ABSTRACT
No two humans are ever identical. We take so completely for granted that every person differs from every other that the similarity of identical twins (who are never really “identical”) strikes us as startling and peculiar. Individual variation exists, of course, in all biological species, but the realization that two identical flies are no more likely to exist than two identical humans comes as something of a surprise to non-biologists. Humans perceive differences among humans more easily than differences among flies. This legitimate anthropocentrism becomes troublesome in scientific studies of human and organic diversity. We tend to overvalue the magnitude of the differences in human materials relative to the differences found elsewhere.
