Bipedalism is the ability to walk permanently upright on two feet – a characteristic that distinguished the early hominids from the apes. The question arises whether all intelligent, technological species in the Universe display this characteristic. According to one school of thought, large-brained, land-dwelling life-forms need a vertical posture in order to balance the weight of the head on top of the spinal column. Moreover, the transition to two legs frees the hands for delicate manipulation which is essential for tool-making. Contrasting with this is the view that any speculation based on anthropomorphism is likely to prove too restrictive when considering the forms that advanced organisms can take on other worlds.