How do we know if an early ape-man or woman walked upright? An examination of certain bones -- a tibia (leg bone) or a pelvis, for example -- can reveal the answer. So can fossilized footprints.

Some of his Continental critics regarded Pithecanthropus as a gigantic gibbon; others gave the thigh bone to an extinct form of man and the skull cap to an extinct form of ape. British anatomists ...