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Subject: Re: [DNA] Lactase persistance started about 7,500 years ago
Date: Sat, 29 Aug 2009 11:39:41 -0400
Can one really prove that a selective pressure caused a mutation to
prevail?
If drift was responsible for a mutation to increase, and then people
found that milk
was readily digestible, it could account for both an increase in
dairying and an increase
in a particular haploblock in a population without selection. If
natural selection was the
primary force, then what exactly caused the demise of this
"deleterious", yet
ancestral genotype in this case? I want the researchers to come up with
a plausible
explanation because I don't buy it either. Indigestion is not enough to
cause such
a drastic change IMHO.
I just don't see how lactose intolerance could have wiped out a
population. My sister
is supposed to be lactose intolerant according to this marker, yet she
is not. Many
other genetic genealogists drink milk just fine and are supposed to be
lactose intolerant.
Yes, the flora of the gut could have adapted, I suppose. But I want to
know why that
did not happen in ancient times. If there is a mathematical reason why
this is natural
selection and not drift, then can someone explain it to those of us who
are math
challenged?
Kathy J.
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