> From: David Hobby <[EMAIL PROTECTED]> > > The Fool wrote: > >> From: Alberto Monteiro <[EMAIL PROTECTED]> > >> > >> The Fool wrote: > >>> Didn't native americans cross the land bridge circa 14,000 years > >>> ago, and remained relatively unconnected to other human > >>> populations until circa 1492? > >>> > >> The key word is "relatively". There is no true isolation. > >> > >>> I'm not buying it. There was no common ancestor as of 2000 ya or > >>> even 3000 ya. > >>> > >> I am - but I think 2000-3000 is too conservative. I would bet that > >> _everybody_ descends from Gengis Khan, who lived less than 1000 ya. > >> > >> > >> The math is too simple: just imagine that "being a descendant of > >> G-K" is a disease, and that the rate of non-infected people gets > >> squared at each generation. > >> > >> Treat semi-isolated groups with care, but once there is contact - a > >> single outsider f---ing a tribe woman - the group will be doomed to > >> be "infected" in a few generations. > > Alberto-- > > I'm with the Fool on this one. There are too many semi-isolated > groups. The Americas were already isolated enough, I bet, so that > there are a few completely full-blooded Indians around. Aboriginal > peoples in Australia, and the New Guinea highlands were probably > more isolated genetically. > > As I recall, New Guinea was split into a huge number of small > tribes, each with a bit of genetic exchange with its neighbors. > If it takes a few generations to infect a tribe, then it could > still take a long time for new genes to diffuse inland. > > > Genetically, I think it was that chinese people are about 8% decended > > from Khan. At least that is what the last thing I read about it > > said. > > The Fool-- > > You mean something like this quote: > > > Research published in the American Journal of Human Genetics in 2003 > > suggested that 16 to 17 million men, most in Central Asia, shared a > > form of the Y chromosome that indicates a common ancestor. > > If so, note that it just looks at descent through the male line, > since that's what you get by analyzing the Y chromosome. This > does not count descent through females. At a guess, this increases > the number of descendants a lot, say up to 95% of everyone of Eurasian > descent. > > > I think your math is off. Otherwise there would be a much more even > > distribution of alleles. > > No, there doesn't have to be much gene flow at all for > everyone to have a recent common ancestor. This is the > gist of Alberto's argument that "one fvck can infect a > tribe". All it takes is a little bit of gene flow.
1st generation children would have about 23 chromosomes from lone invader-parent. 2nd gen would have on average 11-12 chromosomes. 3rd gen would have on average 6 chromosomes. 4th gen would have on average 3 chromosomes. 5th gen would have on average 1-2 chromosomes. 6th gen would on average have 1 or less chromosomes. This ignores selection of course. At an average of 2 surviving children per generation, there would at generation 6 be about 64 decendents with aproximately 1 chromosome. The Lone Invader Parent had 46 chromosomes, as compared to about 64 individual surviving chomosomes in his descendents, most of them duplicates. (This ignores inbreeding, which is endemicic in certain populations, mostly arabic, that for reasons of maintaining property rights, marry first cousins). An Actual Inverse Square-Law as opposed to Alberto's Sqaure-Law. > My objection is that there are a lot of groups which > were sufficiently isolated so that there has not yet > been any flow of outside genes into them to the point > of saturation. Unless you want to postulate that there > was more contact between groups than there is any solid > evidence for... > _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
