If we look round the world, there seem to be not above six distinct varieties in the human species, each of which is strongly marked, and speaks the kind seldom to have mixed with any other. But there is nothing in the shape, nothing in the faculties, that shows their coming from different originals; and the varieties of climate, of nourishment, and custom, are sufficient to produce every change.

The Works of Oliver Goldsmith: With an Account of His Life and Writings (ed. 1806)