In terms of absolute time, humans start walking later than most animals, but the delay has nothing to do with the fact that we walk on two versus four legs. With the exception of highly vulnerable quadrupeds like zebras, which risk being eaten by hyenas and lions and can walk within a day of birth, the age at which most animals start walking is primarily determined by how far along the brain has finished developing. Primates like macaques with smaller brains start walking at two months, bigger-brained chimpanzee infants require about six months to start walking, and humans start walking just
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