I don't know if this was posted while I was away, but it seems that
the "Y-chromosome Adam" date and time has coincided with that
of "Mitochondrial Eve", ie. 100-200 kya in Africa. Here is an
extract from the SCIENCE article:
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Y Chromosome Shows That Adam Was an African
In the beginning there was mitochondrial Eve-a woman who lived in
Africa between 100,000 and 200,000 years ago-and was ancestral to
all living humans. Geneticists traced her identity by analyzing DNA
passed exclusively from mother to daughter in the mitochondria,
energy-producing organelles in the cell. To test this view of human
origins, scientists have been searching ever since for Eve's genetic
consort: "Adam," the man whose Y chromosome (the male sex
chromosome) was passed on to every living man and boy.
Now, after almost a decade of study, two international teams have
found the genetic trail leading to Adam, and it points to the same time
and place where mitochondrial Eve lived. Described this month at a
symposium on human evolution at Cold Spring Harbor Laboratory in
New York, the genetic trail is so clear that it allows researchers to
compare the migration patterns of men and women tens of thousands
of years ago (see sidebar). It even pinpoints the living men whose Y
chromosomes most resemble Adam's: a few Ethiopians, Sudanese,
and Khoisan people living in southern Africa, including groups once
known as Hottentots and Bushmen.
[...]
The Stanford researchers got the system working full-time this year.
So far, they have found 93 new polymorphisms in the Y
chromosomes of men from around the world. "It's a major
breakthrough-unquestionably," exults geneticist Luca Cavalli-Sforza,
head of the lab where Underhill has done this research. And when the
team started sorting these polymorphisms into a phylogenetic tree,
they found one particularly ancient marker, called M42. In its most
ancient form, shared by other primates, this marker is an A, or
adenine. Today, it is found only in Africa, in just a few of the 900
males they scanned- 15% of the Khoisan, and 5% to 10% of the
Ethiopians and Sudanese. These men must have inherited this ancient
form from a common ancestor. "We think we have tagged Adam,"
says Underhill, who reported the work at this week's annual meeting
of the American Society of Human Genetics in Baltimore.
The data further show that sometime in the past 100,000 to 200,000
years, this M42 site underwent a mutation-a change from A to T
(thymine) in one of Adam's descendants. While men with the A
stayed in Africa, some of the Africans with the T left the continent
and spread around the globe. Today, "all men outside of Africa, as
well as most African men carry the T." says Underhill.
Meanwhile, another team headed by geneticist Michael Hammer at
the University of Arizona, Tucson, surveyed another noncoding
region of the Y chromosome in 1544 men worldwide and found the
same pattern. the DNA sequences varied among individuals, but
Hammer found that the variants cluster into 10 major groups, known
as haplotypes, which occur in different frequencies in different
populations.
Haplotype 1A, defined by an A at a particular site, appears to be
ancestral because the A is found in chimpanzees, and Hammer's team
found that in humans, it occurs only in some Africans. "It's at the
highest frequency in the Khoisan," he says- the same population
fingered by Underhill's team. Although the ancient form of 1A
persisted in some groups in Africa, it also underwent a change to a G
(guanine) 150,000 to 200,000 years ago in one descendant of
Adam's. Like the T in Underhill's site, this form was carried out of
Africa when men moved away and replaced other males around the
globe.
Both sets of results bolster the so-called Out of Africa model of
human origins. "We think that anything existing in Asian males was
replaced by this," says Hammer. Underhill agrees: "I think this
speaks persuasively for an Out of Africa origin for modem humans."
But Hammer's group, whose findings are in press in the journal
Molecular Biology and Evolution, has added a twist to the scenario.
These researchers also see evidence that some of Adam's descendants
who emigrated to Asia later returned to Africa, with a new mutation
on the Y that arose in Asia. In addition, Hammer says that African
males could have interbred with Asian females, and if traces of those
women's genes may still be in our nuclear genome- Indeed, other
researchers have already reported signs of an ancient Asian origin for
a 5-globin gene (Science, 25 April, p. 535).
So, Hammer favors a model that shows a wave of modern people
coming out of Africa, replacing most of the genes of ancient people,
but interbreeding enough to add some ancient non-African genes to
our genome. Paleoanthropologist Fred Smith of Northern Illinois
University in De Kalb, who proposed one such intermediate model,
predicts that like so much of human history, Ode real story "won't be
black or white. Genes and fossils are showing that population
dynamics are a lot more complex than we thought."
(Gibbons A., "Y Chromosome Shows That Adam Was an African",
Science, Vol. 278, 31 October 1997, p805)
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I find this very exciting because of its obviously similarity to the
Biblical story. Previously I have maintained a pre-Adamite view,
which would place Adam about 40,000 years ago, when there was a
cultural explosion:
"Steven Mithen, a lecturer in archaeology at the University of
Reading...believes modern humans emerged after a final redesign of
the brain, resulting in a "big bang" of cultural advances that
started 40,000 years ago in Europe with the production of objects
such as beads, pendants, statuettes, paintings and engravings. Rock
art appears to have been most prolific in Europe, after this cultural
big bang, but Mithen and others point out that some wall engravings
in Australia may date back around 40,000 years..." (Patel T.,
"Stone Age Picassos", New Scientist, 13 July 1996, p34)
This still fits with an upper limit of the Biblical genealogies if
they were stretched. However, while I don't believe the
genealogies are father-son, I have doubts that they can be
stretched too far as the YECs point out:
"To stretch the genealogy of Genesis 11 to cover a period of over
100,000 years is to do violence to the chronological framework of all
subsequent Bible history and prophecy. Approximately 2,000 years
covers the history of the Church up to the present. Before Christ's
first coming, the history of Israel covered a period of 2,000 years;
and after Christ's second coming, according to Revelation 20, there
will be another 1,000 years of earth-history before the commencement
of the eternal state...The incongruity of insisting upon 100,000
years between Noah and Abraham, while granting that the entire
history of redemption from Abraham to the eternal state may be only
four or five thousand years, becomes obvious. To be sure, it was by
means of Biblical analogies that we were able to find possible gaps
in the genealogy of Genesis 11. But the point we now wish to
emphasize is that those very analogies serve also to limit our
time-scale for Genesis 11. The gap between Amram and Moses was 300
years, not 30,000. And the gap between Joram and Uzziah in Matthew
1:8 was 50 years, not 5,000. On the basis of the analogy of Biblical
chronology, therefore, we maintain that it is very hazardous to
assume a period of 100,000 years between the Flood and Abraham."
(Whitcomb J.C., & Morris H.M., "The Genesis Flood", 1964 reprint,
pp485-486)
OTOH, a too early date for Adam, which leaves him not the actual
physical ancestor of all modern men, has major theological problems.
The latest evidence above is converging on a date of between 100-200
kyrs in Africa for all living Homo sapiens' last common ancestor. I
am a bit skeptical about the ability of molecular clocks to keep
accurate time. But I am prepared to consider the possibility that
the origin of man took place in Africa between 100-50 kya and the
Biblical story of man's origin, temptation and fall (not to
mention the Flood) may be theologically accurate legends, written
and preserved with supernatural assistance by Abraham's ancestors
(and in garbled form by other peoples), that summarises these complex
historical facts, albeit presented in a Middle East setting.
It is perhaps noteworthy that one of the rivers in the Garden of
Eden "compasseth the whole land of Ethiopia" (Gn 2:13), where the
Mitochondrial Eve and Y-Chromosome Adam are thought to have come
from.
God bless.
Steve
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Stephen E (Steve) Jones ,--_|\ sejones@ibm.net
3 Hawker Avenue / Oz \ Steve.Jones@health.wa.gov.au
Warwick 6024 ->*_,--\_/ Phone +61 8 9448 7439
Perth, West Australia v "Test everything." (1Thess 5:21)
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