[157] But the primary idea of eating or drinking together as a bond of union was preserved, and can be recognised in religious and social custom to an advanced period of civilisation.
67.

The origin of exogamy.
Again, Dr.Westermarck shows that the practice of exogamy or the avoidance of intermarriage did not at first arise between persons recognised as blood relations, but between those who lived together.

"Facts show that the extent to which relatives are not allowed to intermarry is nearly connected with their close living together.

Generally speaking the prohibited degrees are extended much further among savage and barbarous peoples than in civilised societies.

As a rule the former, if they have not remained in the most primitive social condition of man, live not in separate families but in large households or communities, all the members of which dwell in very close contact with each other." [158] And later, after adducing the evil results of self-fertilisation in plants and close interbreeding in animals, Dr.Westermarck continues: "Taking all these facts into consideration, I cannot but believe that consanguineous marriages, in some way or other, are more or less detrimental to the species.