Re: Clarification on relationship between Morphology and genes
Tom Tadfor Little (tlittle@lanl.gov)
Tue, 16 Jul 1996 15:02:40 -0600
Ricky Ferrell wrote:
> In case you are interested on
> the specific source of my confusion, I quote below from an article
> written by James Shreeve which appeared in Discover, Nov. 1994.
> "..the vast majority of human genetic variation occurs within
> populations, not between them, with only 6 percent accounted for
> by race, according to a classic study done in 1972 by geneticist
> Richard Lewontin of Harvard." (Discover, Nov. 1994)
>
Ah!
This statement says nothing about what percentage of the human
genome differs between individuals in our species. The 6% is
a fraction of the total *variation*, which is itself very small
in comparison with the total genome.
What the article is saying is that the traditional concept of
"race" is relatively ineffectual in capturing the genetic
differences between individuals or populations. (This is one
of the reasons the concept has been rejected by science in
this century.)
This kind of data is obtained by studying a selection of genes
known to have different alleles in humans (blood type, for example).
The genes selected are just those we happen to have practical
tests for; no attempt is made to systematically sample the human
genome.
The bottom line is that most alleles are present in
most human populations, with somewhat different frequencies in
different populations. Two individuals from the same population
may differ a great deal in which of those alleles they possess--
in fact they may differ as much as two people selected from
opposite ends of the globe.
I hope this makes things clearer!
--
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Tom Tadfor Little tlittle@lanl.gov -or- telp@Rt66.com
technical writer/editor Los Alamos National Laboratory
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Telperion Productions http://www.rt66.com/~telp/
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