I have a question mark in the last case because this idea that we can have a simple to illustrate and verbally elegant "model" that we promulgate across the land might have to go. Parsimony to the back of the class...for now. John already chided me for presenting the old introgression via hybrid zone model as if it was the last word. I think it is important to not place evolutionary dynamics into a demographic box, the history of genes are reticulated, and do not respect our simple narratives. The old Out of Africa model was clean. An assumption of 1:1 correlation between mtDNA phylogenies and homonid demographic history was made which allowed the straight line inference that Africa is the locus of a recent demographic expansion which resulted in the replacement of all other human populations within the last 100,000 years. All mtDNA lineages are derived from African ones. But, all this says necessarily is that it seems that African mitochondrial lineages replaced all others, whether via demographics (e.g., population explosion or larger long term effective population size) or selection. The old Multi-regional model is anagenetic in that "lineages" are simply local subpopulations with particular ecotypes, but all of the various populations are interwoven by persistent gene flow, as well as periodic selective sweeps driven by advantageous alleles arising in subpopulations spreading. There is no lineage splitting.
A more nuanced model doesn't take an extreme position. For example, one can acknowledge that there was a recent demographic expansion out of Africa which characterized the rise of modern humans as we know them, while at the same time acknowledging that the local ecotypes might have persisted via introgression of locally selected alleles. How's that for a mouthful? The short of it is that Neandertals and other archaic species were on the ground in regional habitats for far longer than the expanding Africans. They possessed particular alleles which the Africans didn't have. Just like Europeans picked up maize and potatos from the New World populations, so Africans could have picked up MC1R & MCPH1 alleles which might come in handy. But just because Europeans adopted New World crops as their own does not mean that European culture is derived from New World culture. Similarly, just because local ecotypes were partially assimilated by the expanding African population base does not mean the African populations are now descended from the antecedent populations. Only some of their genes, and perhaps many essential aspects of their phenotype, might resemble the antecedant populations. But if it looks like a duck, and it quacks like a duck...well, you decide.
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And the essential difference between this new spiffy introgression model, and the tired old, uncool, with bad (racialist) associations (cause it was the last model the old school scientific racists of the Carlton Coon era advanced) is exactly what?
Isn't this multiretionalism comes back on steriods (carried on a wave of cold hard empirical evidence to be sure), if we're gonna be honest?
And the essential difference between this new spiffy introgression model, and the tired old, uncool, with bad (racialist) associations (cause it was the last model the old school scientific racists of the Carlton Coon era advanced) is exactly what?
1) in race and human evolution wolpoff & caspari actually go to great pains to point out how their model differs from coon's, whose own ideas were derivative of others
2) coon posited that human racial lineages split on the order of 10 million years ago. this current model would hold that modern human populations split mostly on the order of hundreds of thousands of years, perhaps less than 100,000 assuming mostly african ancestry. that's a pretty big difference
3) whether this is multi-regionalism on steroids or out-of-africa with local assimilation is a philosophical and verbal issue. i'm not too interested in it really. the older models of multi-regionalism seem to strongly lean toward anagenesis, which i don't think the newer model that i'm imagining is totally in line with (i think it can be argued that modern human origins do lay necessarily with a speciation event in africa ~100 K BP)
multi-regionalists and out-of-africanists have both been playing the PC-card for years now. you're really wrong if you think out-of-africa is fundamentally more PC in its packaging, they just have a bigger propoganda budget because they are dominant right now. if you think multi-regionalists aren't PC, you haven't read their stuff, so please stop it with that particular schtick. i really don't care about the political ramifications, i suspect the current model will be complex enough that anyone can spin anything out of it.... (e.g., the idiot racists will be confirmed in their views and the there-are-no-races types will also be confirmed, though you'll have to ask them how they get there).
Well,we can explain how picking up _favorable_ alleles is likely even when overall levels of mixing are quite low (and thus you don't see much non-African neutral stuff).
That's not something I've seen before: Coon, Stringer, etc all seem not to have drunken deeply at the spring of population genetics.
All mtDNA lineages are derived from African ones. But, all this says necessarily is that it seems that African mitochondrial lineages replaced all others, whether via demographics
I am bit confused here. Why only mtDNA lineages? Why not Y-chromosome lineages are included?
What your sketches suggest is that instead of some small number of lines being broadly equal, or only one line mattering at all, one particular line is much 'more equal' than the others. If that's what you wanted me to realise, you've succeeded.
Looking at your profile picture in the upper left hand part of the page, I have to say that you don't look too Bengali to me. More like a Canadian from around 1977. Can't tell if you have a gold chain with a gold horn attached. That would be proof positive.
no one calls me a fucking kanadian! don't post here again.