Whether amongst anthropoids any instinctive avoidance prevails, preventing what we conceive of as incest, nobody knows. With their solitary families, the growth of such a disposition may be more difficult than amongst gregarious animals (such as our ancestors had become long before they could be called “human”), who find other families at hand to intermarry with; though the primitive human bands probably were not large. Savages now at the lowest level, such as the Veddas or Yaghans, rarely form parties of more than thirty or forty. The Boschmans, before their tribal habits were destroyed in the early years of last century, though sometimes assembling in large numbers for the great hunts by means of stockade traps, yet were usually scattered in groups of a few families. It is not likely that their remote forefathers consorted in larger numbers: eight or ten families may have been enough to co-operate in hunting, or in mutual defence. Within each family constituting such a band the tendency to Exogamy may first have manifested itself. Westermarck’s hypothesis concerning Exogamy was first published in the _History of Human Marriage_,[530] and has been re-stated in _The Origin and Development of Moral Ideas_.[531] In the former work he fully discusses the evidence as to the effects of the inter-breeding of near kin, and concludes that it is probably injurious. The evidence is conflicting, but his conclusion seems to me justifiable. And he rightly points out that if, amongst civilised nations, the mischief of inbreeding is not always manifest, it was probably much greater amongst primitive savages: (1) because the blood of the stock was purer; for in modern Europe (_e. g._) every marriage brings together many different strains. (2) Because communities were then much smaller; so that under endogamous conditions whatever vice may beset inbreeding would, generation after generation, be perpetuated and exaggerated without relief. It may be added that with Endogamy the young folk are likely to begin to breed earlier—perhaps by two or three years—than they would with Exogamy; and there is no doubt that the marriage of immature individuals is highly injurious to the race. But if inbreeding was injurious, Natural Selection favoured any family or band that practised Exogamy. That any should have done so on rational grounds, to avoid the observed evil effects of inbreeding, cannot be supposed. The motive must have been blind to the consequences, and may have taken the form of coldness toward those of opposite sex with whom one had grown up from infancy, or of aversion to the idea of marrying them. Such dispositions Natural Selection preserved, and they have descended to ourselves; for such was the beginning of the abhorrence of incest.