Re: diseases and immunity
Mary Beth Williams (mbwillia@ix.netcom.com(Mary)
4 Jul 1996 12:01:08 GMT
In <31DB260D.78DE@best.com> Joel and Lynn Gazis-Sax <gazissax@best.com>
writes:
>* That Europeans were exposed to many infectious diseases at an
>earlier period than the peoples of the Americas.
>
>* That this exposure weeded out those less able to withstand the
>diseases and caused European populations to become more resistant to
>them.
Actually, this is both true and false. Yes, the exposure weeded out
those more suseptible to these diseases -- they died. However, those
people who actually fell victim to the diseases and survived became
*resistant* to such only because of the development of immunity through
prior first-hand exposure, not genetic mutation. Its already been
discussed that transfer of maternal immunity only lasts for the period
during breastfeeding (hence, the high mortality of post-weening
toddlers.) One of the reasons plague was less *successful* in
subsequent epidemics is that it didn't have *virgin* populations
through which to pass -- if it hit a pocket of *resistees*, and
couldn't thus be transmitted, it died out. This is one of the reasons,
as discussed previously, the smallpox probably didn't often make it
across the Atlantic until its vector of transmission (kids and/or other
non-resistees) increased.
MB Williams
Dept. of Anthro., UMass-Amherst
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