I have some interest in the field of anthropology and evolution but my knowledge in these fields is rather limited. Just recently I got involved in the discussion about the origins of modern humans and Neanderthals. I have read some seminal papers in the field as Krings et al., 1997, Krings et al., 1999, Ovchinnikov et al., 2000 to get some arguments but I had some difficulties in data interpretation in these articles.
My opponent says that if human and neanderthal sequences differ in around 35 positions and human (and diverge at 500 000 ya) and chimpanzee in around 60 postions (Krings, 1997 gave 55, Krings 1999, gave 93) then if we take the substitution rate the same for these comparisons (because human/chimpanzee divergence served as calibration point) the time for human/chimpanzee divergence will be in the range of 1,5 million years, which is senseless. I know that something is wrong in this logic, because Krings, 1999 gave the neanderthal/chimp difference as 94 bp. But I cannot reproduce simple and understandable way of calculation of species divergence age. I think that not all information was presented in papers because it is regarded as a basics for evolutionary biology. I have rather poor background in the field of evolution rates quantitation.
Can you, please, help me to produce the understandable and simple interpretation of the data in the papers, i.e. how to convert the differences in the sequences to the evolutionary divergence age for human/human/, neanderthal/human, human/chimp, neanderthal/chimp? I tried myself the simple quantification based on Krings, 1999 (substitution rate - 0.94x10-7 per site per year per lineage) paper but I got quite strange results that do not correlate to the paper, so I presume that I did not understand methodology:
Humans/chimps = 2,9 mln ya
Neanderthals/chimps = 2,94 mln ya
Hum/Hum = 344 000 ya
Hum/Neand = 1 mln ya
I will be very grateful for any hints or help because this situation drives me crazy.
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