Out of Africa

Jones Maxime Murphy morphy at cco.caltech.edu
Mon Nov 18 14:53:25 EST 1991


lamoran at gpu.utcs.utoronto.ca (L.A. Moran) writes:


>I thought that the recent Scientific American article by Cavalli-Sforza (1)
>was very sloppy and it grossly overstated the case for the Out-of-Africa 
>hypothesis of the origin of modern humans.

This statement is inexplicable, based on my reading of the very same article.

> I have no reason to reject this 
>hypothesis

Ah, those famous words! Have you read Stephen J. Gould's "The Mismeasurement of
Man"?

> but I was prompted to re-examine the original data to see how
>strongly it supports the idea that modern humans arose in Africa and spread
>out from there replacing Neanderthal (and others). This re-examination has 
>led me to conclude that many scientists, particularly geneticists and 
>molecular biologists, are guilty of unwarrented assumptions concerning 
>human evolution. I think that we should be more cautious accepting the
>Out-of-Africa hypothesis.

Are you kidding? Non-African scientists have strenously resisted the notion of
an African genesis of Man. It is simply the crushing preponderance of the
evidence that has overcome the overabundance of "caution"(negrophobia) that
characterized research on human origins.

>     "An African origin for Homo sapiens sapiens is supported by an
>      abundance of archaeological, linguistic, and genetic evidence,
>      including the use of the chimpanzee to root the human genealogical
>      tree."

>I don't believe that this statement is correct for the resons that are listed
>below. Can anyone enlighten me?

By all means.

>Archaeological evidence: It is my understanding that anthropologists and
>   archaeologists are deeply split on this issue. Although most will agree
>   that the genus Homo arose in Africa (that's where the earliest fossils
>   are) they do not agree that MODERN man originated in Africa and spread
>   out from there replacing the indigenous populations.

I just attended a talk by Niles Eldredge at the American Museum of Natural
History. He emphatically stated that by far the earliest anatomically modern
human remains are only to be found in Africa. He defined anatomically modern
basically as gracile(tall, slender) and lacking in brow ridges.

> There seems to be
>   good evidence that Homo has been present in Eurasia and Africa for over
>   one million years and that the transformation to modern Homo sapiens
>   sapiens occurred simultaneously in many parts of the world.

There is no evidence to support this theory. This is simply racist wishful
thinking posing as "science", an all too frequent occurrence in the study of
human origins.

> My readings
>   indicate that some anthropologists claim that the earliest examples of
>   Homo sapiens sapiens can be found in South Africa and these date to about
>   125 thousand years ago. These claims are disputed on several grounds.
>   Is my understanding correct?

Yes, the claims are disputed. The grounds for the dispute have never been 
more flimsy than they are today, with the recent improvements in genetic
analysis.

>Linguistic evidence: I am not aware of ANY linguistic evidence that supports
>   the Out-of-Africa theory. As far as I can tell the linguistic data
>   suggests that many Eurasians share a common linguistic background and 
>   that it may be possible to incorporate some other languages into a larger
>   superfamily of languages. As far as I am aware it has not been possible 
>   to conclude that ALL modern languages are descended from a single ancestral
>   language and it certainly has not been possible to deduce where these
>   original (mythical) ancestors lived. The correlation between language
>   and genetics that is being pushed by Cavelli-Sforza (5) seems to me to be
>   mostly trivial.

That is a value judgement about a rock-solid conclusion that you appear to find
unappetizing. It has no net semantic content and is therefore itself trivial.

The C-S article does not address the question of monogenesis or polygenesis of
language *at all*! It merely points out the correlation of language families
as they now exist with the reconstructed "family tree" obtained from 
mitochondrial DNA. Such a correlation, coming from vastly different aspects
of humanity, is hardly trivial, in my opinion.

> It is the exceptions that are interesting. I note that
>   Cavelli-Sforza believes that it is the acquisition of language that 
>   provided modern humans with the advantage necessary to exterminate other
>   humans such as Neanderthal (5). Does anyone want to defend the idea that a 
>   study of modern languages supports an African origin of Homo sapiens 
>   sapiens?

No. It neither supports nor contradicts it. It merely correlates very closely
and impressively with the results obtained from a large survey of DNA. It is 
those results which support afrogenesis.

>Genetic evidence: A lot of genetic "evidence" seem to me to be highly suspect.
>   It relies more heavily on imagination and unproven assumptions than on
>   real science.

This is interesting. I'm a physicist. I see real science here. Who are you and
what is your claim to decide for the rest of us what is "real science"?

> An exception is Wilson's original work on mitochondrial
>   DNA polymorphisms and Cavelli-Sforza's data on nuclear genes. However,
>   this data can be interpreted in two ways (IMHO). The data indicates that 
>   the earliest split in the evolution of modern humans  gave rise to two 
>   main groups whose descendents now live in Africa on the one hand and 
>   Eurasia on the other. What is the genetic evidence that the ancestors of 
>   these two groups lived in Africa as opposed to Asia (or even Antarctica, 
>   for that matter)? Isn't the data just as consistent with an Asian origin 
>   of modern man and subsequent migration of the first sub-population to 
>   Africa rather than vice versa?

Your reading comprehension has clearly failed you. Reread that article. The
central point of the article was just the negative reply to your last 
question!!

The genetic base of Eurasia is narrower than that of Africa. Dramatically so.
This is particularly striking considering the relative area and populations of
these landmasses.

I strongly urge you to reread the article. Your prejudices have clearly
rendered your (no doubt keen) analytical powers impotent.
rendered your rational powers impotent.

>   Cavelli-Sforza (1) says,

>          "Our first result supports a conclusion that has emerged
>           from studies of human physical anad cultural remains: an
>           African origin of our species. We found that the genetic 
>           distances between Africans and non-Africans exceed those 
>           found in other intercontinental comparisons. This result 
>           is exactly what one would expect if the African separation 
>           was the first and oldest in the human family tree."

The key point here is that Africans are uniquely distant from *all* others. You
naturally neglect to point out that intra-continental genetic distances in
Africa are themselves comparable to intercontinental distances for all others,
a significant fact.

>   As far as I can see the results may be consistant with the Out-of-Africa
>   hypothesis but they are also consistant with an Out-of-Eurasia hypothesis.

How so? How would you "rationalize" an Out-of-Eurasia scenario given the data?

>   In a more scientific paper (6) Cavelli-Sforza's group doesn't even
>   mention the Out-of-Africa hypothesis but instead they point out that
>   Europeans are a genetic mixture of African and Asian populations
>   and that the people who replaced Neanderthal in Europe probably
>   originated in West Asia. These West Asians "...may have already been
>   a mixture between Africans and East Asians, because West Asia is
>   geographically intermediate between Africa and East Asia." Is this
>   an argument for two independent origins of modern man (Africa and
>   East Asia)? Or is it leading up to a defense of the idea that modern
>   man may have evolved from widespread indigenous populations?

You speciously refer to a three year old paper, written before the latest
analysis was completed. This is simply a dishonest attempt to portray the views
in the above paragraph as being contemporaneous with the latest issue of Sci-Am.

>   In the original paper (3) Wilson's group makes a special point of the
>   fact that the Eurasian group of mitochondrial DNA sequences also 
>   includes some populations that now live in Africa. They conclude that 
>   Africa is the "..likely source of the human mitochondrial gene pool..." 
>   because this assumption "...minimize(s) the number of intercontinental 
>   migrations needed to account for the geographical distribution of
>   mtDNA types." I don't believe that the number of required migrations
>   is any different if one assumes a Eurasian origin so that the logic of 
>   this statement is questionable.

This last statement is incredible. Can you offer a eurogenetic scenario which
would result in an Africa with a far greater genetic diversity than Eurasia?
Why should we bend over backwards to grasp this scenario, given that the data
far more readily supports afrogenesis?

>   Incidently, Cavalli-Sforza describes Wilson's results as follows;

>        "...the Wilson group derived a tree of descent that showed 
>         more differentiation in Africa than anywhere else. That
>         finding indicated that human mitochondrial DNA had been
>         evolving for the longest time in Africa - that is, it can
>         be traced to a single African woman."

>    Strictly speaking what Wilson's group showed was that there was more
>    "differentiation" (ie. sequence divergence) among Black Americans than
>    among other identifiable human populations. They assumed that all mtDNA
>    sequences present in Black Americans could be traced to an African
>    origin in spite of the fact that several of these individual sequences
>    clustered with European and/or Asian mtDNA types. The mitochondrial
>    DNA lineages do not make a lot of sense - there are too many unexplained
>    anomolies. See also ref (4). 

This is not the case with the study reported by the Sci-Am article, though. For
this study, a variety of peoples around the world were sampled. What do you have
to say about that study? Why focus your attentions on the outdated Wilson study?

>Rooting the tree: One could also use orangutans to root the human geneological
>   tree but this would not be considered evidence that humans originated
>   in Indonesia! I assume that the authors meant to say that the closest
>   living ancestors of humans are chimps (and/or gorillas) and that these
>   species also live in Africa. But this is evidence in favor of the African
>   origin of the GENUS Homo and not of the SPECIES Homo sapiens sapiens.
>   Am I confused about this? (Does anyone know if the fossil evidence of
>   chimp and gorilla evolution confirms that these species are confined to
>   Africa?)

I have heard of no evidence of chimps or gorillas outside of Africa. Chimps are
particularly important, since they're our closest living relatives(and NOT
ancestors!!!). It is unfortunate that some continue to rank-order existing
animals as if nature as it exists today is merely an evolutionary ladder
leading up to homo sapiens. This is absurd.

>Laurence A. Moran (Larry)
>Dept. of Biochemistry
>University of Toronto

Let's face it, Larry. Inside of you there's a nigger, dying to get out.
Jones
-- 
:)



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