In what I just said I left an "almost." There is a great deal of
saving virtue in that little adverb. Doubtless even animals low in
the scale possess some faint traces of educability; but they are so
very slight that it takes geologic ages to produce an appreciable
result. In all the innumerable wanderings, fights, upturnings and
cataclysms of the earth's stupendous career, each creature has been
summoned under penalty of death to use what little wit he may have
had, and the slightest trace of mental flexibility is of such
priceless value in the struggle for existence that natural
selection must always have seized upon it, and sedulously hoarded
and transmitted it for coming generations to strengthen and
increase. With the lapse of geologic time the upper grades of
animal intelligence have doubtless been raised higher and higher
through natural selection. The warm-blooded mammals and birds of
to-day no doubt surpass the cold-blooded dinosaurs of the Jurassic
age in mental qualities as they surpass them in physical structure.
From the codfish and turtle of ancient family to the modern lion,
dog, and monkey, it is a very long step upward. The mental life of
a warm-blooded animal is a very different affair from that of
reptiles and fishes. A squirrel or a bear does a good many things
in the course of his life. He meets various vicissitudes in
various ways; he has adventures. The actions he performs are so
complex and so numerous that they are severally performed with less
frequency than the few actions performed by the codfish. The
requisite nervous connections are accordingly not fully established
before birth. There is not time enough. The nervous connections
needed for the visceral movements and for the few simple
instinctive actions get organized, and then the creature is born
before he has learned how to do all the things his parents could
do. A good many of his nervous connections are not yet formed,