Carrying babies that could no longer use their feet to cling to their parents in the way that young apes can has long been thought to be at least one explanation as to why humans became bipedal. But University of Manchester researchers investigating the energy involved in carrying a child say the physical expense to the mother does not support the idea that walking upright was an evolutionary response to child transportation
http://www.sciencedaily.com/releases/20 ... 093254.htm