During a usenet debate, a Liberal advocate of race-mixing announced:
Ken's reponse:
In my first post, I cited scholarly definitions of "species" that in no way touch upon the ability to produce fertile progeny. You will notice that you have offered no scholarly citation to support your own definition. Nor will you find that any definition as clear, simple, and objective as what you have proposed has any acceptance within the life sciences. On the contrary, taxonomic classification, especially at the species level, is nuanced, subjective, and complicated.
You make no distinction between hybridity under natural conditions and hybridity under domestication. But I'm going to confine my discussion to hybridity under domestication for two reasons. First, you imply the mere ability to produce fertile offspring, not the natural propensity to do so; and copulation between dissimilar individuals is far more likely to occur under domestication than under natural conditions. Second, it would be more appropriate to the discussion of humans, since modern humans live in extreme conditions of domestication and many have become insensitive in their choice of sexual partners to a degree unknown among wild animals.
The European wolf (Canus lupus) and common jackal (C. aureus) can both mate with domestic dogs (C. familiaris) to produce a second generation of fertile hybrids. However, it is universally allowed today that C. lupus and C. aureus belong to different species. The ancestry of C. familiaris is not known with certainty.
Innumerable examples could be quoted of hybridity between species under captivity or domestication. The species of gulls (Larus) interbreed freely in captivity. In this genus, as in so many others, the normal mating behavior, which made divergent evolution possible, seems to be almost completely broken down by artificial conditions. [Schwidetzky, I. (edited by), 1962. Die neue Rassenkunde. Stuttgart (Fisher).]
The canary (Secinus canaria) has been mated with the citral finch (Carduelis citrinella). Although the crossing is intergensic, the offspring are fertile with the parent stocks and are capable of producing permanent stocks.
The fact that the domestic goat (Capra hircus) has been stated by reliable observers to hybridize in certain circumstances with the domestic sheep (Ovis aries) is particularly remarkable, on account of the marked differences between the members of these two forms, which cause them to be placed by taxonomists, not only in different genera, but in different subfamilies, the Caprinae and Ovinae. Apart from the external features that obviously separate them, there are many others in various parts of the body.
Therefore, the facts of human hybridity do not prove that all human races are to be regarded as a single species. The whole idea of species is vague because the word is used with such different meanings, none of which is of universal application. Those who go to great lengths to emphasize that "we are all the same species" are not actually engaging in a serious discussion of taxonomy, but actually seek to obscure the real racial differences upon which those classifications are based.
You ought to read _Race_ by John R. Baker, Oxford University Press. I relied heavily upon this book to write this article.