Re: [asa] Humanity and the Fall: Questions and a Survey

Dick,

Isn't the description you give here multi-regionalism? Not the
prevailing view at present. (Despite what Glenn says.) From the data
Rich summarized, if I understand it, the current human populations in
each of the locations you mention are much more recent.

Rich, can you clarify?

TG

On May 4, 2008, at 9:48 PM, Dick Fischer wrote:

> Hi Rich and Greg,
>
> I think you are complicating what could be a simple explanation.
> Let’s say you have a breeding population in Africa (Negroid) that
> formed pockets of isolated tribes and percolates for let’s say a
> few million years. A small group chased a herd of gazelles up north
> and took off for Europe say 150,000 years ago and evolved into
> Neanderthals. Another group took off about 100,000 years ago and
> split with one group (with Mongoloid features) heading eventually to
> China then Japan and across the Bearing Strait to populate the
> Americas. The other main group populated the Caucasus Mountains
> (Caucasians) and some migrated to Europe where they likely
> encountered Neanderthals. Presumably, the Neanderthal males were
> dispatched over time with the more attractive of the females
> contributing genetic material to the marauding Homo sapiens.
>
> One migration out of Africa went to Flores and became Hobbits,
> another wound-up as Aborigines in Australia. And I think that
> pretty much fits the big picture of greater genetic distance between
> tribes of Africans due to their longer time in isolation and
> Neanderthal blood mixed with some present-day Caucasians who come
> from Europe, etc. As to Adam, he either arrived with a small group
> of settlers near to or at Eridu in southern Mesopotamia roughly
> 7,000 years ago, or God fashioned him out of mud and placed him in a
> Garden, depending on whether you would prefer your Adam with or sans
> a navel.
>
> Dick Fischer, author, lecturer
> Historical Genesis from Adam to Abraham
> www.historicalgenesis.com
>
>
> -----Original Message-----
> From: asa-owner@lists.calvin.edu [mailto:asa-owner@lists.calvin.edu]
> On Behalf Of Rich Blinne
> Sent: Sunday, May 04, 2008 8:54 PM
> To: Gregory Arago
> Cc: Terry M. Gray; AmericanScientificAffiliation
> Subject: Re: [asa] Humanity and the Fall: Questions and a Survey
>
>
> On May 2, 2008, at 5:02 PM, Gregory Arago wrote:
>
>
> "The current view is not a founder pair but a founder small
> population in the 10K range." - TG
> Is this consistent with the idea of 'polygenism,' even if it doesn't
> address the 'multiregional hypothesis'? Does it not contradict the
> idea of 'monogenism'?
>
> Can you forgive my SoS question: whose view is the 'current view'
> and the 'present notion'? Is this what 'normal science' says? (And
> for a non-NS) Which fields does the 'current view' mainly draw upon?
>
> It seems to me that David C.'s post carefully left open more than
> one option, which I quite appreciate, not being a 'scientist' in a
> field that speaks about bottlenecks (though 'probka' means
> 'bottleneck/traffic jam' in Russian) or near extinction events. The
> consequences of a 'founder small population' instead of a 'founder
> pair' in sociology is significant, though not commonly discussed in
> the literature.
>
>
> All of this goes back to a very simple observation. The genetic
> diversity of people of African descent have greater genetic
> diversity than those who aren't. It gets a lot more complicated than
> this but there are basically two ways you can get this, bottlenecks
> and founder effects. When a population suddenly gets smaller in a
> bottleneck its genetic diversity also goes down. Likewise, when
> there is colonization the same happens. Out-of-Africa holds to a
> multiple founder effects and Multi-Regional-Evolution to
> bottlenecks. Another difference between the two approaches is MRE
> claims there is admixture of "modern" humans with Neanderthal, the
> evidence being some commonalities in the microcephalin gene in MtDNA
> found in fossilized Neanderthal. OOA says there is little or no
> admixture but that the Eurasia population were replaced by African
> ones. Both approaches give you dates and population sizes. NONE of
> the options or suboptions give you monogenism. That's why I prefer
> Adam and Eve in the ANE because both it and its alternative have the
> same theological problems. Note: the theological problems caused by
> evolution are still there even when you restrict yourself to
> genetics and so-called microevolution. David C's point was there are
> problems with uncalibrated molecular clocks giving accurate dates.
> Both sides agree with the size of the original population Terry
> quoted. More on this later.
>
> What we have here is a classic stage two science with two
> conflicting theories fighting for dominance. We are, however, on the
> cusp of stage three here and that is a very interesting story. Note
> what does not happen where both sides don't talk to each other, just
> publish in the popular literature and produce no falsifiable
> hypotheses like ID. Given the time frame is roughly the same as ID,
> this will give us a good comparison/contrast between the scientific
> approach and the ID approach. David C. mentioned the issue with
> molecular clocks and this reflects the battle between the
> paleontologists and the molecular biologists on how things are
> dated. This is also moving from stage two to stage three. The answer
> is to do both mirroring the massive success of the neo-darwinian
> synthesis. This has of late produced some very fruitful results. For
> example, we are getting the same answer out of both fields of the
> what and when concerning the speciation of mammals. We are even
> getting confirming evidence from ancient biological materials.
> Collagen from T Rex confirmed what the paleontologists have been
> telling us that dinosaurs are birds. The other thing that makes it
> much easier is since the human genome was produced five years ago
> the technology has taken off like a rocket -- and ID still produces
> no research. I would submit the fundamental difference between
> science now and fifty years ago is not a difference in the
> philosophy of science but rather the technology of science.
>
> Paul Harvey voice: "And now for the resssst of the story. Page two."
> In 2004, Osbjorn M. Pearson wrote "Has the Combination of Genetic
> and Fossil Evidence Solved the Riddle of Modern Human
> Origins?" [Evolutionary Anthropology 13:145-159 (2004)]. This was
> when the debate between OOA and MRE was in the second stage, trench
> warfare stage. By combining the genetic and archeological data the
> balance was tipping to the OOA side. Pearson said:
>
>
>> Debate over the origin of modern humans continues without a clear
>> end in sight. Currently, the genetic and fossil evidence is still
>> used to support two different interpretations of the origin of
>> modern humans. Some researchers claim that the genetic evidence is
>> compatible with either an Out-of-Africa or a Multiregional model,
>> while other scientists argue that the evidence supports only a
>> Multiregional model of evolution. I argue that the fossil record
>> and archeological evidence constrain interpretation of the genetic
>> evidence and imply that very little, if any, admixture with
>> Eurasian archaic hominins such as the Neanderthals occurred during
>> the spread of modern humans out of Africa.
>
> ...
>
>> First, the effective population size of [approximately] 10,000
>> individuals for our species would have to have arisen from a
>> bottleneck or series of bottlenecks long before the origin of
>> modern humans ... [RDB Note: this is what Terry quoted. This will
>> come back again so keep your eye on the ball.]
>
> ...
>
>> Future discoveries in genetic patterns or the genetic basis of
>> “modern” traits should help to narrow down even further the
>> possibilities with respect to exactly what happened with the origin
>> of modern humans. There is reason for optimism that these
>> discoveries will be made soon. [RDB Note: He was right.]
>
> Fast forward to 2008.
>
> Weaver and Roseman, New Developments in the Genetic Evidence for
> Modern Human Origins, Evolutionary Anthropology 17:69–80 (2008)
>
>> The genetic evidence for modern human origins was reviewed recently
>> in Evolutionary Anthropology by Pearson, so our goal is to
>> highlight new developments rather than attempt a comprehensive
>> review. For years, polarized Multiregional and Out-of-Africa models
>> for modern human origins were debated vigorously, but today there
>> is substantial agreement among specialists. One area of broad
>> consensus is that Africa or, more accurately, sub-Saharan Africa,
>> played a predominant role in the origins of modern humans. This
>> view is found even among researchers who argue against complete
>> replacement of nonmodern Eurasians. The importance of Africa is
>> clear not only from genetics, but also from the fossil record. On
>> the other hand, most researchers also agree that, at least in
>> principle, modern humans and nonmodern Eurasians, such as
>> Neandertals, could have interbred with each other. The fossil
>> record suggests that Neandertals and modern humans constituted
>> independent evolutionary lineages, but their recent common ancestry
>> leaves open the possibility of admixture. The open question is
>> whether there is any evidence of admixture.
>>
>
> What brought about the consensus? A better technique using short
> tandem repeat analysis (STR) rather than single nucleotide
> polymorphisms (SNP) was done. This produces much less ascertainment
> bias and thus allows us to do within-population variation on the
> global STR dataset. If you look at just the difference in genetic
> diversity between African and other locations this can be explained
> via multiregionalism with isolation by distance which is an
> equilibrium model. But, looking at in-population gives us greater
> precision. When looking at this there is a straight line
> relationship for every population with the diversity with distance
> from East Africa. In other words, we have a smoking gun for OOA. The
> farther you are from Africa the later the founder arrives and the
> further you are away from equilibrium. Isolation by distance has no
> such preference to the direction of the distance.
>
> Late last year a Bayesian analysis was done on 50 independent
> autosomal noncoding loci with six different models (African
> Replacement, Assimilation, Multiregional with instantaneous
> (bottleneck) and exponential growth). [Fagundes et al, Statistical
> evaluation of alternative models of human evolution, PNAS 104:45,
> 17614-17619 (2007)] The winning model based on posterior
> probabilities was the African Replacement Model with Exponential
> Growth (AFREG). After the model was determined, 5,000,000 different
> simulations under an approximate Bayesian computation (ABC)
> framework were done to get the parameters. Did you keep your eye on
> the ball and remember Terry's population size number? Note what came
> out as the ancient African population (12722). Also note that census
> populations (what we normally think of populations) can and often
> are quite larger than the effective number of diploid individuals.
>
> Table 1. Demographic and historical parameters estimated under the
> favored AFREG model
> Parameters†
> Median‡ 95% HPD§
> Speciation time for modern human, yr (TMH) 141,455 103,535–185,642
> Exit out of Africa, yr (TAS) 51,102
> 40,135–70,937
> Colonization of the Americas, yr (TAM) 10,280 7,647–15,945
> Size of archaic African population (NA-AF) 12,772 6,604–20,211
> Bottleneck size during speciation (NbMH) 600 76–1,620
> Bottleneck size when leaving Africa (NbAS) 462 64–1,224
> Bottleneck size when leaving Asia (NbAM) 452 71–1,280
>
>
> † Population sizes are given in effective number of diploid
> individuals.
> ‡ Median value of the marginal posterior density.
> § The 95% highest posterior density interval.
>
> What about the admixture of humans and Neanderthal? Currently there
> isn't enough information to prove or exclude it. We are still in
> stage 2 there. Given the speed at which the genetic technology is
> moving I would not be surprised to be at stage 3 soon. This is a
> rather easy prediction to make. (Just don't force me to pick which
> one is right. :-)
>
> Rich Blinne
> Member ASA
>
> P.S. I am including the glossary from the 2008 Evolutionary
> Anthropology article to explain the terms used in this post:
>
> Admixture—transfer of genes between two populations that had
> previously been isolated from each other.
>
> Ancient DNA—a DNA sequence retrieved from a biological sample of a
> dead organism, often coming from an extinct taxon.
>
> Ascertainment bias—genetic loci are usually discovered by finding
> differences among individuals in a small sample, then typed for a
> larger sample. This nonrandom discovery process often biases
> estimates of population genetic parameters such as measures of
> within-population genetic diversity, among-population
> differentiation, linkage disequilibrium, and tests for departures
> from mutation-drift-equilibrium. The only way to eliminate
> ascertainment bias is to completely resequence all the individuals
> in the study; that is, the discovery sample is the same as the study
> sample.
>
> Autosomal locus—a position on one of the paired (non-sex)
> chromosomes.
>
> Bottleneck—a sharp contraction followed by a recovery in population
> size.
>
> Census population size—the actual number of individuals in a
> population.
>
> Coalescence time—the time in the past when all DNA sequences in a
> sample shared a last common ancestor (time to the most recent common
> ancestor).
>
> Directional natural selection— when natural selection favors a
> phenotype that differs from the population mean, resulting in a shift
> of the mean.
>
> Effective population size—a population genetics parameter that
> equals the number of breeding individuals in an idealized population
> that would have as much genetic drift as is in the actual population.
>
> Founder effect—when a small subset of a population moves to a new
> geographic region, its genetic diversity is lower than and is often
> unrepresentative of the original population. A founder effect
> produces a genetic signature similar to a bottleneck.
>
> Gene flow—transfer of genes between populations by migration of
> individuals between the populations and subsequent mating.
>
> Gene tree—a tree that shows the evolutionary relationships among a
> sample of DNA sequences.
>
> Genetic distance—a statistic that reflects some aspect of genetic
> variation between two populations, sometimes standardized by the
> variation found within them.
>
> Genetic drift—chance genetic changes in a population due to finite
> size.
>
> Genetic locus—a particular position in the genome.
>
> Haplotype—the presence of particular nucleotides over a stretch of
> DNA that tend to be inherited together.
>
> Isolation by distance—an equilibrium model that predicts a positive
> relationship between genetic and geographic distance. This
> relationship occurs because individuals tend to migrate short
> distances to find mates and because long-range migrations are rare.
>
> Linkage disequilibrium—deviation from a random association of the
> nucleotides present at a set of genetic loci.
>
> Microsatellite—a rapidly evolving block of DNA in which a simple
> DNA sequence is repeated multiple
> times and individuals vary in their number of repeats.
>
> Mitochondrial DNA—a short DNA molecule that is found outside of the
> cell nucleus. It traces maternal lines of descent because it is
> inherited only from the mother.
>
> Mutation-drift-equilibrium—a population is said to be at mutation-
> drift-equilibrium when a balance (equilibrium) has been reached
> between the genetic variation introduced by mutation and that lost
> by genetic drift.
>
> Negative natural selection— when natural selection acts to remove
> low-frequency novel genotypes from a population.
>
> Nuclear DNA—the bulk of an individual’s DNA, which is found
> within the cell nucleus.
>
> Population subdivision or structure—a population is said to be
> subdivided or structured when it is divided into a set of local groups
> and there is nonrandom mating across groups.
>
> Population tree—a tree that shows the evolutionary relationships
> among a set of populations.
>
> Positive natural selection— when natural selection acts to shift
> low-frequency novel genotypes to high frequency or fixation within a
> population.
>
> Purifying natural selection— another term for negative natural
> selection.
>
> Range expansion—an increase in the geographic range occupied by a
> population or species. Range expansions are often linked with
> increases in population size.
>
> Short tandem repeat (STR)— another term for a microsatellite.
>
> Single nucleotide polymorphism (SNP)—a position in the genome where
> individuals differ with regard to which nucleotide is pre-
> sent.
>
> Stabilizing natural selection— when natural selection favors the
> mean phenotype, preventing a shift of the mean.
>
> Y-chromosome—a sex chromosome that is paired with the X chromosome
> in males, whereas females have two X chromosomes. The
> nonrecombining portion traces paternal lines of descent.
>

________________
Terry M. Gray, Ph.D.
Computer Support Scientist
Chemistry Department
Colorado State University
Fort Collins, CO 80523
(o) 970-491-7003 (f) 970-491-1801

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Received on Mon May 5 02:14:50 2008