Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!sdd.hp.com!hplabs!hpfcso!mll
From: mll@hpfcso.FC.HP.COM (Mark Luce)
Newsgroups: sci.bio
Subject: Re: Re: Humans and apes can(not?) be cross-fertilizated?
Message-ID: <9560007@hpfcso.FC.HP.COM>
Date: 14 Jun 91 16:12:03 GMT
References: <1991Jun13.221912.7336@cs.cmu.edu>
Organization: Hewlett-Packard, Fort Collins, CO, USA
Lines: 43

/ hpfcso:sci.bio / mtp@allwet.zso.dec.com (Michael T. Peterson) /  6:22 pm  Jun 13, 1991 /
     writes:
There are a host of reasons why Humans and Chimps are
unable to cross-breed.  Apart from the genetic differences,
there are substantial differences in the histocompatibility
complexes of each species.  Differences in these cell-surface
proteins, for example, may preclude the sperm of one species
from attaching and/or penetrating the egg of the other.

Another potential problem in this scenerio is the specific
binding of the protein complexes responsible for DNA
unwinding.  Chimp complexes may not recognize human DNA or
vice versa, or the rates at which the species' DNA was 
unwound and recombined may be so different as to preclude
proper recombination, etc., etc.

In point of fact, the specific variation in the sequences of
nucleotide bases probably has little to do with the potential
for successful breeding -- It's all the housekeeping that occurs
before, during, and after that probably exerts the more
significant effect.

By the way, one of the operational tests of speciation is
whether breeding can be successfully accomplished.  Said another
way, if A can breed with B, then A and B belong to the same
species.  If A can not, the A and B are of a different
species.

     This last paragraph, at least, is just plain wrong. Tigers and
lions are classified as separate species, yet they can interbreed to
produce 'tiglons' and 'ligers' (depending on whether the mother is a
tiger or a lion, respectively, although I may have this reversed).
Horses and donkeys are classifed as separate species but interbreed
to produce mules. The several species of the genus Canis can all
interbreed to produce fully interfertile offspring. The operational
test of speciation, I believe, is better described by asking whether
A typically can and does interbreed with B in the wild. Whether 
chimps and humans can be hybridized is something that, IMO, can only
be answered by experimentation.
regards,

/mtp
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