The Origin of Infancy.
But before we can fully understand the exalted position which the
Darwinian theory assigns to man, another point demands consideration.
The natural selection of psychical peculiarities does not alone account
for the origin of Man, or explain his most signal difference from all
other animals. That difference is unquestionably a difference in kind,
but in saying this one must guard against misunderstanding. Not only in
the world of organic life, but throughout the known universe, the
doctrine of evolution regards differences in kind as due to the gradual
accumulation of differences in degree. To cite a very simple case, what
differences of kind can be more striking than the differences between a
nebula, a sun, a planet like the earth, and a planet like our moon? Yet
these things are simply examples of cosmical matter at four different
stages of cooling. The physical differences between steam, water, and
ice afford a more familiar example. In the organic world the perpetual
modification of structures that has been effected through natural
selection exhibits countless instances of differences in kind which have
risen from the accumulation of differences in degree. No one would
hesitate to call a horse's hoof different in kind from a cat's paw; and
yet the horse's lower leg and hoof are undoubtedly developed from a
five-toed paw. The most signal differences in kind are wont to arise
when organs originally developed for a certain purpose come to be
applied to a very different purpose, as that change of the fish's
air-bladder into a lung which accompanied the first development of land
vertebrates. But still greater becomes the revolution when a certain
process goes on Until it sets going a number of other processes,
unlocking series after series of causal agencies until a vast and
complicated result is reached, such as could by no possibility have been
foreseen. The creation of Man was one of these vast and complicated
results due to the unlocking of various series of causal agencies; and
it was the beginning of a deeper and mightier difference in kind than
any that slowly evolving Nature had yet witnessed.
I have indicated, as the moment at which the creation of mankind began,
the moment when psychical variations became of so much more use to our
ancestors than physical variations that they were seized and enhanced by
natural selection, to the comparative neglect of the latter. Increase of
intellectual capacity, in connection with the developing brain of a
single race of creatures, now became the chief work of natural selection
in originating Man; and this, I say, was the opening of a new chapter,
the last and most wonderful chapter, in the history of creation. But the
increasing intelligence and enlarged experience of half-human man now
set in motion a new series of changes which greatly complicated the
matter. In order to understand these changes, we must consider for a
moment one very important characteristic of developing intelligence.
The simplest actions in which the nervous system is concerned are what
we call reflex actions. All the visceral actions which keep us alive
from moment to moment, the movements of the heart and lungs, the
contractions of arteries, the secretions of glands, the digestive
operations of the stomach and liver, belong to the class of reflex
actions. Throughout the animal world these acts are repeated, with
little or no variation, from birth until death, and the tendency to
perform them is completely organized in the nervous system before birth.
Every animal breathes and digests as well at the beginning of his life
as he ever does. Contact with air and food is all that is needed, and
there is nothing to be learned. These actions, though they are performed
by the nervous system, we do not class as psychical, because they are
nearly or quite unattended by consciousness. The psychical life of the
lowest animals consists of a few simple acts directed toward the
securing of food and the avoidance of danger, and these acts we are in
the habit of classing as instinctive. They are so simple, so few, and so
often repeated, that the tendency to perform them is completely
organized in the nervous system before birth. The animal takes care of
himself as soon as he begins to live. He has nothing to learn, and his
career is a simple repetition of the careers of countless ancestors.
With him heredity is everything, and his individual experience is next
to nothing.
As we ascend the animal scale till we come to the higher birds and
mammals, we find a very interesting and remarkable change beginning. The
general increase of intelligence involves an increasing variety and
complication of experiences. The acts which the animal performs in the
course of its life become far more numerous, far more various, and far
more complex. They are therefore severally repeated with less frequency
in the lifetime of each individual. Consequently the tendency to perform
them is not completely organized in the nervous system of the offspring
before birth. The short period of ante-natal existence does not afford
time enough for the organization of so many and such complex habitudes
and capacities. The process which in the lower animals is completed
before birth is in the higher animals left to be completed after birth.
When the creature begins its life it is not completely organized.
Instead of the power of doing all the things which its parents did, it
starts with the power of doing only some few of them; for the rest it
has only latent capacities which need to be brought out by its
individual experience after birth. In other words, it begins its
separate life not as a matured creature, but as an infant which needs
for a time to be watched and helped.