The Origin of Domesticated Animals

How could a layman possibly know when he first tamed an animal whether it would vary in succeeding generations? As the little variability of the ass and goose, or the small power of endurance of warmth by the reindeer, or the cold by the common camel, prevented their domestication. In the case of most of our anciently domesticated animals and plants, it is not possible to come any definite conclusion whether they are 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 times much diversity in the breeds. Some of these ancient breeds closely resemble, or are even identical