Mutation: how about dividing by two?

By Razib Khan | September 12, 2012 1:27 am

There’s been a mild debate in the literature about the human mutation rate recently. I assume it will reach some consensus within the next few  years, but until then Nature Reviews Genetics has published something which lays out the implications in precise fashion for a slower mutation rate. Revising the human mutation rate: implications for understanding human evolution:

The four key points may be summarized as follows. First, the divergence between modern humans and both Neanderthals and Denisovans, which was originally estimated to be 272,000–435,000 years ago, is revised to 400,000–600,000 years ago. This is in better agreement with the range of estimated split times from mtDNA and also with the idea that the ancestral population of these groups may have been H. heidelbergensis. Second, for the split between the Khoe–San and other modern humans, revised estimates from nuclear genomic data suggest a divergence 250,000–300,000 years ago, older than single-locus estimates for the root of the human tree. Third, revised estimates of the separation time between Africans and non-Africans suggest that this predates the appearance of modern humans in Europe and Asia by up to 60,000 years. We have suggested a scenario of exodus from Africa via an intermediate population in East Africa and the Middle East, which may fit better with growing evidence for modern human occupation of the latter region before the wider colonization of Eurasia and may provide a longer interval for Neanderthal admixture with non-African populations. Finally, revised split times of 40,000–80,000 years ago for Europeans and Asians agree better with the palaeoanthropological record and with estimates from mtDNA.

The authors do understand that their phylogenetic model impacts their inferences. If there was a lot of archaic admixture into the Khoe and Bushmen their divergence from other modern humans might be inflated. But it is always striking to me that there is this strange result that populations like the Yoruba might be in a clade with non-Africans against Khoe and Bushmen.

CATEGORIZED UNDER: Genetics
MORE ABOUT: Genetics
  • http://forwhattheywereweare.blogspot.com/ Maju

    “… this strange result that populations like the Yoruba might be in a clade with non-Africans against Khoe and Bushmen”.

    But that’s normal: Bushmen (Khoisan in general) diverged first (clade mtDNA L0), then Pygmies and some elements in West Africans (clade mtDNA L1) and you still have Yorubas and most other Africans together with Eurasians-plus. Even some admixture can’t mask the depth of these fundamental divisions prior to the OoA.

  • DKshadow

    “the next fear years”. Freudian slip? You know something about the future that we don’t?

  • https://plus.google.com/109962494182694679780/posts Razib Khan

    #2, no, just really tired.

  • Tim

    How much does this push back the the human-chimp divergence from the last common ancestor?

  • NickMatzke

    I think the “clade” concept doesn’t apply here at all. Individual markers form clades (e.g. mtDNA phylogeny) but in humans you’d have a huge snaggle across many markers. But otherwise interesting stuff.

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This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

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