Running on Two or on Four Legs: Which Consumes More Energy?

TLDR

There is disagreement about whether bipedal locomotion evolved as an economical means for long‑distance travel and about the energetic cost of freeing the hands. The study investigates the relative energetic cost of bipedal versus quadrupedal running in primates. Chimpanzees and capuchin monkeys were trained to run on a treadmill on two or four legs while their oxygen consumption was measured. Both species expend the same amount of energy running on two or four legs, indicating that the relative energy cost should not be used to argue for the evolution of bipedalism in humans.

Abstract

Disagreement exists over whether man's bipedal form of locomotion evolved as an economical means for covering long distances. There is also some disagreement about the energetic price man had to pay to free his hands. In an investigation of the relative energetic cost of bipedal and quadrupedal locomotion in primates, chimpanzees (Pan troglodytes) and capuchin monkeys (Cebus capucinus) were trained to run on a treadmill either on two or on four legs while their oxygen consumption was being measured. Both primates expend the same amount of energy whether running on two or on four legs. The relative energy cost of bipedal versus quadrupedal running should not be used in arguments about the evolution of bipedal locomotion in man.