With all the helps which written monuments afford, we do but faintly realize the condition of man two thousand or three thousand years ago.

Of what his condition was when removed to a distance 200,000 or 300,000 years, when the majority of mankind were lower and nearer the animals than any tribe now existing upon the earth, we cannot even entertain conjecture.

Plato (Laws) and Aristotle (Metaph.) may have been more right than we imagine in supposing that some forms of civilisation were discovered and lost several times over.

If we cannot argue that all barbarism is a degraded civilization, neither can we set any limits to the depth of degradation to which the human race may sink through war, disease, or isolation.
And if we are to draw inferences about the origin of marriage from the practice of barbarous nations, we should also consider the remoter analogy of the animals.

Many birds and animals, especially the carnivorous, have only one mate, and the love and care of offspring which seems to be natural is inconsistent with the primitive theory of marriage.