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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, ... it is not possible to come to any definite conclusion, whether they have descended from one or several wild 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? Since the recent discoveries of flint tools or celts in the superficial deposits of France and England, few geologists will doubt that man, in a sufficiently civilized state to have manufactured weapons, existed at a period extremely remote as measured by years; and we know that at the present day there is hardly a tribe so barbarous as not to have domesticated at least the dog.
The origin of most of our domestic animals will probably for ever remain vague. But I may here state, that looking to the domestic dogs of the whole world, I have, after a laborious collection of all known facts, come to the conclusion that several wild species of Canidæ have been tamed, and that their blood, more or less mingled,