human genetic diversity

William Tivol tivol at
Tue Aug 5 08:46:47 EST 1997

Guillermo Barron (gbarron at wrote:

: Now I don't know if in fact unrestrained incestuous reproduction would
: occur frequently enough to affect the human gene pool in any meaningful
: way.

	Likely not; however, it will likely produce a number of individuals
having lesser fitness.

:  But it does seem clear that heterogeneous mating (if I can call it

	Do you mean "non-incestuous" when you say "heterogeneous"?

: that) *is* widespread. Up until very recently most humans mated not only
: within their own race but within relatively narrow tribal and geographical
: limits. This has of course changed quite radically within
: the last century or so with the advent of global migration.   My question
: is: does mating between genetically different populations increase or
: decrease diversity?   In other words, would Laplanders mating with
: Yanomani, and Tibetans mating with Cherokees increase or decrease human
: genetic diversity?

	Yes, diversity would be increased.  Actually, it does not produce 
new alleles, per se, but it leads to the combination of different genes 
which may confer greater fitness.  That is, many genes working in combi-
nation may lead to a healthier individual under some environmental circum-
stances; whereas each gene alone may decrease fitness.  In this case, the
lack of mixing would lead to the loss of the genes, while interbreeding
would preserve them.

: I'm
: simply not sure what humans ought to do to improve human genetic
: diversity, or if it's even something we should worry about.

	Jacob Bronowski, in The Ascent of Man, said that we mate with
people we like.  He thought that this leads to the kinds of social
interactions which make man better fit.  I agree with his argument, and
would add that liking more kinds of people will lead both to better
fitness and a better society.
				Bill Tivol

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