The Great Apes
The great apes (Pongidae) are not nearly as human
as is sometimes supposed and as the problem-solving powers of the
chimpanzee might indicate. Physically they are very
different.
Their great weight has brought them to the lower
branches of the trees and to the ground, and they walk rather than
run on all fours, using their forelimbs as crutches, knuckles down.
The feet have lost their mobility and some of their prehensility.
The spine is massive and rigid, the shoulders broad, the chest
barrel-shaped and the arms enormously long. Their tails have been
entirely lost and their legs are short.
The heavy chewing and neck muscles are attached
to remarkable bony ridges along the top of the skull. The canine
teeth are well developed and the jaw pattern rather rectangular,
whereas that of man is semicircular. Their brains are well
developed, though far below those of Homo erectus.
We thus see that a considerable degree of
specialization has taken place, from which there can be no
return.
No evolution of the apes in the direction of man
is now possible. It is even correct to say that man is in many
respects closer to the monkeys than he is to the apes, especially
with regard to the generalized proportion of the hands, the
development of the thumb, the leg and foot muscles, the sequence of
eruption of the middle teeth, the tendency towards late
obliteration of the cranial sutures, and in the absence of a
curious long shelf just underneath the front of the jaw (also
absent in Proconsul). From this it would appear that the stock from
which the hominids arose was monkey-like rather than
ape-like.