In the first place, history shows that wherever polygamy has been largely allowed the race has deteriorated.

One man to one woman is the law of God and nature.

Nearly all the civilized peoples of the world at some period before the age of written records, have become monogamists; and the step when once taken has never been retraced.

The exceptions occurring among Brahmins or Mahometans or the ancient Persians, are of that sort which may be said to prove the rule.

The connexions formed between superior and inferior races hardly ever produce a noble offspring, because they are licentious; and because the children in such cases usually despise the mother and are neglected by the father who is ashamed of them.
Barbarous nations when they are introduced by Europeans to vice die out; polygamist peoples either import and adopt children from other countries, or dwindle in numbers, or both.