Ape diversity

The first apes evolved about 25 million years ago and by 20 million years ago were a very diverse group. Within the last 10 million years, however, many ape species became extinct as the earth’s climate cooled and dried and their forested environments changed to woodland and grassland. There are now only about 20 living species of apes and they are divided into two major groups. These are the:

Lesser Apes, containing the gibbons

Great Apes, containing the orang-utans, gorillas, chimpanzees and humans

Ape features

Apes (including humans) possess the same general features that all primates share but they differ from other primates in a number of distinctive ways.

Features that separate the apes from other groups of primates include:

a brain that is larger and more complex than other primates

distinctive molar teeth in the lower jaw which have a ‘Y5’ pattern (five cusps or raised bumps arranged in a Y-shape)

a shoulder and arm structure that enables the arms to freely rotate around the shoulder

a ribcage that forms a wide but shallow chest

an appendix

no external tail

The Lesser Apes

There are about 14 species of relatively small-bodied apes known as Lesser Apes. These are the gibbons, which live in trees, rarely descend to the ground and are active during the day. Gibbons are found in the forests of South-east Asia.

The gibbons have the following features:

body size which is similar in males and females

bodies adapted for living in trees which they rarely leave. These adaptations include very long arms with a shoulder structure that enables them to rapidly swing from one branch to the next and long curved finger and toe bones to powerfully grip tree branches

hardened pads of skin (callosites) on their buttocks for prolonged sitting

a diet of fruit or leaves

long, pointed canine teeth and long jaws

a social lifestyle consisting of small family groups consisting of an adult male-female pair and their juvenile offspring

The Great Apes

The Great Apes are named for their large bodies. They also have larger brains than other primates. Like Lesser Apes, the Great Apes are active during the day. There are four types of Great Apes – the orang-utans, gorillas, chimpanzees and humans.

Orang-utans

There are two living species of orang-utan – the Bornean Orang-utan, Pongo pygmaeus, and the Sumatran Orang-utan, Pongo abelii. Orang-utans live in dense rainforests of Borneo and Sumatra in South-east Asia.

Orang-utans have the following features:

considerable sexual dimorphism in which the males are about twice as big as the females

bodies adapted for living in trees which they rarely leave and also for quadrupedal (four-legged) movement on the ground. These adaptations include very long arms with a shoulder structure that enables them to move slowly from branch to branch (especially in young, lighter bodied orang-utans) and long curved finger and toe bones to powerfully grip tree branches

a diet of fruit supplemented by insects

long, pointed canine teeth and long jaws

occasional use of tools, such as twigs and sticks

a solitary lifestyle except when breeding or when mothers have offspring

Gorillas

There are two living species of gorilla – the Western Gorilla, Gorilla gorilla, and the Eastern Gorilla, Gorilla beringei. Gorillas live in dense forests in western and central tropical Africa. Gorillas are the largest of all primates. Their features include:

considerable sexual dimorphism in which the males are about twice as big as the females

bodies adapted for climbing trees (when young) and also for quadrupedal (four-legged) movement on the ground. These adaptations include arms and shoulders that enable them to swing from branch to branch (in lighter bodied, young gorillas); finger and toe bones that are long and curved for gripping tree branches and strongly built to support their large body weight; and knuckle walking’, in which they support themselves on the knuckles of their hands.

a diet of fruit, leaves and shoots

long, pointed canine teeth and long jaws

a social lifestyle in which about 10–20 individuals live in small, permanent groups

Chimpanzees

There are two living species of chimpanzee – the Common Chimpanzee, Pan troglodytes, and the Bonobo or Pygmy Chimpanzee, Pan paniscus. Chimpanzees live in woodland and forests in western and central tropical Africa. Chimpanzees are the smallest of the Great Apes and our closest living relatives. Their features include:

moderate sexual dimorphism in which males are slightly larger than females although this is reduced in Bonobos

bodies adapted for climbing trees and also for quadrupedal (four-legged) movement on the ground. These adaptations include:arms and shoulders that enable them to swing from branch to branch (especially in young, lighter bodied chimpanzees); long, curved finger and toe bones to powerfully grip tree branches; and ‘knuckle walking’, in which they support themselves on the knuckles of their hands.

a diet of fruit supplemented by meat

long, pointed canine teeth and long jaws

frequent use of tools, such as sticks, twigs and stones

complex social groups consisting of a dispersed community containing from 10 to 100 or more individuals that often divide into small foraging groups with a constantly changing membership of about 3–10 individuals

Humans

There is only one living species of human – Modern Humans, Homo sapiens. Humans now live in almost every part of the world.