little variability of the ass or guinea-fowl, or the small power of
endurance of warmth by the rein-deer, or of cold by the common camel,
prevented their domestication? I cannot doubt that if other animals
and plants, equal in number to our domesticated productions, and
belonging to equally diverse classes and countries, were taken from a
state of nature, and could be made to breed for an equal number of
generations under domestication, they would vary on an average as
largely as the parent species of our existing domesticated productions
have varied.

In the case of most of our anciently domesticated animals and plants,
I do not think it is possible to come to any definite conclusion,
whether they have descended from one or several species. The argument
mainly relied on by those who believe in the multiple origin of our
domestic animals is, that we find in the most ancient records, more
especially on the monuments of Egypt, much diversity in the breeds;
and that some of the breeds closely resemble, perhaps are identical
with, those still existing. Even if this latter fact were found more
strictly and generally true than seems to me to be the case, what does
it show, but that some of our breeds originated there, four or five
thousand years ago? But Mr. Horner's researches have rendered it in
some degree probable that man sufficiently civilized to have
manufactured pottery existed in the valley of the Nile thirteen or
fourteen thousand years ago; and who will pretend to say how long
before these ancient periods, savages, like those of Tierra del Fuego
or Australia, who possess a semi-domestic dog, may not have existed in
Egypt?

The whole subject must, I think, remain vague; nevertheless, I may,
without here entering on any details, state that, from geographical