Additional comments on Eswaran's "diffusion wave" hypothesis.

[Jacques Cinq-Mars]

Again from Current Anthropology, a short paper that should be read by people who have developed an interest in Eswaran's "diffusion wave"  hypothesis.

Jacques Cinq-Mars

Pearson, Osbjorn M.  and Anne C. Stone. 2003. On the Diffusion-Wave Model for the Spread of Modern Humans. CA CA 44(4): 559-561.

Introductory statement:

Eswaran (CA 43:749–74) provides a demonstration of
how genes and morphological traits of archaic Eurasian
hominids could have existed in a fairly high frequency
in the earliest modern humans outside of Africa and yet
be virtually absent in living populations. He proposes
that several genes could have been responsible for a single
advantageous trait, such as the size of full-term fetus’s
face, that would have conferred a selective advantage
on individuals who possessed all of the required
alleles. His model predicts that the favorable alleles
would have increased gradually in frequency, eventually
reaching fixation. For the model to fit the available genetic
data, one must assume that all the genes linked
with the advantageous loci also increased in frequency,
eventually “modernizing” the entire nuclear genome.
Variation in neonatal facial size may not account for a
major selective advantage (Rosenberg 2002), but Eswaran’s
insight is applicable to any morphological trait
involving multiple loci and a strong selective advantage.
Although the diffusion-wave model initially seems
persuasive, we argue that it works only if the amount of
archaic admixture was very small. Four major difficulties
confront the model…

© 2003 by The Wenner-Gren Foundation for Anthropological Research. All rights reserved 0011-3204/2003/4404-0009$1.00

CLICK HERE

Reference to Eswaran's original paper:

Eswaran, Vinayak. 2002. A Diffusion Wave out of Africa. The Mechanism of the Modern Human Revolution? CA 43(5):749-774.

Abstract:

This paper proposes that the worldwide transition to an anatomically modern human form was caused by the diffusive spread from Africa of a genotype—a coadapted combination of novel genes—carrying a complex genetic advantage. It is suggested that the movement out of Africa was not a migration but a “diffusion wave”—a continuous expansion of modern populations by small random movements, hybridization, and natural selection favoring the modern genotype. It is proposed that the modern genotype arose in Africa by a shifting-balance process and spread because it was globally advantageous. It is shown that the genotype could have spread by directionally random demic diffusion, but only under conditions involving a low rate of interdeme admixture (“interbreeding”) and strong selection. This mechanism is investigated using a quantitative model that suggests explanations for many puzzling aspects of the genetic, fossil, and archaeological data on modern human origins. The data indicate significant genetic assimilation from archaic human populations into modern ones. A morphological advantage of the modern phenotype— possibly reducing childbirth mortality—is proposed as the cause of the transition. The evidence of this and previous human “revolutions” suggests that the shifting-balance process, proposed by Sewall Wright, was particularly important in human evolution —possibly because human populations had a small-deme social structure with low interbreeding rates that allowed it to operate. This may explain the relative uniqueness of human evolution.

© 2002 by The Wenner-Gren Foundation for Anthropological Research. All rights reserved 0011-3204/2002/4305-0003$3.00

For a PDF version of the full article, CLICK HERE.

[lagarvelho]

Jacques:

Apparently you have to have a paid subscription toi the journal to get accesss.  It keeps asking me for my password.
Anne G

[trehinp]

Just for info,

The French magasine "Siences Humaines", dated December 2005, features a full page news article on Eswaran's hypothesis.

A couple of new papers have also been published recently on this subject;

The human wave: people may have evolved fluidly, with lots of interbreeding
Science News,  August 6, 2005  by Bruce Bower. (Easier access here than through Science News website)

And a second 2005 article Here


Quite provocative articles... I thought that some of you might be interested...

Yours very friendly.

Paul

[Jacques Cinq-Mars]

Just for info,

The French magasine "Siences Humaines", dated December 2005, features a full page news article on Eswaran's hypothesis.

A couple of new papers have also been published recently on this subject;

The human wave: people may have evolved fluidly, with lots of interbreeding
Science News,  August 6, 2005  by Bruce Bower. (Easier access here than through Science News website)

And a second 2005 article Here


Quite provocative articles... I thought that some of you might be interested...

Yours very friendly.

Paul

Paul,

Thanks, but I couldn't get through to 'Sciences Humaines' and the URL for what you refer to as "a second [article] 2005" is not functional.

Jacques

[trehinp]

Jacques,

The article in "Sciences Humaine" is only available in paper form. I think that magazine is available in press shops in Montreal. It is not giving much information anyhow. Its main interest was to attract attention to Eswaran's research work which I didn't know about. I've seen that it had been a PALANTH topic by checking for his name before posting my message...

I have found the two article I am refering to through a Google research, my curiosity having been tickled by the  "Sciences Humaine" article.
 
The first link works fine for me . The second link I gave indeed doesn't work, sorry I must  have made a mistake while coding the URL short ref.

Here they are again but this time in their full lengthy html code
First article:
http://www.looksmartrecreation.com/p/articles/mi_m1200/is_6_168/ai_n15343164

Second article:
http://harpend.dsl.xmission.com/Documents/eswaran%20et%20al%202005%20genomics%20refutes%20exclusively%20african%20origin%20jhe.pdf

I hope this works now...

Paul

[Daryl Habel]

And a second 2005 article Here

The second url works now, but it appears Paul originally meant to send a URL leading to Henry Harpending's webpage containing a selection of documents:
CLICK HERE

(Added later as a modification.  I see the second URL has been modified later and now leads to Harpending's page as I post below)

Among these the sixth is a hyperlink to a pdf  to the pre-print  (it is not the CA paper itself) of Eswarans original paper "A Diffusion Wave Out of Africa".  But I believe Paul was referring to the seventh document in the list, shown as "eswaran et al 2005 g".  This is a hyperlink leading to  an "in press" article of the most recent publication, no longer "in press" but published as:

Eswaran, V., Harpending, H. & Rogers, A.R. (2005). Genomics refutes an exclusively African origin of humans. Journal of Human Evolution 49 (1): 1-18.

CLICK HERE

Abstract
Ten years ago, evidence from genetics gave strong support to the “recent African origin” view of the evolution of modern humans, which posits that Homo sapiens arose as a new species in Africa and subsequently spread, leading to the extinction of other archaic human species. Subsequent data from the nuclear genome not only fail to support this model, they do not support any simple model of human demographic history. In this paper, we study a process in which the modern human phenotype originates in Africa and then advances across the world by local demic diffusion, hybridization, and natural selection. While the multiregional model of human origins posits a number of independent single locus selective sweeps, and the “out of Africa” model posits a sweep of a new species, we study the intermediate case of a phenotypic sweep. Numerical simulations of this process replicate many of the seemingly contradictory features of the genetic data, and suggest that as much as 80% of nuclear loci have assimilated genetic material from non-African archaic humans.

Keywords: Modern human origins; Multiregional hypothesis; Out of Africa hypothesis; Phenotype sweep

I'm not sure whether announcement of  this paper was ever posted here, but for those interested and do not have access to JHE, Harpending's webpage provides a link to the "in press" version of this latest published article dealing with Eswaran's diffusion wave model .

Dar