_The Chief Cause of Man's lengthened Infancy_
The reason for this is that any creature's ability to perceive and to
act depends upon the registration of experiences in his nerve-centres.
It is either individual or ancestral experience that is thus registered;
or, strictly speaking, it is both. It is of the first importance that
this point should be clearly understood, and therefore a few words of
elementary explanation will not be superfluous.
When you learn to play the piano, you gradually establish innumerable
associations between printed groups of notes and the corresponding keys
on the key-board, and you also train the fingers to execute a vast
number of rapid and complicated motions. The process is full of
difficulty, and involves endless repetition. After some years perhaps
you can play at sight and with almost automatic ease a polonaise of
Liszt or a ballad of Chopin. Now this result is possible only because of
a bodily change which has taken place in you. Countless molecular
alterations have been wrought in the structure of sundry nerves and
muscles, especially in the gray matter of sundry ganglia, or
nerve-centres. Every ganglion concerned in the needful adjustments of
eyes and fingers and wrists, or in the perception of musical sounds, has
undergone a change more or less profound. The nature of the change is
largely a matter of speculation; but that point need not in any way
concern us. It is enough for us to know that there is such a change, and
that it is a registration of experiences. The pianist has registered in
the intimate structure of his nervous system a world of experiences
entirely foreign to persons unfamiliar with the piano; and upon this
registration his capacity depends.
Now the same explanation applies to all bodily movements whatever,
whether complicated or simple. In writing, in walking, in talking, we
are making use of nervous registrations that have been brought about by
an accumulation of experiences. To pick up a pencil from the table may
seem a very simple act, yet a baby cannot do it. It has been made
possible only by the education of the eyes, of the muscles that move the
eyes, of the arm and hand, and of the nerve-centres that coordinate one
group of movements with another. All this multiform education has
consisted in a gradual registration of experiences. In like manner all
the actions of man upon the world about him are made up of movements,
and every such movement becomes possible only when a registration is
effected in sundry nerve-centres.
But this is not the whole story. The case is undoubtedly the same with
those visceral movements, involuntary and in great part unconscious,
which sustain life; the beating of the heart, the expansion and
contraction of the lungs, the slight changes of calibre in the
blood-vessels, even the movements of secretion that take place in
glands. All these actions are governed by nerves, and these nerves have
had to be educated to their work. This education has been a registration
of experiences chiefly ancestral, throughout an enormous past,
practically since the beginnings of vertebrate life.
With the earlier and simpler forms of animal existence these visceral
movements are the only ones, or almost the only ones, that have to be
made. Presently the movements of limbs and sense organs come to be
added, and as we rise in the animal scale, these movements come to be
endlessly various and complex, and by and by implicate the nervous
system more and more deeply in complex acts of perception, memory,
reasoning, and volition. Obviously, therefore, in the development of the
individual organism the demands of the nervous system upon the vital
energies concerned in growth must come to be of paramount importance,
and in providing for them the entire embryonic life must be most
profoundly and variously affected. Though we may be unable to follow the
processes in detail, the truth of this general statement is plain and
undeniable.
I say, then, that when a creature's intelligence is low, and its
experience very meagre, consisting of a few simple perceptions and acts
that occur throughout life with monotonous regularity, all the
registration of this experience gets effected in the nerve-centres of
its offspring before birth, and they come into the world fully equipped
for the battle of life, like the snapping turtle, which snaps with
decisive vigour as soon as it emerges from the egg. Nothing is left
plastic to be finished after birth, and so the life of each generation
is almost an exact repetition of its predecessor. But when a creature's
intelligence is high, and its experience varied and complicated, the
registration of all this experience in the nerve-centres of its
offspring does not get accomplished before birth. There is not time
enough. The most important registrations, such as those needed for
breathing and swallowing and other indispensable acts, are fully
effected; others, such as those needed for handling and walking, are but
partially effected; others, such as those involved in the recognition of
creatures not important as enemies or prey, are left still further from
completion. Much is left to be done by individual experience after
birth. The animal, when first born, is a baby dependent upon its
mother's care. At the same time its intelligence is far more plastic,
and it remains far more teachable, than the lower animal that has no
babyhood. Dogs and horses, lions and elephants, often increase in
sagacity until late in life; and so do apes, which, along with a higher
intelligence than any other dumb animals, have a much longer babyhood.
We are now prepared to appreciate the marvellous beauty of Nature's
work in bringing Man upon the scene. Nowhere is there any breach of
continuity in the cosmic process. First we have natural selection at
work throughout the organic world, bringing forth millions of species of
plant and animal, seizing upon every advantage, physical or mental, that
enables any species to survive in the universal struggle. So far as any
outward observer, back in the Cretaceous or early Eocene periods, could
surmise, this sort of confusion might go on forever. But all at once,
perhaps somewhere in the upper Eocene or lower Miocene, it appears that
among the primates, a newly developing family already distinguished for
prehensile capabilities, one genus is beginning to sustain itself more
by mental craft and shiftiness than by any physical characteristic.
Forthwith does natural selection seize upon any and every advantageous
variation in this craft and shiftiness, until this favoured genus of
primates, this _Homo Alalus_, or speechless man, as we may call him,
becomes preŰminent for sagacity, as the mammoth is preŰminent for bulk,
or the giraffe for length of neck.
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