Re: Chimp, Y, and social structure


Paul Crowley wrote:

>
> Any you STILL duck my main point: Even
> IF we were sure of the mating system (which
> we certainly are not) how could it have any
> significant effect on the gene structure?

I chose to ignore the business about hemophilia because, although it is
a sex linked trait, the gene is on the X chomosome, therefore moot
regarding this discussion.

The surprising thing about the chimp Y chromosome is that it has fewer
genes than the human Y. The human Y has a conservative feature where
the gene folds back on itself and thereby provides a self correcting
copy of itself which preserves. By the principle of parsimony in
evolution, if our species relied on sperm competition for male gene
expression, all genes on the Y unrelated to sperm production would get
lost as they are on the chimp Y.

Thus the implication is that humans had a different social arrangement
than chimps. The present human population has pair bonding, more or
less. (Data from early Mormon polygamists show that the maximum
reproductive potential was realized with between 2 and 3 wives, for
what that is worth.) Orangs have pair bonding and when that genome is
sequenced, it should be illustrative.

Harem holding, as practiced by gorillas, doesn't rely on sperm
competition but they are the most dimorphic of the primate species.

Thus we have a conundrum. We currently have pair bonding, a situation
only found in the most solitary primate species. We have genetic data
that suggests a harem situation, or early pair bonding. (I will confess
that my knowledge of genetics doesn't allow me to understand how they
can time genetic changes, but they so assert.) Then we have that timing
of pair bonding and the fossil record of the lessening of sexual
dimorphism in the fossil record not correlating.

We can only hope that more data clears the picture instead of muddying
it.

BTW, Don Johansen's find of the "First family" soon after the discovery
of A. afarensis is the most complete survey of an early hominid group
in existence.

.

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