In the human species, the male is generative, at the longest, up
to seventy years, and the female up to fifty; but such extended
periods are rare. As a rule, the male is generative up to the age of
sixty-five, and to the age of forty-five the female is capable of
conception.

The ewe bears up to eight years, and, if she be carefully
tended, up to eleven years; in fact, the ram and the ewe are
sexually capable pretty well all their lives long. He-goats, if they
be fat, are more or less unserviceable for breeding; and this, by
the way, is the reason why country folk say of a vine when it stops
bearing that it is 'running the goat'. However, if an over-fat he-goat
be thinned down, he becomes sexually capable and generative.