I took a Bio anthro class once. I asked the professor the question "If being Bi-pedal was so advantageous to the early homos, why don't we have a larger diversity of bi-pedal species?" She replied, "That's a very good question! Get your PHD to find out."

I walked out of class, rolled my eyes, and mumbled to myself. "Yeah because you don't have a fucking clue, and neither does anyone else."