> Fourthly, animals that have been evolving along separate paths for a million
> years (coyote and dog) can still form viable offspring. (Carles Vila et al,
> "Multiple and Ancient Origins of the Domestic Dog," Science, 276(June 13,
> 1997):1687-1689, p. 1689) Since Neanderthals and sapiens were separated for
> only about 300,000 years what exactly is the problem?
The relationship between interbreeding and genetic relationship is complex.
Recent studies on birds have suggested that some of the forms that produce
viable hybrids are less closely related than species not known to hybridize.
Two factors are involved. On the one hand, very distantly related species are
more likely to have genetic differences or possibly even physical differences
that prevent viable mating. On the other hand, very close but non-conspecific
relatives are most likely to be mistaken for potential mates and thus provide
the greatest evolutionary incentive for developing barriers to reproduction.
David C.
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