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Re: Extinction scenarios
In a message dated 8/19/98 4:40:38 AM, Jaime A. Headden wrote:
<< The migration, of course, brings with it diseases, a scenario I have
always thought very much possible.>>
You have stepped onto the square where my credentials are strongest, and I
must (gently now, Tom) -- uh -- offer you some -- insight.
After twenty years in the biotech industry, and several patented vaccines
to my credit, I must urge you to abandon the "disease got them" tack. Quite
simply, no way.
There are two reasons why this old concept of dino extinction is no longer
taken seriously. As the human genome sequencing project started ten years or
so ago, one of the first chromosomal regions studied was the major
histocompatibility locus. To oversimplify, it shows a tremendous redundancy
of genes (many copies) whose sole purpose is to protect against disease.
Among these many genes there are many alleles (variations on the theme) that
give populations a great variation in their response capability to different
diseases, including forms of disease that the genes' owners HAVE NEVER SEEN
BEFORE. When a plague strikes (bubonic, black, smallpox etc.) even in an
immunologically naive population, there are always individuals who
"miraculously" are untouched. These individuals just happened to have a
histocompatibility allele that was resistent to the organism, and would
repopulate in a geological instant, and MOST of their progeny would be
resistant to the formerly "new" microbe.
Secondly, any organism that has perfected its ability to kill its host, by
killing one hundred percent of its victims, does not prevail. Rather, it
becomes extinct itself, due to the inability to be spread from one host to the
next (remember, the first host is dead). There is, therefore, a selective
pressure for inefficient killers to remain inefficient. Witness influenza and
the common cold, which are still very much with us, while bubonic plague, a
greater killer, is nearly extinct.
P.S. Not just humans, but chickens as well, have this sort of defense, so
guess who else did.