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Natural Science Forum / Biology / Paleontology / January 2006Article: On early Human Dispersal from Africa
On early Human Dispersal from Africa The following points are made by R. Dennell and W. Roebroeks (Nature 2005 438:1099): 1) A key assumption in accounts of early hominin evolution is that the genus Homo originated in Africa, and an early form, classified either as Homo ergaster or H. erectus sensu lato, was the first to leave about 1.7-1.9 Myr ago (depending upon one's choice of dates and specimens), and then colonized southern Asia as far as 40 deg N. The identification of east Africa as the "core" area for the genus Homo (including H. ergaster) as well as tool-making seems secure to most palaeoanthropologists, and the most recent attempts at modelling early hominin dispersals start implicitly from the assumption that H. ergaster originated in east Africa and then dispersed across Asia. 2) In fact, the evidence that H. ergaster originated in east Africa is less convincing than it seems. H. ergaster marks such a radical departure from previous forms of Homo (such as H. habilis) in its height, reduced sexual dimorphism, long limbs, and modern body proportions that it is hard at present to identify its immediate ancestry in east Africa. Not for nothing has it been described as a hominin "without an ancestor, without a clear past". Full Text at ScienceWeek http://scienceweek.com/2006/sw060120-4.htm  SignaturePosted by Robert Karl Stonjek > On early Human Dispersal from Africa > [quoted text clipped - 24 lines] > has it been described as a hominin "without an ancestor, without a clear > past". "Reduced sexual dimorphism" - but how would they know? As far as I know no one has found a sufficiently complete early erectine female skeleton to estimate how tall they grew - certainly not one reasonably contemporaneous in time & space to the Turkana boy. I remember reading in Leakey's Origins Reconsidered of their surpirise at the height of the Turkana boy, because before that the mental picture (& it seems the prevailing assumption was no more than that) was of a short (shuffling? grunting?) human. Could it be that the assumption of low sexual dimorphism is also no more than that? Ross Macfarlane > Full Text at ScienceWeek > http://scienceweek.com/2006/sw060120-4.htm > > On early Human Dispersal from Africa > > [quoted text clipped - 29 lines] > estimate how tall they grew - certainly not one reasonably contemporaneous > in time & space to the Turkana boy. Oh, I wouldn't be so sure. There is the 1.7 Ma KNM-ER 1808, an adult female whose bones were distorted by a bone disease . I can't remember if they discussed her stature, but there's enough of the skeleton (see the illustration on page 193 of Walker & Shipman's "Wisdom of the Bones") to make an estimate. I'll have to do some re-reading about this. Dar > I remember reading in Leakey's Origins Reconsidered of their surpirise at > the height of the Turkana boy, because before that the mental picture (& it [quoted text clipped - 6 lines] > > Full Text at ScienceWeek > > http://scienceweek.com/2006/sw060120-4.htm [snip] >> > 2) In fact, the evidence that H. ergaster originated in east Africa >> > is [quoted text clipped - 27 lines] > this. > Dar Estimate statuture of KNM-ER 1808 is 173 cm (5' 8"). Anton SC(2003) Natural History of Homo erectus. Yrbk. Phys. Anthropol. 46: 126-170. http://www.nyu.edu/gsas/dept/anthro/programs/csho/anton.html >> I remember reading in Leakey's Origins Reconsidered of their >> surpirise at [quoted text clipped - 9 lines] >> > Full Text at ScienceWeek >> > http://scienceweek.com/2006/sw060120-4.htm > [snip] > [quoted text clipped - 36 lines] > > http://www.nyu.edu/gsas/dept/anthro/programs/csho/anton.html Thanks, that saved me some time looking for it. That's pretty tall for the time period. Given the estimates for KNM-ER 15000, I'd have to say that this is a good indication of reduced sexual dimorphism in African H. erectus/ergaster. Dar > >> I remember reading in Leakey's Origins Reconsidered of their > >> surpirise at [quoted text clipped - 9 lines] > >> > Full Text at ScienceWeek > >> > http://scienceweek.com/2006/sw060120-4.htm correction: KNM-WT 15000 ... > > Estimate statuture of KNM-ER 1808 is 173 cm (5' 8"). > > [quoted text clipped - 8 lines] > H. erectus/ergaster. > Dar Thanks gents, I bow to your greater knowledge... Ross Macfarlane > On early Human Dispersal from Africa > [quoted text clipped - 27 lines] > Full Text at ScienceWeek > http://scienceweek.com/2006/sw060120-4.htm Later erectus had less sexual dimorphism but I wouldn't bet three cents that this was true for ergaster. I've read a few articles that suggested that this change may have been on going for a long time. You also have some bleeping tiny finds most of which have been claimed to be females. > 2) In fact, the evidence that H. ergaster originated in east Africa is less > convincing than it seems. H. ergaster marks such a radical departure from [quoted text clipped - 3 lines] > has it been described as a hominin "without an ancestor, without a clear > past". >From what I've read, H. georgicus fit pretty squarely into the morphological gap between H. habilis and H. ergaster. Of course, it is not from East Africa. |
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