I believe that 13M years here is sequence divergence counting both sides of the phylogeny, so 6.5Mya common chimp-human ancestor of average genetic locus. note pop split assumed is then younger. cc @FabriMafe
Also, hidden with Fig 4 in #Neanderthal x #Denisovan paper is the comment that ages are based on a human-chimp divergence of 13 mill. yrs. Any comments @razibkhan @aylwyn_scally @loronet @pontus_skoglund @MatejaHajdi @jjhublin @johnhawks ?https://twitter.com/ChrisStringer65/status/1032313206847492097 …
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A more ancient chimp speciation and thus longer time scale would accommodate Sima de los Huesos more easily on the Neandertal branch. My personal hunch would be that the tension between the split times and the Sima dating is mainly due to <100% continuity from Sima to Neandertals
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Or to a dating of Sima somewhat overestimate?
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The Sima sample looks so Neanderthal, dentally, that making it younger would fit better with some other data, but that would require new dating to overturn the prevailing scenario...
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Does anyone think about putting both sequence data and morphological change (as much as possible for both) in one tree and do Bayesian intference on the split times?
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A similar approach was tried to predict the age of Homo naledi, turned out to be a million years off. Morphology just not clocklike at the scale required.
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Retaining a primitive anatomy for a million years is one thing, developing a derived Neanderthal dental anatomy well ahead of other known fossils e.g. Pontnewydd, Krapina is another....
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Jebel Irhoud seems to have developed aspects of derived modern morphology well ahead of other known African samples.
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13 Mya is presumably human-chimp sequence divergence time, not speciation time (which is uncertain & can't be used as calibration). Haven't read paper yet. However I think it's using the present-day human mutn rate & thus probably too old, given recent slowdown in humans.
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So yes, have just looked at paper. they say they calibrated based on '13 Mya human-chimp divergence'. That's an estimate of the mean age of the human-chimp genetic common ancestor using the present-day human mutn rate. In other words it's equivalent to using the present-day rate.
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I think that's probably fine. There does seem to have been a slowdown on the human branch but perhaps not so much within the last few hundred kyr, and it seems not at all within last 50 kyr. So these dates seem reasonable to me.
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I discussed this in https://www.biorxiv.org/node/16868.full and argued we are justified in using the present-day human mutation rate for ancient DNA studies.
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Some of the authors on the hybrid paper worked on another back in 2012 that re-estimated the divergence to that time based on updated chimp generation/mutation rates. Maybe that's where they're getting this from.http://www.pnas.org/content/109/39/15716 …
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Human-chimp divergence of 12.1 million years is the conclusion of this paper. Moorjani, et al (2016). "Variation in the molecular clock of primates". Proceedings of the National Academy of Sciences. 113 (38): 10607–10612. doi:10.1073/pnas.1600374113.
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Interesting article. In a previous Lewis Research Unit paper (available on our website) we too put forward the divergence date at 13 mys. Nice to be collaborated finally.
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13 mys because... 1) bipedality implies exclusive human ancestry 2) genetic clock is always << mutation rate and we know both exactly 3) monkeys originated in the K 4) 6 or 4.15 mys chimp/gorilla ghost lineages for aren't enough (vs only a zillion human relatives)
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Gulls. Ring species. Go figure.
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Those of you relying on mutation rate = genetic clock, as per Kimura(68,91 etc) King, Jukes (e.g. K&J 68) and of course Haldane (57) (the latter is complete rubbish) are in for a big surprise.
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Denisova - a Stone Age lovenest?
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