species, the males are, on average, larger and stronger than the females, although the degree
of sexual dimorphism varies greatly. Most living species are predominantlyquadrupedal
(four-footed), but all are able to use their hands for gathering food or nesting materials, and
in some cases, for using tools, such as gorillas using sticks to gauge the depth of water and
chimpanzees sharpening sticks to use as spears in hunting and using sticks to gather food
and to “fish” for termites (Figure14.33).
Figure 14.32: A gorilla mother and baby, members of the great apes, at Volcans National
Park, Rwanda. The gorilla is the largest of the hominids, getting up to 309-397 lbs. ( 29 )
Most species are omnivorous (eat both plants and meat), but fruit is the preferred food
among all but humans. In contrast, humans consume a large proportion of highly processed,
low fiber foods, unusual proportions of grains and vertebrate meat, as well as a wide variety
of other foodstuffs. Human teeth and jaws are markedly smaller for our size than those of
other apes, perhaps as adaptations to eating cooked food. Humans may have been eating
cooked food for possibly as long as a million years or more.
Gestation lasts 8-9 months and usually results in the birth of a single offspring. The young
are born helpless, and thus they need parental care for long periods of time. Compared with
most other mammals, great apes have a long adolescence and become fully mature not until
8-13 years in most species (longer in humans). Thus, females typically give birth only once
every few years.
Gorillas and chimpanzees live in family groups of approximately five to ten individuals,
although larger groups are sometimes observed. The groups include at least one dominant
male, and females leave the group at maturity. Orangutans, however, are generally solitary.
Human social structure is complex and highly variable. Can you think of any that are similar
to those of other great apes?
Gorillas, chimpanzees and humans are all lumped together in the subfamily, the Homininae,