Joel Duff asks if we have discussed the Science article cited below.
Beginning late in November, 1995, I asked in the thread, "A Question for
TE's," if Jesus' Y-chromosome indicated he was descended from that male of
270,000 years ago. If his Y-chromosome did so indicate, then, since he did
not have a human father, we must conclude that he was made to look like he
had a human father. If his Y-chromosome indicated otherwise, then we have
in principle (even thought the technology was not available then) a
physical test for his uniqueness.
It would seem that the second alternative is not possible, and so we are
left with the idea that God made a man who looked like he had such-and-such
an ancestor, whereas he actually did not. Then, just because Adam may have
genetically looked like an animal, are we to conclude that he necessarily
did descend from an animal?
This argument caused a bit of stir. But I am not willing to conclude that
anyone was convinced by my reasoning!
Russell Maatman
----------
> From: R. Joel Duff <Duff@siu.edu>
> To: Evolution@calvin.edu
> Subject: Y-chromosome and age of "men"
> Date: Monday, September 16, 1996 5:59 PM
>
> Glenn, group,
>
> Just ran accross this brief summary article at:
>
> www.gene.com/ac/WN/index.html
>
> The article is a summary of a Science article from 1995. A little dated
> and I don't know if anyone discussed it last year but it seems somewhat
> relative to recent discussion and Glenn I am particulary interested with
> what you do with this type of information (not that I can see that it
> doesnt' fit into your model).
>
> --------
> MEN HAVEN'T CHANGED IN 270,000 YEARS
>
> By Sean Henahan, Access Excellence
>
> -------------------------------------------------------------
>
> NEW HAVEN, CT- A survey of genetic information contained in
> the Y chromosomes of modern day men suggests that Homo
> sapiens descended from a single group of male ancestors, and
> that this occurred more recently than previously believed.
>
> Researchers at Yale University evaluated samples of DNA from
> 38 men from all over the world. Surprisingly. no sequence
> variations were found in a 729-base pair intron near a gene
> thought to be involved in sperm or testes development. In
> contrast, the corresponding sequence in gorillas,
> chimpanzees, and orangutans did show significant
> polymorphisms.
>
> Based on the assumption that this lack of sequence variation
> is attributable to ancestry and not other causes, the
> researchers estimate the divergence occurred about 270,000
> years ago. Previous estimates have put mankind's origins much
> further back in time.
>
> This discovery adds to growing evidence that modern humans
> share the same basic genetic makeup, and that population
> differences represent relatively minor variations in the
> overall spectrum of human diversity, said Robert L. Dorit, an
> assistant professor of biology at Yale University. Dr. Dorit
> collaborated with researchers from the University of Chicago
> and Harvard University on the project.
>
> "If we all descended from a recent common ancestor, and if
> the history of human populations is a history of movement and
> gene flow, then the differences between us, as socially
> striking as we may wish to make them, are largely irrelevant
> from a biologist's standpoint," Dorit said.
>
> The new findings appear to corroborate the timeline of the
> controversial "African Eve" hypothesis, first proposed in
> 1987. That hypothesis holds that all humans are descended
> from female ancestors who lived in Africa about 200,000
> years. Those studies focused on purported regular, clock-like
> mutations of genes located in the mitochondria,
> energy-producing structures outside the cell nucleus that are
> present in the egg and thus inherited only from mothers.
>
> The Yale study focused on the even slower clock-like
> mutations in the Y chromosome, the male sex chromosome passed
> from father to son. The researchers selected the Y chromosome
> because it contains the only genetic material besides
> mitochondrial DNA that is inherited from just one parent. The
> genetic material on all other chromosomes is inherited from
> both parents and is recombined, thus making it more difficult
> to reconstruct an evolutionary history.
>
> The new research also appears to rules out an opposing theory
> that modern humans simultaneously evolved in different
> regions of the Old World from an earlier human ancestor -
> Homo erectus - who migrated out of Africa perhaps 1 million
> years ago. The lack of genetic variation found in the Yale
> study makes it highly unlikely that independent Y chromosome
> lineages have been evolving for a million or more years along
> separate paths, Professor Dorit said.
>
> "The lack of genetic variation in the Y chromosome region we
> examined also makes it impossible for us to reconstruct the
> geographic location of the last common ancestor," Dorit
> noted. "The African Eve hypothesis, on the other hand, is
> based on a mutation rate in mitochondria that is at least 10
> times faster than the mutation rate in the Y chromosome.
> Therefore, the greater number of mutations found in the
> mitochondria of native Africans indicates a longer history
> and a probable African origin for modern humans. We hope to
> be able to confirm an African origin by looking at another
> segment of the Y chromosome that is mutating slightly faster
> than our original segment, which could reveal subtle regional
> genetic differences," he said.
>
> Dr. Dorit and colleagues compared the same sequence of 800
> base pairs of nucleotides in humans to that of chimpanzees,
> gorillas and orangutans so as to establish the mutation rate
> in the Y chromosome. Humans are believed to have shared a
> common ancestor with chimpanzees and gorillas about 5 million
> years ago, and with orangutans about 14 million years ago.
>
> "The idea was to get a snapshot of this part of the Y
> chromosome in a worldwide sample of humans that would help us
> establish some kind of evolutionary tree connecting human
> populations. We were very surprised to find no genetic
> differences in humans, although we found mutations as
> expected when we studied the primates. This probably means we
> are a very young species," noted Dorit.
>
> It is still possible to hypothesize that Homo sapiens is
> actually much older than 270,000 years, emphasized Dr. Dorit.
> For example, it is possible the "genetic slate" was wiped
> clean recently by a beneficial mutation that caused a rapid
> sweep of that individual's genes throughout the population by
> natural selection. Another possibility is a significant
> reduction in the population of Homo sapiens, which population
> geneticists call a "bottleneck,". Such an event would
> significantly reduce genetic diversity, he said.
>
> "However, evidence now is coming in from other parts of the
> human genome besides the mitochondria pointing to a recent
> origin for modern humans. In addition, molecular clocks
> appear to be ticking at various speeds in different genes
> that together can help us measure human evolution with
> greater accuracy. We must remember, however, that we are
> reconstructing the history of molecules here. While that
> history is not independent of the history of the organisms in
> which they are found, molecules have agendas of their own,"
> Dorit said.
>
> For more information on this study please refer to: Science,
> 5/26/95, Dorit et al.
>
>
> Joel Duff
>
>