THE AMERICAN
JOURNAL OF SOCIOLOGY
VOLUME XV JANUARY, 19 10 NUMBER 4
RACE AND MARRIAGE
PROFESSOR ULYSSES G. WEATHERLY Indiana University
The aversion exhibited by most animals to pairing with indi- viduals of another species has been attributed by Westermarck to the selective power of hereditary instinct. Those which prefer pairing with their own kind transmit their characteristics to their offspring and become the progenitors of numerous individuals marked by this particular trait. Hybrid kinds on the other hand have a smaller chance of survival, both because they are either sterile or relatively infertile, and because departure from type is not conducive to the favor of their fellows.^ Among plants, where conscious choice is impossible, hybrid individuals are more numerous. So clearly developed is this instinctive aversion among the higher vertebrates that certain varieties refuse to interbreed with closely related varieties of the same species. Examples of this occur among some kinds of deer, sheep, and horses. It is impossible to determine at what point in evolution the non-pairing instinct merges into a definite consciousness of kind, or when physical inability to cross is transformed into actual aversion to crossing, but it is certain that species aversion exists far down the scale of animal intelligence.
With the lowest orders of humans there enters another factor based on a highly developed self-sense which is found in animals only in a rudimentary form. Aversion to cross-breeding may
- Westermarck, History of Human Marriage, 280.
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