Donkey of Asiatic wild ass or onager, "Equus hemionus", and three subspecies of the kiang, "Equus kiang", of the Himalayan upland. A male donkey (jack) can be crossed with a female horse to produce a mule. A male horse can be crossed with a female donkey to produce a hinny. Horse-donkey hybrids are almost always sterile because horses have 64 chromosomes whereas donkeys have 62, producing offspring with 63 chromosomes. Mules are much more common than hinnies. This is believed to be caused by two factors, the first being proven in cat hybrids, that when the chromosome count of the male
Human male sexuality child they are raising is biologically theirs. Because of this difference, males have to adapt their own sexual strategies to accommodate the strategies of the females around them. Among other behaviors, this means that men are more likely to favour chastity in a woman, as this way a male can be more certain that her offspring are his own. Such a strategy is seen in males, and maternity is never doubted by the female, and so a chaste male is not highly valued by women. However, for men, female chastity confirms paternity, causing the male to compromise his sexual strategies