8.3.4: The Apes

Superfamily Hominoidea

All apes live in Africa or southern Asia. Compared to monkeys, apes are larger-bodied, larger-brained, and most are adapted for spending time on the ground. One of the easiest ways to tell an ape from a monkey is by the absence of a tail.

Apes are divided into two main groups: the small-bodied apes — gibbons and siamangs — and the large-bodied apes — gorillas, chimpanzees, bonobos, and orangutans. Humans are also classified within this group, making us hominoids too.

Built for Swinging: The Ape Body Plan

What really sets apes apart from other primates is how their bodies are built for brachiation—swinging below branches using their arms. This form of locomotion has shaped some important features of ape anatomy. To maximize reach, ape arms are much longer than their legs. Their torsos are broader and more upright than those of monkeys, and their shoulders and arms in particular have a much wider range of motion and flexibility. The collarbone (clavicle) is longer than in other primates, which stabilizes the shoulder joint and allows apes to rotate their arms a full 360 degrees, making them the best adapted primates on the “monkey” bars.

Distinctive Molars

Another feature that sets apes apart is their Y-5 molar pattern. If you look at an ape molar, you’ll find five cusps arranged with a groove between them that forms a “Y” shape. This pattern was also present in the common ancestors of apes and Old World monkeys, making it a useful trait for tracing evolutionary history.

Slow to Grow, Slow to Reproduce

As hominoids, apes and humans share another distinction: we have the longest life histories of any primates. Apes take a long time to reach adulthood, and females reproduce far less frequently than monkeys do, often raising one offspring at a time over many years. This slow reproductive rate, combined with habitat loss, hunting pressure, and poaching, is a big part of why apes are among the most endangered animals on the planet. It also helps explain why, despite being around for millions of years, there are relatively few ape species compared to monkeys.

In the sections that follow, you'll be introduced to the six types of non-human apes that still share the planet with us. Only one hominoid is a serious threat to all the rest: us. As you get to know our closest living relatives in the pages ahead, it will become clear that their fate, like so much of the natural world, rests largely in human hands.