the leg shorter than in man himself, their
comparative length perhaps not differing greatly from that of the
chimpanzee. Aside from all other considerations, the use of the legs as
the sole organs of locomotion could not well fail to produce this
result, the legs growing longer and stronger in consequence of the
increased duty laid upon them, and the arms growing shorter and weaker
through their release from duty in locomotion. The case does not differ
in character from those of the dinosauria and the kangaroos, in both of
which instances a release of the arms from duty in walking was followed
by a considerable decrease in length and strength, while the legs grew
proportionally stronger.

If any disadvantage attended the shortening of the arms of the man-ape,
to the extent that this may have taken place in the tree, it was
probably correlated with some advantage. In the various instances of
short-armed animals cited this appears to have been the case, and it was
probably so in man's ancestral form. While the hands continued useful in
grasping and enabling the animal to maintain its place on the boughs,
they may have been gradually diverted to some other service, with the
result that the animal found the tree less desirable than before as a
place of residence and sought the ground instead. This would be
particularly the case if the new duty was one best exercised upon the
ground.

Shall we offer a suggestion as to this new use? Such changes are usually
the result of some change of habit in the animal, frequently one that
has to do with its food. Change of diet or of the mode of obtaining food
is the most potent influencing cause of change of habit in animals, and
the one that first calls for consideration.

The apes are frugivorous animals, though not exclusively so. Carnivorous
tendencies are displayed by many of them. They rob birds' nests of their
eggs and young, they capture and devour snakes and other small animals.
In zooelogical gardens monkeys are often observed to catch and eat mice.
It is evident that many of them might readily become carnivorous to a
large extent under suitable conditions. The large apes are usually
frugivorous, but some of them eat animal food. This is the case with
both the chimpanzee and the gorilla. The latter, while living usually on
fruit and often making havoc in the sugar-cane plantations and
rice-fields of the natives, also eats birds and their eggs, small
mammals and reptiles, an