Lengthening of Infancy, and Concomitant Increase of Brain-Surface

The Destiny of Man
by John Fiske

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VI.

The first appearance of infancy in the animal world thus heralded the new era which was to be crowned by the development of Man. With the beginnings of infancy there came the first dawning of a conscious life similar in nature to the conscious life of human beings, and there came, moreover, on the part of parents, the beginning of feelings and actions not purely self-regarding. But still more, the period of infancy was a period of plasticity. The career of each individual being no longer wholly predetermined by the careers of its ancestors, it began to become teachable. Individuality of character also became possible at the same time, and for the same reason. All birds and mammals which take care of their young are teachable, though in very various degrees, and all in like manner show individual peculiarities of disposition, though in most cases these are slight and inconspicuous. In dogs, horses, and apes there is marked teachableness, and there are also marked differences in individual character.

But in the non-human animal world all these phenomena are but slightly developed. They are but the dim adumbrations of what was by and by to bloom forth in the human race. They can scarcely be said to have served as a prophecy of the revolution that was to come. One generation of dumb beasts is after all very like another, and from studying the careers of the mastodon, the hipparion, the sabre-toothed lion, or even the dryopithecus, an observer in the Miocene age could never have foreseen the possibility of a creature endowed with such a boundless capacity of progress as the modern Man. Nevertheless, however dimly suggestive was this group of phenomena, it contained the germ of all that is preëminent in humanity. In the direct line of our ancestry it only needed that the period of infancy should be sufficiently prolonged, in order that a creature should at length appear, endowed with the teachableness, the individuality, and the capacity for progress which are the peculiar prerogatives of fully-developed Man. In this direct line the manlike apes of Africa and the Indian Archipelago have advanced far beyond the mammalian world in general.

Along with a cerebral surface, and an accompanying intelligence, far greater than that of other mammals, these tailless apes begin life as helpless babies, and are unable to walk, to feed themselves, or to grasp objects with precision until they are two or three months old. These apes have thus advanced a little way upon the peculiar road which our half-human forefathers began to travel as soon as psychical variations came to be of more use to the species than variations in bodily structure. The gulf by which the lowest known man is separated from the highest known ape consists in the great increase of his cerebral surface, with the accompanying intelligence, and in the very long duration of his infancy. These two things have gone hand in hand. The increase of cerebral surface, due to the working of natural selection in this direction alone, has entailed a vast increase in the amount of cerebral organization that must be left to be completed after birth, and thus has prolonged the period of infancy. And conversely the prolonging of the plastic period of infancy, entailing a vast increase in teachableness and versatility, has contributed to the further enlargement of the cerebral surface. The mutual reaction of these two groups of facts must have gone on for an enormous length of time since man began thus diverging from his simian brethren. It is not likely that less than a million years have elapsed since the first page of this new chapter in the history of creation was opened: it is probable that the time has been much longer. In comparison with such a period, the whole recorded duration of human history shrinks into nothingness.

The pyramids of Egypt seem like things of yesterday when we think of the Cave-Men of western Europe in the glacial period, who scratched pictures of mammoths on pieces of reindeer-antler with a bit of pointed flint. Yet during an entire geologic æon before these Cave-Men appeared on the scene, "a being erect upon two legs," if we may quote from Serjeant Buzfuz, "and wearing the outward semblance of a man and not of a monster," wandered hither and thither over the face of the earth, setting his mark upon it as no other creature yet had done, leaving behind him innumerable tell-tale remnants of his fierce and squalid existence, yet too scantily endowed with wit to make any written disclosure of his thoughts and deeds. If the physiological annals of that long and weary time could now be unrolled before us, the principal fact which we should discern, dominating all other facts in interest and significance, would be that mutual reaction between increase of cerebral surface and lengthening of babyhood which I have here described.

Thus through the simple continuance and interaction of processes that began far back in the world of warm-blooded animals, we get at last a creature essentially different from all others. Through the complication of effects the heaping up of minute differences in degree has ended in bringing forth a difference in kind. In the human organism physical variation has well-nigh stopped, or is confined to insignificant features, save in the grey surface of the cerebrum. The work of cerebral organization is chiefly completed after birth, as we see by contrasting the smooth ape-like brain-surface of the new-born child with the deeply-furrowed and myriad-seamed surface of the adult civilized brain. The plastic period of adolescence, lengthened in civilized man until it has come to cover more than one third of his lifetime, is thus the guaranty of his boundless progressiveness. Inherited tendencies and aptitudes still form the foundations of character; but individual experience has come to count as an enormous factor in modifying the career of mankind from generation to generation. It is not too much to say that the difference between man and all other living creatures, in respect of teachableness, progressiveness, and individuality of character, surpasses all other differences of kind that are known to exist in the universe.

Boston, Houghton, Mifflin And Company, 1893
Copyright, 1884 by John Fiske

About the Author

John Fiske (1842 - 1901), born Edmund Fisk Green, was an American philosopher and historian. He was born at Hartford, Conn., March 30, 1842. On the second marriage of his mother he assumed the name of his maternal great-grandfather, John Fiske. As a child, he exhibited remarkable precocity. He graduated from Harvard College in 1863 and at the Harvard Law School in 1865.