Re: What DNA change allows for current Mayan Indian head structure

Sorry about the wait, I thought I'd answered this. The answer is that the
gene for head shape in the Yucatan Maya were those for their particular
elongated head. The people liked that head shape and then developed the
custom to bind their kid's heads so they'd have that shape when they grew
up. So the binding has no effect on Mayan head shape genes, but represents
a preference for this head shape. That suggests it would be subject to
sexual selection and thus increase in the populations. 


The issue is that undefined genes (not a single gene) are likely involved
in determining head shape. These genes that cause an elongated head shape
were likely already present at some level in the population of proto-Maya
people and gave the holders of these genes elongated heads. The people with
the elongated head shape were likely to be thought attractive and
desirable. Hence, they had more children and the genes for the head trait
got more common over time. Eventually, the frequency of this head shape
became so common that anyone with a non-elongated head would be freakish.
At this point, I would bet that people wanted to ensure their children had
this head trait, and so then began to bind their kid's heads to ensure it.
This binding had no effect on the head shape genes, but at this point, the
elongated head shape had become common or dominant in the population to the
point everyone expected that elongated skull. That people bound their kids
heads was simply to ensure they had that desirable head shape, and had no
effect on the actual gene distribution.

Now, I was down in Yucatan just 4 weeks ago and I didn't see any people
with heads shaped like this, so your statement that head binding was
associated with a modern population of  genetically elongated head shapes
is a bit of a mystery to me. I had taken at face value that there exists
today somewhere in Yucatan Maya with a genetically elongated head, but I
saw no evidence for it where I was.