From: Glenn Morton (glennmorton@entouch.net)
Date: Tue Jun 17 2003 - 15:58:59 EDT
I have long argued that there is good, indisputable evidence for genes from
Neanderthals and other ancient hominids in the genomes of modern
populations, see http://www.glenn.morton.btinternet.co.uk/hegene.htm
This view is not the darling of the press, and is objected to by many
christians who want to have Adam and Eve associated with the mitochondrial
Eve of genetics. This Eve lived somewhere between 0 and 800,000 years ago
but the most likely time frame is 100-200 kyr ago. This gives the old earth
creationists a place to neatly fit Eve into the fold. Several authors take
this approach. David Wilcox believes this and says so in his PSCF article
"Both cultural and physical evidence suggests an abrupt establishment of the
image about 100,000 years ago." ~ David L. Wilcox, "Adam, Where Are You?
Changing Paradigms in Paleoanthropology," Perspectives on Science and
Christian Faith , 48:2( June 1996), p. 94
Robert Newman takes this position, specifically citing the mtDNA evidence as
being indicative of the origin of humanity:
ìOne Christian, Glenn Morton, puts the origin of the human race back several
million years ago with the Australopithicines; at the other extreme is Dick
Fischer, who places the origin of humans about five thousand years ago with
Adam, but not as the progenitor of the entire human race. I am closer to
Hugh Ross, who sees the creation of Adam as some tens of thousands of years
ago, which seems to fit the evidence from mitochondrial Eve and Y-chromosome
Adam better than Mortonís view, and the biblical teaching of Adam as our
forefather better than Fischerís. I am closest to the position of John
Bloom.î Robert C. Newman, ìConclusionî in J. P. Moreland and John Mark
Reynolds, editors, Three Views on Creation and Evolution, (Grand Rapids:
Zondervan, 1999), p. 154-155
Hugh Ross twists the mitochondrial Eve to fit his preconceived idea of Adam
and Eve being no older than 60,000 years (Hugh Ross, "Chromosome Study Stuns
Evolutionists," Facts & Faith, 9:3,(1995) p. 3). There simply is not way
that one can fit the genetics of humanity in to the past 60,000 years. All
these efforts forget that the history of one gene system is not the history
of the population. If it were, then every single gene system analyzed would
yield the same age. They don't.
As mentioned above, the studies show a wide range of time frames for which
mitochondrial Eve and Y-chromosome Adam could have lived. Clark writes:
ìThis research produces estimates of the age of the most
recent human mtDNA
ancestor that range from 0 to 806,000 years (95% confidence interval, data
from 12 studies postdating 1991). Coalescence estimates of modern human
ancestry based on Y-chromosome and nDNA polymorphism data (11 studies
postdating 1993) range from 62,000 to 1,300,000 years. " G. A. Clark,
ìComments,î Vinayak Eswaran, ìA Diffusion Wave Out of Africa,î Current
Anthropology, 43(2002):5:749-774, p. 765
Obviously, this doesn't fit the preconceptions of those authors above all of
whom prefer a younger Adam and Eve. But the data I present on my page
http://www.glenn.morton.btinternet.co.uk/hegene.htm has gene systems which
are considerable older than even this. The age is calculated for these
systems by the length of time it would take for the alleles to accumulate
the number of mutations which are observed. Young genes have few mutations
and old genetic systems have lots of mutations.
But in spite of this evidence, the Out of Africa viewpoint has dominated
anthropology. This is the theory that modern humans arose in Africa and
replaced all the archaic populations around the world. They cite the mtDNA
data as support for their view, claiming that there is no way that
multiregionalism (the view that there was interbreeding between the archaics
and the modern humans) can explain the features seen in modern humans.
These are, low genetic diversity in most gene systems, low effective
populations and indications of a population bottleneck at some places in the
genome.
Now, Vinayak Eswaran writing in Current Anthropology (Dec 2002 pp 749-774)
presents a numerical model of a selectively advantageous multi-gene system
which moves out in a wave across the land spreading the advantageous genes
without having any migration.
Eswaran writes:
ìThis 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.î
Vinayak Eswaran, ìA Diffusion Wave Out of Africa,î Current Anthropology,
43(2002):5:749-774, p. 749
and
ìIn this paper I suggest that most of the features associated with
anatomical modernity evolved in Africa as a coadapted gene combination (or
ìgenotypeî) and spread across the world because they collectively offered
some strong selective advantage. The development of such a genotype can
quite plausibly be based on the shifting-balance theory of Sewall Wright
(1932). Wrightís theory suggests that, in populations subdivided into small
semi-isolated demes, evolution can occur in the following three phases: (1)
Genetic drift propels different demes along different trajectories,
facilitating an exploration of the adaptive landscape available to the
species. (2) Intrademe selection allows some demes to reach a new and higher
adaptive peak. (3) Interdeme selection propagates the gene combinations that
correspond to these adaptive advances and shifts the entire species to the
new peak. For all this to occur, the demes are required to be (a) small
enough to allow significant genetic drift and (b) semi-isolated, to
facilitate the formation of complex coadapted gene combinations that would
otherwise be broken up by admixture.î Vinayak Eswaran, ìA Diffusion Wave Out
of Africa,î Current Anthropology, 43(2002):5:749-774, p. 750
and
ìIt is proposed below that the modern morphology may itself
have given the
advantage, possibly due to lowered childbirth mortality, that propagated
anatomical modernity.î Vinayak Eswaran, ìA Diffusion Wave Out of Africa,î
Current Anthropology, 43(2002):5:749-774, p.751
and
ìThis theory thus suggests, in contrast to the recent
African-origin model,
that the emergence of modern humans was not a speciation but an intraspecies
ìcharacter changeî (Wright 1982).î Vinayak Eswaran, ìA Diffusion Wave Out of
Africa,î Current Anthropology, 43(2002):5:749-774, p. 751
He suggests that childbirth mortality was reduced by the modern form but
that is a controversial suggestion. The important thing is that anything
that gave a selective advantage could spread the modernity genes. He
describes the way the diffusion wave works:
ìEthnographic studies of present-day hunter-gatherers suggest an
interbreeding rate of around 0.05. This value of mo with an assumed
a=0.07/generation would allow a diffusion wave of modernity to spread at a
rate compatible with the fossil recordótraveling a distance of 11,000 km or
so in 4,000 generations. Recall that a is the relative growth rate in a
generation of, say, 20 years.î Vinayak Eswaran, ìA Diffusion Wave Out of
Africa,î Current Anthropology, 43(2002):5:749-774, p. 755
and
ìThe simulations show the wave front to be barely 800 km in width, and the
region within which clear signs of hybridization would have appeared could
have been as narrow as 300 km. Hybrids ahead of this narrow region were
close to archaic, while those behind were essentially modern. Thus if the
diffusion wave traveled through 3,000 km of Europe between 45,000 and 25,000
years ago, only 10% of the fossils of that period could be expected to have
clearly mixed morphologyówhich may explain the rarity of obvious hybrids in
the fossil record.î
ìAnother empirical observation that could be explained by
these simulations
is the relatively rapid transition that has been recorded to occur at the
local level. The transition from ëprogressiveí archaic to ëessentiallyí
modern could have taken as little as 2,000 to 3,000 years, the time required
for the 300-km core of the wave front to pass over a site.î Vinayak Eswaran,
ìA Diffusion Wave Out of Africa,î Current Anthropology, 43(2002):5:749-774,
p.757
Note that in this model, there is no replacement, merely a character change.
There is interbreeding which explains the genes listed on my web page,
explains the fact that the red-headed gene seems to have been inherited in
modern European populations from the Neanderthals (see
http://www.calvin.edu/archive/asa/200201/0288.html). The theory also
explains why there is such a low genetic diversity in humans compared with
most other species.
ìThe wave-front bottlenecks and the consequent homogenization
could explain
why genetic diversity is low in human populations, as are the apparent
coalescence times for some loci [particularly in mtDNA and Y-chromosome
studies], and why so small a number as around 10,000 individuals has been
estimated by many geneticists as the effective size of the modern human
lineage. The diffusion-wave theory thus offers an alternate explanation for
these empirical observations that have generally been interpreted as support
for the recent-African origin replacement model.î Vinayak Eswaran, ìA
Diffusion Wave Out of Africa,î Current Anthropology, 43(2002):5:749-774,
p.759-760
(I must note that this low diversity can't be due to a recent origin of
humanity so long as there are genetic systems which would have taken
millions of years to generate the observed number of alleles in humanity.
One such system is the Major Histocompatibility Complex (MHC) which shows no
population bottleneck for tens of millions of years)
and
ìThe genetic diversity of present-day Africans at neutral DNA loci has
usually been found to be higher than in all other populations. This is
usually seen as support for the recent-African-origin model. However, in the
present theory, the same empirical observation is expected from the core
region, where the modern genotype first evolved and modern humans have the
deepest roots.î Vinayak Eswaran, ìA Diffusion Wave Out of Africa,î Current
Anthropology, 43(2002):5:749-774, p. 760
But would the 'bottleneck' phenomenon preclude the high-diversity ancient
genes? No. Eswaran says:
ìIt is already been argued above that unique African neutral
alleles being
carried by the diffusion wave front would have developed the typical
symptoms of bottlenecked populations, leading to significant allele loss.
However, with ancient and widespread polyporphisms there would also have
been the possibility of allele replenishment through assimilation from
archaic populations, for the same polymorphisms, so to speak, would have
been found in both modern and archaic humans.î Vinayak Eswaran, ìA Diffusion
Wave Out of Africa,î Current Anthropology, 43(2002):5:749-774, p. 761
One thing I really like about Current Anthropology is that there are always
reviewers to tell you what is wrong the the theory immediately. The
reviewers criticized Eswaran's suggestion thatpelvis shape change was the
reason for decreased infant mortality. They criticised him for appearing to
think that his wave was the only process which occurred, but no one said his
theory wouldn't work. Harpending wrote:
ìThis paper will quickly become a central part of the canon
of biological
anthropology. Eswaran starts with a very simple model of the appearance of a
new advantageous trait complex in a subdivided populationóselective
advantage along with demic diffusionóand derives a rich variety of
consequences of the process. The simple model explains the available genetic
and morphological data better than anything we have had until now and gives
us many testable predictions.î Henry Harpending, ìComments,î Vinayak
Eswaran, ìA Diffusion Wave Out of Africa,î Current Anthropology,
43(2002):5:749-774, p. 765
Clark wrote:
ìAs a convinced multiregionalist, I like Eswaranís paper because it
proposes a plausible scenario to explain the appearance of modern form
without the necessity for invoking migration.î G. A. Clark, ìComments,î
Vinayak Eswaran, ìA Diffusion Wave Out of Africa,î Current Anthropology,
43(2002):5:749-774, p. 765
Rosenberg wrote:
ìEswaran offers an intriguing and sophisticated model for the causes of
morphological change in Upper Pleistocene human evolution and subsequent
modern genetic diversity.î Karen Rosenberg, ìComments,î Vinayak Eswaran, ìA
Diffusion Wave Out of Africa,î Current Anthropology, 43(2002):5:749-774, p.
766
Trinkaus wrote:
ìIn this elegant demonstration, Eswaran has done what has been needed for
some period of time, he has provided an explicit model with explicit
assumptions to model the populational and genetic processes by which modern
human biology may have spread and eventually become the dominant form across
the Old World.î Erik Trinkaus, ìComments,î Vinayak Eswaran, ìA Diffusion
Wave Out of Africa,î Current Anthropology, 43(2002):5:749-774, p. 767
and
ìI am convinced that the ëdiffusion-waveí model was a major player in a
number of regions and time periods during the process of modern human
emergence (which, after all, took more than 70,000 years to occur and
involved all of the inhabited Old Word), but I remain unconvinced that it
can explain all of the factors to which Eswaran applies it without too heavy
a dose of special pleading.î Erik Trinkaus, ìComments,î Vinayak Eswaran, ìA
Diffusion Wave Out of Africa,î Current Anthropology, 43(2002):5:749-774, p.
767
Wolpoff wrote:
ìStill, there is no question that in some form or other Eswaranís
diffusion-wave model is quite likely a valid explanation for the
multiregional pattern of any one of a number of specieswide events in human
evolutionary history. It is a significant and particularly insightful
description of how multiregional evolution might be expected to work when a
specieswide change involves a package of characteristics that have a single
origin but are related only by the common adaptation they promote.î Milford
H. Wolpoff, ìComments,î Vinayak Eswaran, ìA Diffusion Wave Out of Africa,î
Current Anthropology, 43(2002):5:749-774, p. 769
Zilhao writes:
ìI cannot but agree with these conclusions, since I have been
arguing along
similar lines." Joao Zilhao, ìComments,î Vinayak Eswaran, ìA Diffusion Wave
Out of Africa,î Current Anthropology, 43(2002):5:749-774, p. 769
Here at last is an explanation for how modernity arose which does not
require a break between the archaics and moderns. Indeed, it requires
genetic continuity and it explains the genetic data as one concise theory.
It doesn't have to ignore the data indicating ancient lineages in some gene
systems. Christian apologists should take note. They probably won't. It
seems they rarely do.
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