Originally Posted by Myst

A biped is an animal that travels across surfaces supported by two legs.

Bipedalism in general
Bipedal locomotion is walking, running, and standing on two legs (as opposed to four). It is a process requiring complex interaction of mechanical and control-system characteristics. Humans are capable of performing such motion because their spines are s-curved and their heels are round. Whether such a system has evolved in an animal species or been engineered in a robot, many of the same issues are inevitably involved.


If you want more proof of how humans came to be
http://en.wikipedia.org/wiki/Australopithecus_anamensis
look at the species list on the left, its all there.