🚀 go-pugleaf

In article <674@intvax.UUCP> morimoto@intvax.UUCP (Alan Morimoto) writes:
>  My point is that maybe
>we need to look at what long term effects we are creating by breeding
>diseases into our future generations.  I can imagine that countries that are
>not as medically advanced inherit a stronger gene pool of people simply
>because the weak will perish.  Will the future of the world be inherited by
>us, the medically pampered, or the third world?

I am afraid I don't know what you're talking about.  When I got
vaccinated against polio, I was given a substance that forced my body
to develop a lifelong immunity to polio.  Because of the way the
immune system works, this immunity can not be passed to my children
(except for passive maternal antibodies should I breast feed -- this
immunity lasts a couple years at best), so they too will have to be
vaccinated against this and a small host of other diseases.  There is
no breeding for weakness there.  

If you're referring to the general concept that "less fit" people who
would die of childhood diseases are able (due to the miracles of
modern medicine) to survive to reproduce, hence breeding their
worthless and weak genes into future generations, all I can say is
that you are vastly oversimplifying things.  What about diseases that
kill people after they have successfully reproduced?  What about
childhood diseases that are not normally fatal in themselves but can
have serious sequelae later in life?  And, of course, what about
diseases that don't impair the ability of the afflicted to survive to
reproduce (like, say, oral herpes)?  

Another problem with the "natural selection says sick folks should
die" argument is that the environment can change for us much more
rapidly than evolution can deal with.  Remember, your average
Galapagos finch species lives for millenia on a little island where
the seasons don't change much, the other creatures don't change much,
the food doesn't change much, etc.  Over that extremely large number
of generations, those finches get a chance to try out and select for
or against a large number of mutations.  Because the environment is
relatively stable, or at worst changes only gradually, the same kinds
of things are likely to be selected for over many generations.  If
every five years, the bugs and the seeds changed size, say, then their
beaks wouldn't get a chance to evolve to an optimal size and shape.
Now, we people change our environment.  We move around, we build
things, etc.  What is advantageous in one environment may be dangerous
in another.  The best example I can think of offhand deals with 
sickle-cell anemia.  It's a genetic disease in which hemoglobin (the
protein in your blood that binds oxygen) has a mistake, so under
certain conditions, the red blood cells shrink up into these little
sickle shapes.  It's not really a terrible disease, as long as you're
not homozygous for it, but then again, it's not a good one either.
The odd thing about it is that being heterozygous for sickle-cell
anemia gives you a certain resistance to an infectious disease,
malaria.  Malaria is an acute illness and can kill you.  In parts of
Africa where malaria ran rampant because the environment was warm and
damp enough to support the mosquitoes that carry malaria, surprise,
surprise, sickle-cell anemia was selected for.  When those folks moved
to cooler climates or learned how to make mosquito netting or
whatever, malaria was no longer such a danger.  But they still had
sickle-cell anemia, and still passed it on to their offspring.
Whoops.

--Aimee

-- 
Aimee Yermish				ayermish@asylum.sf.ca.us
Program in Cancer Biology		ayermish@portia.stanford.edu
Stanford University			415-594-9268