Chimpanzees are about 1.35 times stronger than humans, according to a new study. But despite tales of superpower-like strength from chimps, this difference might be because humans are comparatively weak, not because our cousins are preternaturally strong.

Why it matters: The researchers think humans might be weaker than chimps because, as our ancestors became bipeds, our muscles were selected for chasing prey for long distances rather than quick feats of strength.

The authors found that human muscles are structurally different from chimpanzee muscles — and the muscles of most other primates. The chimpanzees studied had balanced amounts of slow-twitch and fast-twitch muscle fiber, which was consistent with past studies of primates. Humans, in contrast, contain have much more slow-twitch muscle, which is associated with endurance running, not strength.