devolution that may work downward till very many of the fundamental
activities are lost before death.

Nothing better illustrates this distinction than the difference
between the fore foot of animals and the human hand. The first begins
as a fin or paddle or is armed with a hoof, and is used solely for
locomotion. Some carnivora with claws use the fore limb also for
holding well as tearing, and others for digging. Arboreal life seems
to have almost created the simian hand and to have wrought a
revolution in the form and use of the forearm and its accessory
organs, the fingers. Apes and other tree-climbing creatures must not
only adjust their prehensile organ to a wide variety of distances and
sizes of branches, but must use the hands more or less freely for
picking, transporting, and eating fruit; and this has probably been a
prime factor in lifting man to the erect position, without which human
intelligence as we know it could have hardly been possible. "When we
attempt to measure the gap between man and the lower animals in terms
of the form of movement, the wonder is no less great than when we use
the term of mentality."[3] The degree of approximation to human
intelligence in anthropoid animals follows very closely the degree of
approximation to human movements.

The gradual acquirement of the erect position by the human infant
admirably repeats this long phylogenetic evolution.[4] At first the
limbs are of almost no use in locomotion, but the fundamental trunk
muscles with those that move the large joints are more or less
spasmodically active. Then comes creeping, with use of the hip
muscles, while all below the knee is useless, as also are the fingers.
Slowly the leg and foot are degraded to locomotion, slowly the great
toe becomes more limited in its action, the thumb increases in