[Marxism] Tweaking of DNA dating on human evolution
markalause at gmail.com
Sun Sep 6 21:51:40 MDT 2009
Again, I claim to be nothing but a rank amateur in following these
things. And I'm not entirely sure what the point of confusion is
Let's start by throwing out the entire Biblical language the media
used to spin the original story. The term "Eve" was in the post
because it was in the story. It was in the story because it's the
sort of hype that gets the cover of magazines.
The mitochondrial DNA is NOT the result of the DNA involved in the
genetic mingling of the sperm and the egg...the X and Y chromosomes in
the nucleus. Mitochondrial DNA is OUTSIDE the nucleus and helps to
fuel the cell. What you have of it is what the original egg had. So
it only comes from yo mamma.
Think of it this way: my mother had only boys. We have her
mitochondrial DNA. We do not contribute eggs to the next generation,
so that line comes to an end.
So, there WERE many female contemporaries "Eve." They had kids. We
are also their descendants. We just don't have their mitochondrial
DNA, because--at some point--those lines came to an end.
But here's where it gets interesting and perhaps is the source of the
confusion here. We've been talking about the mitochondrial DNA from
the same woman back at a certain point in time...AND we are talking
about tracing different mitochondrial DNA after her.
DNA of any sort doesn't reproduce itself exactly. It changes over
time, and at a roughly predictable rates. Most mutations don't really
affect anything and they never affect anything if they're in the
mitochondrial DNA anyway...it just isn't used to pass on information
for reproduction. So, if you can use those mutations to trace
relationships among human populations and make some fascinating
extrapolations about human migration in prehistory, etc.
For example, they make a distinction between the population that left
Africa on that last pulse and those that remained. The group that
remains will have the widest variety of these mutations, while the one
that migrates to another place will have a smaller variety of them.
So they all start with mitochondrial DNA but then branch out into
greater varieties of them. All the branches are identifiably of the
original, but represent subsets with new mutations as well.
These things DO have remarkable implications for evolution and human
prehistory, though not those that Shane fears. We are now able to say
incredible things with a remarkable level of certainty about what
groups of people were doing in prehistory.
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