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Feedback 2011
Y-chromosome Adam and the Cambrian explosion
Published: 22 January 2011(GMT+10)
Image iStockphoto
This weekend’s feedbacks are answered by CMI-US’s geneticist
Dr Robert Carter. First, a question about “Y chromosome Adam”,
and second, about the Cambrian Explosion and modern seafloor
life:
Dear CMI,
I have question relating to human Y–DNA haplogroups. It is claimed that Y–DNA
haplogroups allegedly “disprove” the Creationist “Out-Of-Ararat”
model of human migrations and “prove” the Darwinist “Out-Of-Africa”
model. The claim is that “Y Chromosome Adam” gave rise to two major
sub-clades–A and BT. All living human Y-DNA haplogroups, except for A, are
supposedly descended from Y-DNA haplogroup BT by way of two other major sub-clades–B
and CT. The first carrier of Haplogroup CT (a.k.a. “Eurasian Adam”)
is said to have lived in Africa and his descendants supposedly later migrated out
of Africa to the Middle East becoming ancestral to all modern human male lines except
for A and B which are both found almost entirely in Africa. Because of this, many
Darwinists allege that this proves that humanity originated or “evolved”
in Africa and migrated to other parts of the world from there rather than migrating
from Babel in the Middle East following the flood to other parts of the world.
How do human Y-DNA haplogroups fit with the biblical model of human migrations and
with the Table of Nations in Genesis 10?
Thanks in advance.
God bless,
Dylan
Dr Carter responds:
Dear Dylan,
Great question.
1) All human males share a very similar Y chromosome. This means we have a recent
common ancestor. With the publication of the chimp Y chromosome last spring (only
~70% identical to human1),
evolutionary theorists are being forced to decide between two uncomfortable choices.
Either our common ancestor with chimps is much further removed than 6.5 million
years or Y–chromosome Adam is much younger than 90,000 years. The timing of
Y–chromosome Adam is not as friendly to evolutionary theory as was once assumed.
The fact that some Africans are very different from other people in the world (including
other Africans) indicates to me that they probably had different demographic history
than other world populations and this led to extreme genetic divergence.
2) To draw a tree of Y chromosomes that traces back to a single individual, the
assumption of a molecular clock is always (I have yet to see an exception) employed
by evolutionary theorists. They assume that mutation rates are constant among all
populations throughout our entire history. Corollary to this, they assume generation
times have remained constant and that sub-population sizes, growth rates, and other
demographic factors have been equivalent throughout time.
I wrote an
article that discusses the molecular clock hypothesis and its relation to
the Recent African Origins hypothesis at length for our Journal of Creation.
My arguments in the article above are mainly for Mitochondrial Eve, but they apply
just as well for Y-chromosome Adam. If the molecular clock is not valid, the root
cannot be placed anywhere on the tree with confidence. This is a critical point
and should answer your question.
The fact that some Africans (not all!) are very different from other people in the
world (including other Africans) indicates to me that, rather than being part of
the most ancient human population, they probably had different demographic history
than other world populations (a population broken up into many small tribal groups
is but one possible factor) and this led to extreme genetic divergence.
Sincerely,
Robert Carter
Next, a question about how seafloor life might relate to
the Cambrian explosion:
Dear CMI: I have just read an amazing article about a manned submersible that reached
the ocean floor (6 miles down!) back in the 1960s. What is even more amazing is
that they discovered life down there! There is no doubt that life that could survive
such an extreme environment must be wonderfully and fearfully made, and would have
a very special design. Could it be that the strange creatures found in the so-called
“Cambrian explosion” and the creatures that live at the bottom of the
ocean are one and the same? Does CMI have a view on this?
God bless.
Stephen & Ruth.
The deep ocean floors are full of weird and unexpected creatures. Species diversity
is incredibly high, with more new species per square area than most other environments
on earth, which is strange if you consider that environmental differences across
the ocean floors of the world are almost non-existent.
Dr Carter responds:
Dear Stephen and Ruth,
The deep ocean floors are full of weird and unexpected creatures. Species diversity
is incredibly high, with more new species per square area than most other environments
on earth, which is strange if you consider that environmental differences across
the ocean floors of the world are almost non-existent (dark, high pressure, no light,
extreme cold, and mud everywhere). The deep ocean has also been a source of speculation
throughout the centuries. There was one ill-fated but popular idea that the ocean
floor was covered in a proto-life ooze that was constantly giving rise to new life
forms (see Bathybius haeckelii
and a ‘reign of terror’).
Most of the creatures that live in the abyss, however, are versions of familiar
critters from shallower waters (starfish, worms, etc.). All of these phyla appeared
suddenly in the “Cambrian explosion”, but so did all of the extant phyla
on earth (for more information, see
The Greatest Hoax on Earth, ch. 7). Sadly, we cannot correlate
the ocean bottoms with the Cambrian explosion.
Thanks for the intriguing question and thank you for showing interest in our ministry.
Sincerely,
Robert Carter
Related articles
Further reading
Reference
- Hughes, J.F., et al., Chimpanzee and human Y chromosomes
are remarkably divergent in structure and gene content, Nature 463:536–539,
2010. Return to text.
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