Bellaterra (Cerdanyola del Vallès), Catalunya, SPAIN --- Tel xx34-93-581-1464/Fax -1263 --- n.malchus@gmx.net (admits larger attachments) nikolaus.malchus@uab.es (max. 2MB for attachments) ---
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