Out of Africa

From: glenn morton (mortongr@flash.net)
Date: Sun Feb 13 2000 - 11:14:24 EST

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    Due to my move last year and the mess up it caused in me receiving my
    journals via the mails, I am just now getting the August 1999 Scientific
    American. There is a fascinating article on the Out of
    Africa/multiregionalism controversy entitled "Is Out of Africa Going Out
    the door?" My interest in this concerns the growing evidence that there is
    some genetic input from the archaic hominids into modern mankind. And if
    they are our forefathers and mothers, then apologetically, we can't exclude
    them from Adam's race. And contrary to the widespread preference so
    recently expressed by David Siemens, that he "cannot push Adam and Noah
    back millions of years." (2/10/00), their genetic continuity and
    interbreeding with modern men makes it very difficult NOT to push Adam and
    Noah back millions of years!
     A couple of definitions of the out of Africa and multiregionalism are needed.

    First the multiregionalism (sometimes called candelabra) as proposed in the
    50s and 60s by Carleton Coon has been totally rejected by modern
    anthropology. In that view, each local variety of homo sapiens evolved
    independently from the local variety of archaic hominid. Modern views of
    multiregionalism place tremendous emphasis upon gene flow across all
    populations. Thus there was no independence to the evolution of the entire
    population as a whole. This modification of the old multiregional view
    allows each local population to be a mixture of local archaics and invading
    Africans. It is akin to Gunter Brauer's Hybridize and Replacement theory.
    (see Gunter Brauer, "The Evolution of Modern Humans: a Comparison of the
    African and non-African Evidence," in Paul C. Mellars and Chris B. Stringer
    ed. The Human Revolution. (Princeton: Princeton University Press, 1989),
    pp. 123-153, p. 124) Thus, multiregionalism no longer means what it did in
    the 60s when it garnered a very bad name for itself.

    The Out of Africa theory is claimed to refute any gene flow from the
    archaics to modern Homo sapiens. It is often claimed and thought by
    non-anthropologists that the Africans came out of Africa and totally
    replaced everyone with no interbreeding. This has not been the case with
    the majority of anthropologists who advocate Out of Africa. Stringer,
    Gamble and Tudge, who are Out of Africa proponents believe that there has
    been some gene flow between us and the archaics. A sampling of
    anthropological opinion follows:

    "As we have already mentioned, there are occasional hints of interbreeding
    between the two populations of hominids e.g., the bulging occipital bone of
    one of the Cro-Magnon skulls, or the projecting mid-face of one of the
    Moderns from Predmosti. We are not sure that such features do in fact
    represent the result of interbreeding, but even assuming that they do, we
    believe that such instances were exceptions, and that there was minimal
    gene flow (interbreeding0 between the two populations." Christopher
    Stringer and Clive Gamble, In Search of the Neanderthals, (New York: Thames
    and Hudson, 1993), p. 193
    "Economic competition for the available resources would be the mechanism of
    replacement of one population by another where there was coexistence,
    perhaps coupled in some areas with a small degree of interbreeding (in
    which e.g. a few Neanderthal genes would have been taken into the much
    larger modern human gene pool)." Christopher Stringer and Clive Gamble, In
    Search of the Neanderthals, (New York: Thames and Hudson, 1993), p. 72
            "The point is, though, that such breeding plans have given rise to a large
    body of genetics theory--and this theory shows that the British and
    European populations of Siberian tigers would effectively be genetically
    continuous even if the flow of genes between them was remarkably small. In
    other words, if just one European tiger per generation was brought to
    Britain--or indeed just one in several generations--this would achieve all
    the mixing required.
            "Translate this into the experience of early hominids, from erectus
    onwards: highly mobile, often adventurous, and marauding throughout Africa
    and Eurasia. It seems inconceivable to me that newly arriving groups would
    not have mated at least from time to time with peoples they met along the
    way. Sometimes the contacts would have been friendly, sometimes forced.
    But such things must surely have occurred, and if they did then there would
    indeed have been gene flow between the many groups, precisely in the way
    that Milford Wolpoff emphasizes. I still think the candelabra hypothesis is
    wrong. But I also feel that we can reasonably impose considerable gene flow
    on to the Out of Africa scenario. So in important details Wolpoff would
    certainly be right. Modern human beings would indeed contain Neanderthal
    genes." Colin Tudge, The Day Before Yesterday, (London: Pimlico, 1994), p. 237
    "The process of biological replacement was far more complex than mere
    population movements, and probably involved slow assimilation and
    hybridization of Neanderthal populations." Brian M. Fagan, The Journey from
    Eden, (New York: Thames and Hudson, 1990), p. 49.

    Now, given that background the article first attacks the issue of whether
    or not mitochondrial DNA really proves what it is so often asserted, that
    mankind is no older than 200,000 years and that there is no interbreeding.
    Wong writes:

            "The DNA from mitochondria, the cell's energy-producing organelles, has
    been key Out of Africa evidence. Mitochondria are maternally inherited, so
    genetic variation arises largely from mutation alone. And because mutations
    have generally been though to occur randomly and to accumulate at a
    constant rate, the date for the common mitochondrial DNA (mtDNA) ancestor
    can theoretically be calculated. This 'molecular clock' indicates that the
    mtDNA ancestor lived a mere 200,000 years ago, and the root of the gene
    tree traces to Africa. These results, along with the observation that
    variation is highest in Africa (indicating that modern humans had been in
    Africa the longest), seemed to offer unambiguous support to a recent
    African origin for all modern humans.
            "But the significance of each finding has been questioned. The date is
    suspect because he molecular clock depends on problematic assumptions, such
    as the calibration date and as some studies suggest, then the rate of
    mutation accumulation may have differed at different times. The African
    root for the mtDNA gene tree is compatible with Out of Africa, but it does
    not exclude Multiregionalism, which predicts that the common ancestor lived
    somewhere in the Old World, probably Africa. And neither does the high
    mtDNA variation in African populations as compared with non-Africans
    uniquely support Out of Africa, according to anthropologist John H.
    Relethford of the State University of New York College at Oneonta. 'You
    could ge t the same result if Africa just had more people living there,
    which makes sense ecologically,' he asserts." Kate Wong, 'Is Out of Africa
    Going Out the Door?" Scientific American, Aug. 1999, p. 13-14

    Wong quotes Alan Templeton, a leading geneticist as saying:

    "Very few people try to look across all the systems to see the pattern," he
    observes. Some nuclear genes indicate that archaic Asian populations
    contributed to the modern human gene pool, and Templeton's own analyses of
    multiple genetic systems reveal the genetic exchange between populations
    predicted by Multiregionalism."

    Templeton's technical work in this regard can be found at: Alan R.
    Templeton, "Human Races: A Genetic and Evolutionary Perspective," American
    Anthropologist, 100(1999):3:632-650.

    Templeton in that work challenges the idea that mtDNA diversity can be
    equated to age. Here is what he says and it is quite interesting:

    "The danger of using diversity levels as an indicator of population age
    from a bottleneck is illustrated by the observation that mitochondrial DNA
    diversity within Africa is higher in food-producing populations than in
    hunter-gatherers. By equating diversity to age, this result would imply
    that agricultural peoples in Africa represent the ancestral populations,
    whereas the hunter-gatherers are the recent descendant populations. Such a
    conclusion is not credible, and the diversity levels within Africa are
    interpreted as reflecting effective size differences." Alan R. Templeton,
    "Human Races: A Genetic and Evolutionary Perspective," American
    Anthropologist, 100(1999):3:632-650,, p.637

    After discussing the mtDNA evidence, Wong then discusses the evidence from
    the bones. Wong writes:

             "But those who believe that Out of Africa's genetic fortress is
    crumbling find confirmation in fresh fossil data that pose new difficulties
    for the theory's bony underpinnings. Last December researchers unearthed in
    western Portugal's Lapedo Valley a fossil that preserves in exquisite
    detail the skeleton of a four-year-old child buried some 24,000 years ago.
    According to Erik Trinkaus, a Washington University paleoanthropologist who
    examined the specimen, the team fully expected the remains to represent a
    modern human, based on its date and the style of the burial. But subsequent
    analysis, published in the June 22 Proceedings of the National Academy of
    Sciences USA, revealed a surprising combination of features, such as a
    modern-looking chin and Neanderthal limb proportions. After reviewing
    scientific literature on primate hybrids, Trinkaus concluded that this
    child resulted from interbreeding between Neanderthals and modern humans."
             "Not everyone is persuaded. Christopher B. Stringer of London's
    Natural History Museum, lead proponent of the Out of Africa model, wonders
    whether the fossil might simply represent a cold-adapted modern human,
    because Portugal then was colder than it is today. In any case, Stringer
    maintains that his model does not exclude occasional interbreeding." Kate
    Wong, 'Is Out of Africa Going Out the Door?" Scientific American, Aug.
    1999, p. 14

    And given the new dating of the Mungo remains, which I reported on last
    year, Wong relates:

             "Multiregionalism also best explains the surprising new date for a
    previously known fossil from western New South Wales, according to
    paleoanthropologist Alan Thorne of the Australian National University. In
    the June Journal of Human Evolution Thorne and his colleagues report that
    the fossil, known as Lake Mungo 3, now looks to be some 60,000 years
    old--nearly twice as old as previously thought--and unlike the other early
    Australian remains (all of which date to less than 20,000 years ago), this
    one bears delicate, modern features. To Stringer, this gracile form
    indicates the arrival of modern humans from Africa, albeit an early one.
    Over time, he reasons, selection could have led to the robust morphology
    seen 40,000 years later."
             "But Thorne argues that such dramatic change is unlikely over such
    a short period and that fossils from the only environmentally comparable
    region--southern Africa--show that people have remained gracile over the
    past 100,000 years. Moreover, Thorne maintains, "there is nothing in the
    evidence from Australia which says Africa"--not even the Mungo fossil's
    modern features, which he believes look much more like those of
    contemporaneous Chinese fossils. And Thorne observes that living indigenous
    Australians share a special suite of skeletal and dental features with
    humans who inhabited Indonesia at least 100,000 years ago."
             "Therefore, he offers, a simpler explanation is that the two
    populations arrived in Australia at different times--one from China and the
    other from Indonesia--and mixed, much like what has been proposed for
    Neanderthals and moderns in Europe. " Kate Wong, 'Is Out of Africa Going
    Out the Door?" Scientific American, Aug. 1999, p. 14

    The entire article can be found at:



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