"Educability" is the quality which distinguishes the brain of increased size. Dogs are more "educable" than rabbits; monkeys more so than dogs; and men more so--vastly more so--than monkeys and apes. The human infant is born with a few inherited mechanisms of "instinct," such as that which causes it to find its mother's nipple and to suck it, and to cling and support its own weight as no full-grown child can do. It is singularly free from any large number of inherited "instincts," and, to its own great advantage, has, during the many years in which it is protected by its parents, to learn everything and to construct new brain mechanisms--the results of "education" of the individual. We here use the word "education" in its proper and widest sense.
Thus we get an indication of "the reason why" the modern rhinoceros has a brain eight times as big as the titanotherium's. It is more "educable." The ancestors of our modern armour-plated friend have been surviving and beating their less "educable" brothers and sisters and cousins through a vast geological lapse of time; and the brains of the survivors have always been bigger, and they have become more educable and more educated until the race has culminated in those models of "sweet reasonableness," the modern rhinoceroses! It must be confessed that this character attributed to the rhinoceros is a matter of inference and not of direct observation of that animal when under his native sky. We do not judge the survivor of a fine early Miocene family by the fury and annoyance he shows when shot at, nor by the stolid contempt with which he treats mankind at the Zoo. The same signification--"educability"--attaches to the large brain of the higher apes; and man's still larger brain means still greater educability and resulting reasonableness.
In order that natural selection and the survival of the fittest should have led to this increased size and accompanying educability of the brain, it is necessary to suppose that the individuals with the more educable brain as they appeared profited by it, that is to say, did become more educated, and so defeated their rivals, and survived and transmitted their increased size of brain little by little in succeeding generations. There is no difficulty about admitting this supposition in regard to the passage from higher ape-like creatures to later forms having a full-sized brain, such as we find in the Neanderthal man and in some Australians. But we are met here by what looks, at first sight, as a fact inconsistent with our view. The obvious increased educability and consequent increased education of lower races of man by the circumstances of their lives, places them clearly enough in a position of great advantage over the higher surviving apes. But when we compare the actual mental accomplishments of the highest civilized races of man with those of big-brained savages, we find that a large proportion of individuals in the civilized races are much farther ahead of the lower savage races than most of these are ahead of the higher apes. Newton, Shakespeare, and Darwin are in mental accomplishment farther away from an Australian black, or even a Congo negro, than these "savages" are from a gorilla or a chimpanzee. Yet the difference when we compare the size and the abundance of the convolutions of the brain of the European philosopher and the black-fellow does not seem, superficially, to be proportionate to the difference in the mental performance of the two. No minute study of the microscopic differences in the structure of the two brains has, as yet, been made, and it is probable that there is a greater difference here than in the mere shape of the brain-mass. It seems that the "educability" of the brain measured by its size is little greater in the one group of men than in the other. And it is found--so far as observation and experiment have been carried--that individual savages belonging to races showing very low mental accomplishments in their native surroundings are yet capable of being "educated" to a far higher level of mental performance, when removed in early youth from their natural conditions and subjected to the same conditions as the better-cared-for children of a civilized race, than any of them ever reach in their own communities.