Is there scientific evidence for near-human extinction in the past?

Date:   8/17/2005 7:23:21 AM ( 19 y ago)

First an article from http://www.cartage.org.lb/en/themes/Sciences/LifeScience/PhysicalAnthropology/HumanGeneticEvolution/OriginsofthePresent/OriginsofthePresent.htm

A. Homo sapiens sapiens is thought to have evolved in Africa some 200,000 years ago. By 100,000 years ago, the populations were already diversified in Africa. A small group crossed into the Middle East at Suez and spread throughout Asia and Europe, reaching Australia some 40,000 years ago and America some 20,000 years ago (highly disputed date).

B. Mitochondrial DNA is particularly interesting, since it is maternally inherited and therefore does not recombine during meiosis. There are many versions of mtDNA today, all of which descended from a single female who lived some 200,000 years ago. There were many other female ancestors, but their mtDNA eventually was lost. Many think that female lived in Africa (though some argue for Asia).

C. The Y chromosome also does not recombine except for the pseudoautosomal region. Diversity in the Y chromosome is generated only by mutations, which accumulate over time. It is theoretically possible to identify a "founding" Y chromosome, just as in the case of mitochondria. The date given for such a founding father is of the same order of magnitude as mitochondria, some 200,000 years ago. Both dates are subject to large error because of the ASSUMPTIONS of rate of accumulation of MUTATIONS. (emphasis mine)

By comparing DNA from different humans around the world, it has been found that all humans share roughly 99.9% of their genetic material—they are almost completely identical, genetically.7  This means that there is very little polymorphism, or variation.  Much evidence of this genetic continuity has been found.  For example, Dorit et al.8 examined a 729-base pair intron (the DNA in the genome that is not read to make proteins) from a worldwide sample of 38 human males and reported no sequence variation.  This sort of invariance

‘ …  likely results from either a recent selective sweep, a recent origin for modern Homo sapiens, recurrent male population bottlenecks, or historically small effective male population sizes … any value of Q [lowest actual human sequence diversity] > 0.0011 predicts polymorphism in our sample [and yet none was found] … .  The critical value for this study thus falls below most, but not all, available estimates, thus suggesting that the lack of polymorphism at ZFY [a locus, or location] is not due to chance.’

After citing additional evidence of low variation on the Y chromosome, they note in their last paragraph that their results ‘are not compatible with most multiregional models for the origin of modern humans.’ Knight et al.9 have had similar research results:

‘We obtained over 55 kilobases of sequence from three autosomal loci encompassing Alu repeats for representatives of diverse human populations as well as orthologous sequences for other hominoid species at one of these loci.  Nucleotide diversity was exceedingly low.  Most individuals and populations were identical.  Only a single nucleotide difference distinguished presumed ancestral alleles from descendants.  These results differ from those expected if alleles from divergent archaic populations were maintained through multiregional continuity.  The observed virtual lack of sequence polymorphism is the signature of a recent single origin for modern humans, with general replacement of archaic populations.’

These results are quite consistent with a recent human origin and a global flood.  Evolutionary models of origins did not predict such low human genetic diversity.  Mutations should have produced much more diversity than 0.1% over millions of years.  And yet this is exactly what we would expect to find if all humans were closely related and experienced a relatively recent event in which only a few survived.  Research is needed to determine what variation should actually be present in the human genome—what would we expect within an evolutionary framework, and how does that compare with what we find?  These results could have a great impact on biological evolution, population genetics, and could provide telling results about the age of the humankind.  It could also affect the so-called molecular clock.

Another study concluded with the possibility that 50 individuals may have founded the entire population of Europe.  This evidence is also quite consistent with a historical global flood.  Research is needed on the implications of this data for the flood of Genesis.  Certainly, humankind has undergone a relatively recent (tens of thousands of years at most, within an evolutionary time frame) population bottleneck.  However, it must be further investigated as to the proportionality of evolutionary dates to the creation model, and as to how the molecular clock can be adequately explained in such a context.  Data aiding this understanding has already been published.5

We should also seek to understand genetic evidence in the context of the tower of Babel event.  Evidence exists that, after the bottleneck, ‘the [human] population rebounded in a series of separate, rapid expansions on different continents.’12  This too seems consistent with Biblical events in Genesis 11.  Surely, much research is needed to expand ideas about such genetic evidence to determine its consistency with the Bible and its inconsistency with, for example, the various evolutionary out-of-Africa models.  Different models of human history are hotly debated in the scientific community today.13

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