John Hawks says:
UPDATE (11/8/2006): My colleague, Greg Cochran, has a post at GNXP discussing introgression and microcephalin further:
If this pans out the way we think it will, introgression from Neanderthals (and maybe with other archaics) may have been one of the two fundamental patterns underlying recent human evolution.
One of the two. [my emphasis -Razib]
What could John Hawks mean??? 1) Look at the category I placed this post under 2) Oh yes...a new round of teasing starts. But you won't have to wait that long this time....
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I've been talking about introgression for a year right now. I've been waiting for the papers on this topic to come out, and the first has. If you haven't, please read the posts from Greg and John Hawks. Another paper is on the way, and Hawks promises something within this week. I strongly…
John Hawks, along with Gene Expression regular Greg Cochran, has published a paper (PDF) on adaptive introgression in human evolution. In case the jargon is too much, we're talking about the caveman gene. Both Greg and John have blogged the paper. Check out what John says about mtDNA:
However,…
Update II: Follow up post. You really should read Greg and John Hawks, seeing as how they have a paper in the pipeline on this topic which is stepping off from where Lahn et. al. left off.
Update: Greg and John Hawks have much more must read stuff!
Read about it here. Here is the paper, Evidence…
This is more for google, but if you missed anything, you should check it out. Here is a replay of the introgression & Neandertal related posts....
Preview:
Neandertal & H. sapiens sapiens interbreeding
Neandertal-"modern" mixing
Introgression related posts over the past 6 months
Main course…
The intelligent designer of coarse!
one of the two
My guess is that the other would be something accompanying/facilitating the settlement of humans in larger and more densely spaced groups, as agriculture arose and then intensified in certain regularly flooding river valleys of the greater middle east.
I.e. something in the neighborhood of 5k BP as contrasted with the Neanderthal/archaic introgression in the 30k neighborhood.
To continue with the speculation (hey it's particularly rife around here at the moment), the first one greater brain size particularly in visiospatial areas (though aren't native Aussies supposed to have some outsized visual mapping abilities? is that different in biologic substrate from the 'bold hunter' Neanderthal gift?)
Second one verbal IQ boost together with maybe some personality differences.
None of this should be too greatly overestimated of course since after all the IQ differences between human groups who are raised in even arguably similar nutritional /environmental circumstances aren't THAT enormous.
Probably no more than three standard deviations.
My best guess for "the other of the two" is sickle-cell type stuff, though not confined only to disease-prevention. Cochran recently co-authored a paper w/ Harpending on adapted genotypes vs adapted genes. The latter are mostly or all benefit, little or no cost, while the former are more benefit than cost, though high-cost (sickle-cell). Adapted genes are so optimal that they'll take longer for natural selection to find -- unless some other pop has already invented the wheel for us. Then we'd pick it up by introgression from them. That's pretty much the only way adapted genes will be picked up in the short-run.
Adapted genotypes are easier to find but uglier and are compromises to quickly cope with massive recent environmental change. Obviously new epidemics of infectious disease qualify, but remember the Ashkenazi intelligence paper used the same line of reasoning, but the selective pressure was social. Presumably any other massive, abrupt social shift will induce similar quick-fixes. Personality traits are most up for grabs here since it's easier for the adaptive landscape to change w.r.t. behavioral strategies than capacities like intelligence, though that's fair game too. And again, defenses for malaria, small pox, and so on.
Two of Greg Cochran's articles from 2006 focused on what I assume is "the other pattern" -- not picking up an allele that's mostly or all benefit and little to no cost, but a different pattern, which could respond to social environmental changes...