Why do humans stand upright? It's not for the reason many people believe

There are a number of theories as to why our ancestors evolved to walk on two legs. Some of them are patently ludicrous (see: aquatic ape hypothesis), but among the more sensible, the idea that we did it for cooling purposes is beautiful in its simplicity. This theory claims that we evolved to stand upright, in order… » 12/15/11 9:43am 12/15/11 9:43am