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[QUOTE]Originally posted by xyyman: [QB] As TP posted above…..much more work is needed but the answer may be buried in the Sahara. -- Second, [b]the MSY tree is deeper than previously believed. [/b]The present figure of about 140 KY for the inferred most recent common ancestor (MRCA) of the MSY phylogeny is older than previous estimates (about 100 KY or below)33–35 and easier to reconcile with plausible scenarios of modern human origin.36 [b]Clearly, calculation of the precise age of the tree largely depends on the accuracy of the assumed mutation rate.[/b] In any case, an antiquity of the root greater than that previously estimated is evident from the present tree structure. It is worth noting that A1b, long neglected in previous large-scale resequencing studies of the MSY, contributes to the older TMRCA and high nucleotide diversity values that we observe, highlighting the importance of targeted studies on rare haplogroups. Third, [b]contrary to previous phylogeny-based conclusions, 15,16 the deepest clades of the revised MSYphylogeny are currently found in central and northwest Africa. [/b]MSY lineages from these regions coalesce at an older time (142 KY) [b]than do those from east and south Africa (105 KY),[/b] opening new perspectives concerning early modern human evolution. [b]A scenario of a Y chromosome ‘‘Adam’’ living in central-northwest Africa about 140 KY ago would provide a good fit to the present data.[/b] However, we also note that, because of the [b]still largely incomplete geographic coverage of the African MSY diversity and unknown consequences of past population processes such as growth, extinction, and migration, any phylogeny-[/b]based inference on the geographical origin of human MSY diversity in Africa should be made with caution. Additional Y chromosome data and future discoveries in other disciplines are required in order to provide crucial information in support of the proposed scenario. Interestingly, there is an accumulation of a growing body of evidence that indicates that African regions that have been long neglected in studies on the origin of Homo sapiens [b]may have been important early sites of modern human occupation, possibly connected to other areas of the continent by routes that are hidden today[/b] (see 37 and references therein). In conclusion, we present here a Y chromosome phylogenetic tree deeply revised in its root and earliest branches. [b]Our data do not uphold previous models of Y chromosomal emergence[/b]15,16 and demand a reevaluation of some fundamental ideas concerning the early history of the human genetic diversity we find today.38–40 [b]Our phylogeny shows a root in central-northwest Africa. Although this point requires further attention,[/b] we think that it offers a new prospect from which to view the initial development of our species in Africa. [/QB][/QUOTE]
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