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ix LIMITS OF NATURAL SELECTION IN MAN 197the accumulation of variations from a hairy ancestor. Theevidence all goes to show that such variations could not havebeen useful, but must, on the contrary, have been to someextent hurtful. If even, owing to an unknown correlationwith other hurtful qualities, it had been abolished in theancestral tropical man, we cannot conceive that, as manspread into colder climates, it should not have returned underthe powerful influence of reversion to such a long persistentancestral type. But the very foundation of such a suppositionas this is untenable, for we cannot suppose that acharacter which, like hairiness, exists throughout the wholeof the mammalia, can have become, in one form only, soconstantly correlated with an injurious character as to lead toitspermanent suppression a suppression so complete andeffectual that it never, or scarcely ever, reappears in mongrelsof the most widely different races of man.Two characters could hardly be wider apart than the sizeand development of man's brain and the distribution of hairupon the surface of his body, yet they both lead us to thesame conclusion that some other power than natural selectionhas been engaged in his production.Feet and Hands of Man, considered as Difficulties onthe Theory of Natural SelectionThere are a few other physical characteristics of man thatmay just be mentioned as offering similar difficulties, thoughI do not attach the same importance to them as to those Ihave already dwelt on. The specialisation and perfection ofthe hands and feet of man seems difficult to account for.Throughout the whole of the quadrumana the foot is prehensile,and a very rigid selection must therefore have beenneeded to bring about that arrangement of the bones andmuscles which has converted the thumb into a great toe, socompletely, that the power of opposability is totally lost inevery race, whatever some travellers may vaguely assert tothe contrary.It is difficult to see why the prehensile powershould have been taken away. It must certainly have beenuseful in climbing, and the case of the baboons shows that itis quite compatible with terrestrial locomotion. It may notbe compatible with perfectly easy erect locomotion ; but, then,