birth mean of the new generation is below the survival mean of the preceding generation; but in a species that is undergoing evolution the survival mean of the new generation, by reason of the great elimination of its unfit, is somewhat beyond the survival mean of the preceding generation, and thereby small variations shade in the progress of time into great differences. But never, or very rarely,—so rarely that if they ever occur examples of it are altogether unknown to us in nature,—does a specific change of type result from a great individual variation. Never do we see a wild animal possessed of an abnormality—i.e. a great variation—which affords to it such an advantage that it far transcends the rest of its species in the perfection of its adaptation to the environment; and most certainly never do we see a wild animal possessed of an abnormality so great, so favourable to survival, so advantageous in the struggle for existence, that as a result all competitors are exterminated, and the abnormality is imprinted on the race. In fact, as I have already said, "evolution proceeds not on lines of traits, however favourable, which occur infrequently or abnormally, but on lines of traits common to all the individuals of the whole species, that is, traits in which every individual rises or falls below the specific average." The Past Evolution of the races of men surely affords conclusive proof of this.[1]
- ↑ In the November number of the Nineteenth Century Review Mr. Herbert Spencer has some remarks on Lord Salisbury's Oxford speech which are curiously like my own. Mr. Spencer had of course not seen my manuscript, while, on the other hand, at the time his article appeared this book had long been in the hands of the publishers, and the passages in question had already been "set up" in type.
