ins,[519] and the breed has
lately split into two strains--one strain having a white face, and
differing slightly, it is said,[520] in some other points; but there is no
reason to believe that this split, the origin of which is unknown, was
intentionally made; it may with much more probability be attributed to
different breeders having attended to different points. So again, the
Berkshire breed of swine in the year 1810 had greatly changed from what it
had been in 1780; and since 1810 at least two distinct sub-breeds have
borne this same name.[521] When we bear in mind how rapidly all animals
increase, and that some must be annually slaughtered and some saved for
breeding, then, if the same breeder during a long course of years
deliberately settles which shall be saved and which shall be killed, it is
almost inevitable that his individual frame of mind will influence the
character of his stock, without his having had any intention to modify the
breed or form a new strain.

Unconscious selection in the strictest sense of the word, that is, the
saving of the more useful animals and the neglect or slaughter of the less
useful, without any thought of the future, must have gone on occasionally
from the remotest period and amongst the most barbarous nations. Savages
often suffer from famines, and are sometimes expelled by war from their own
homes. In such cases it can hardly be doubted that they would save their
most useful animals. When the Fuegians {215} are hard pressed by want, they
kill their old women for food rather than their dogs; for, as we were
assured, "old women no use--dogs catch otters." The same sound sense would
surely lead them to preserve their more useful dogs when still harder
pressed by famine. Mr. Oldfield, who has seen so much of the aborigines of
Australia, informs me that "they are all very glad to get a European
kangaroo dog, and several instances have been known of the father killing
his own infant that the mother might suckle the much-prized puppy."
Different kinds of dogs would be useful to the Australian for hunting
opossums and kangaroos, and to the Fuegian for catching fish and otters;
and the occasional preservation in the two countries of the most useful
animals would ultimately lead to the formation of two widely distinct
breeds.

* * * * *

With plants, from the earliest dawn of civilisation, the best variety which
at each period was known would generally h