brain, to whose
great development man owes his superiority, the only marked difference
is in size. Structurally, the distinctions are unimportant. If, then,
these distant relatives so closely resemble man in physical frame, his
immediate relative in the line of descent must have approached him still
more closely in organization. After this ancestor had become a true,
surface-dwelling biped, the differences in structure were probably so
slight that physically the two forms were in effect identical. The
man-ape was, as there is reason to believe, considerably smaller than
man, perhaps about equal in size and stature to the chimpanzee, but
that does not constitute a specific difference. There may have been some
differences in the skeletal and muscular structure. The vocal organs,
for instance, probably differed, the evolution of language in man being
accompanied with certain changes in the larynx. The skull was certainly
much more ape-like. Yet variations of this kind, due to differences in
mode of life, are minor in importance, and may easily come within the
limits of a species. While the great features of organization remain
intact, small changes, due to new exigencies of life, may take place
without affecting the zooelogical position of an animal. The most
striking difference between man-ape and man, that of the development of
the brain to two or three times its size and weight, is similarly
unessential in classification while the brain remains unchanged in
structure. That it has remained unchanged we may safely deduce from the
close similarity between the brain of man and those of the existing
anthropoid apes. The cause of the increase in size is so evident that it
need only be referred to. Since the era of the man-ape, almost the whole
sum of the forces of development have been centred in the mental powers
of this animal, with the result that the brain has grown in size and
functional capacity, while the remainder of the body has remained
practically unchanged.

That man as an animal has descended from the lower life realm, none who
are familiar with the facts of science now think of denying. This has
attained to the scientist, and to many non-scientists, the level of a
self-evident proposition. But that man as a thinking being has descended
from the lower animals is a different matter, concerning which opinion
is by no means in unison. Even among scientists some degree of
difference of opinion exists, and such a radi