why bipedalism 1

1) Which of the hypotheses explaining bipedalism discussed in the book or the NOVA interactive seem most plausible to you, and why?

2) Is it possible to test any of the hypotheses on the evolution of bipedalism? What types of evidence (fossil record, reconstruction of ancient environments, tool use, etc) would be useful in evaluating the various hypotheses?

3) What disadvantages or negative side effects are there to bipedal walking? Do we suffer any health effects that can be attributed to the stresses of walking upright?