I have to wonder: how come we already have 15 Neandertal mtDNA sequence and less than a handful of Pleistocene Homo sapiens? My guess is that the latter may often turn out to be more similar to extant human mtDNA, making them more "suspect" for contamination.
Figure 2 shows the three Neandertal groups.
PLoS ONE doi:10.1371/journal.pone.0005151
Genetic Evidence of Geographical Groups among Neanderthals
Virginie Fabre et al.
Abstract
The Neanderthals are a well-distinguished Middle Pleistocene population which inhabited a vast geographical area extending from Europe to western Asia and the Middle East. Since the 1950s paleoanthropological studies have suggested variability in this group. Different sub-groups have been identified in western Europe, in southern Europe and in the Middle East. On the other hand, since 1997, research has been published in paleogenetics, carried out on 15 mtDNA sequences from 12 Neanderthals. In this paper we used a new methodology derived from different bioinformatic models based on data from genetics, demography and paleoanthropology. The adequacy of each model was measured by comparisons between simulated results (obtained by BayesianSSC software) and those estimated from nucleotide sequences (obtained by DNAsp4 software). The conclusions of this study are consistent with existing paleoanthropological research and show that Neanderthals can be divided into at least three groups: one in western Europe, a second in the Southern area and a third in western Asia. Moreover, it seems from our results that the size of the Neanderthal population was not constant and that some migration occurred among the demes.
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5 comments:
My guess is that the latter may often turn out to be more similar to extant human mtDNA, making them more "suspect" for contamination.Good guess, I'd say. I can imagine demonstrations of irated "Recentists" at the gates of major universities and labs with posters reading "contaminated is not demonstrated!" and stuff like that. ;-)
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It's notable that the Caucasus specimen clusters with the Western group (though in some of the work models would rather fit with the Eastern or Central Asian group) and that the El Sidron (North Spain) specimen also clusters with the Western group (and again in one work model would instead cluster with the Southern group of Italy and Croatia).
It is also notable that in work model 2 (similar to K=2, so to say, as it only allows for two clusters) the two resulting clusters are Western (all Europe but Caucasus) and Eastern (Central Asia and Caucasus).
Neanderthals can be divided into at least three groups: one in western Europe, a second in the Southern area and a third in western Asia.This must be a typo because the third cluster is actualy located in Central Asia. No West Asian specimens were studied in fact.
The known Neandertal sequences, other than the Vindija specimen, come from bones that produced between 25 and 90 percent modern human mtDNA sequence. So we know a priori that sequence contamination is going to be present in a high fraction. So far sequencing efforts have prioritized Neandertals for that reason, and also because the root of the effort is to find specimens suitable for further nuclear DNA recovery. Serre et al. (2004) went so far as to probe later specimens for the Neandertal-specific variants, but not sequence them.
Hasn't there been some suggestion, at an earlier time, that there was apparently at least as much variation between Neandertal groups, as there is between "modern" human groups?
Anne G
Just on the basis of cranial morphology, I've long thought Amud I and Vindija looked very different from the French Neanderthals. Also, at around 5'10" or 5'11", Amud certainly didn't have the stereotypical short Neanderthal stature.
"it seems from our results that the size of the Neanderthal population was not constant and that some migration occurred among the demes".
How absolutely surprising! Wouldn't we have expected that?
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