Brachiation

Brachiation (from "brachium", Latin for "arm"), or arm swinging, is a form of arboreal locomotion in which primates swing from tree limb to tree limb using only their arms. During brachiation, the body is alternately supported under each forelimb. This form of locomotion is the primary means of locomotion for the small gibbons and siamangs of southeast Asia. Some New World monkeys such as spider monkeys and muriquis are semibrachiators and move through the trees with a combination of leaping and brachiation. Some New World species also practice suspensory behaviors by using their prehensile tail, which acts as a fifth grasping hand.

Some traits that allow primates to brachiate include a short stable lumbar spine, short fingernails (instead of claws), long curved fingers, reduced thumbs, long forelimbs, and freely rotating wrists.Modern humans retain many physical characteristics that suggest a brachiator ancestor, including flexible shoulder joints and fingers well-suited for grasping. In lesser apes, these characteristics were adaptations for brachiation. Although great apes do not normally brachiate (with the exception of orangutans), our human anatomy suggests that brachiation may be an exaptation to bipedalism, and healthy modern humans are still capable of brachiating. Some children's parks include monkey bars which children play on by brachiating.