[ExI] People are the same?

[BillK]

2011/7/29 Dan wrote:
> It depends on what the background rate of change is and what kind of impact
> these changes have. E.g., imagine a SNP change that has zero impact because
> it's for a structural protein for something that's rarely produced and it
> codes for part of the structure that is tolerate of having many different
> sequences of amino acids. In that case, wild changes in it wouldn't have
> much impact on the phenotype and it's likely drift would be the norm... (Or
> this is my lay understanding.:)
>
>

I think Eugen was exaggerating a bit when he said that humans were the
same as 50,000 years ago.
Both groups have two arms, two legs and one brain and outwardly look
similar, but there have been many changes in the genome. It is the
effect of a huge increase in the human population since 50,000 years
ago. The larger the population, the more mutations occur and encounter
selection pressures.

<http://www.news.wisc.edu/14548>

Quote:
the researchers found evidence of recent selection on approximately
1,800 genes, or 7 percent of all human genes.

The biggest new pathway for selection relates to disease resistance,
Hawks says. As people starting living in much larger groups and
settling in one place roughly 10,000 years ago, epidemic diseases such
as malaria, smallpox and cholera began to dramatically shift mortality
patterns in people. Malaria is one of the clearest examples, Hawks
says, given that there are now more than two dozen identified genetic
adaptations that relate to malaria resistance, including an entirely
new blood type known as the Duffy blood type.

Population growth is making all of this change occur much faster,
Hawks says, giving a nod to Charles Darwin. When Darwin wrote in
"Origin of the Species" about challenges in animal breeding, he always
emphasized that herd size "is of the highest importance for success"
because large populations have more genetic variation, Hawks says.

The parallel to humans is obvious: The human population has grown from
a few million people 10,000 years ago to about 200 million people at
A.D. 0, to 600 million people in the year 1700, to more than 6.5
billion today. Prior to these times, the population was so small for
so long that positive selection occurred at a glacial pace, Hawks
says.
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BillK