Re: "Species"? Feces!

Within any single group of animals, either the offspring are
reproductively compatible with their brethren, in which case they have
at least a theoretical chance of passing on their genes; or else they
are reproductively incompatible with their brethren, and they cannot
pass on their genes.
Mark Adkins
msadkins04@xxxxxxxxx

This is a false statement. The reproductive compatibility of an
individual with other individuals is to a large extent dependent on
variations inherited and expressed by the two individuals. An animal
with a certain trait can be more fertile with a mate that has the same
trait than with mate who does not share this traite. No single traite
by itself completely stops mutual compatibility. Variations that limit
compatibility can accumulate over time, eventually resulting in
complete reproductive isolation. However, the incompatibility would not
become complete for many generations.
An example of such a mutated variation would be the splitting of
a chromosome. When a chromosome in a gamete splits cleanly, the split
does not greatly change the chance that it will be fertilized by an
unchanged gamete. The enzymes that the original chromosome codes for
are still produced, except in the region close to the split. If the
split occurs at a region of noncoding DNA, the only changes may be in
terms of timing.
The resulting individual will have one more chromosome than its
parents. It may be slightly less compatible with the surrounding
population than unmutated members, but completely compatible with other
members that have the extra chromosome. The individual would with a
couple of generations have produced a number of offspring with the
extra chromosome. These individuals could mate with each other (no
problem), or with other members (with a slight disadvantage). The
variation associated with a split chromosome could be an advantage in
some environments.
Other variations also limit mating compatibility. Genital size,
table manners, blood type, etc. If a few such variations accumulate due
to natural selection, the incompatibility would accumulate resulting in
complete incompatibility. This barrier would determine new species
under some definitions.


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