It may at first sight seem strange that all the characteristics, however slight, in which the various races of men differ from each other, should harmonize with particular conditions of life to the exclusion of others. But it must be remembered that, if we had fuller knowledge, characteristics which seem to us useless, or even hurtful, might be seen to be useful. We know the utility of _some_ special characteristics, and that of others may, at least provisionally, be assumed. It is certain that the physiological functions of most persons who quit their native land and settle in a wholly different region, must undergo a considerable change if the new conditions are not to have injurious effects. Moreover, many bodily structures are so intimately related, that when one part varies others vary also, though, in most instances, we are quite unable to assign any reason why this should be the case. Savage men are generally distinguished for relatively large jaws, which, no doubt, are of use in a state of nature, where food is often hard and tough, where the jaws have to perform the functions of knife and fork, and where the teeth occasionally serve as implements. This racial peculiarity, being in fact only a mark of low civilization, is thus easily accounted for by the law of natural selection. The less man, with advancing civilization, was in want of large and strong jaws, the greater was the chance for individuals born with smaller jaws to survive; hence a race with comparatively small jaws gradually arose. Indeed, Professor Virchow has shown that the prognathous type of face is inconsistent with the full development of the brain.[1586] Another peculiarity which characterizes the lower races of men is the lateral jutting-out of the cheek-bones. But, as Mr. Spencer observes, this excessive size of the cheek-bones is only an accompaniment of large jaws. Other peculiarities of feature—depression of the bridge of the nose, forward opening of the nostrils, wide-spread _alæ_, and a long and large mouth—constantly coexist with large and protuberant jaws and great cheek-bones, alike in uncivilized races and in the young of civilized races;[1587] hence we cannot believe that the connection is merely accidental.