I've said it once already but I'll repeat it again. Q misquoted me. I never said anything about bipedalism. birds went bipedal because of an adaptation to flight. Not so but an easy assumption to make. Birds are descended from small bipedal donosaurs. They evolved bipedalism to increase running speed. Clearly this is not the reason we developed it. We are the slowest of the great Apes. We are more than just bipedal. Birds have a forward stooping gait balanced by a tail. Except for the penguin ofcourse. It's back is straight and its head connected centrally atop the spinal collumn rather than slightly forward. Just like us. Would you argue that Penguins aren't semi-aquatic? What would happen to them if they were suddenly forced to live in savannah? They would likely seek out rivers and lakes if they survived(dubious). We went from a semi-aquatic existance to savannah but had hands with which to use tools. We had learned to use rocks on shells and spears on fish over a million years or so and took these skills with us. We took shelter where possible in rivers where big cats did not like to follow but this shelter was not always available. The weapons kept us alive on the open Savannah. We were forced to become more proficient with them or else face extinction from big cats. In time we went from defending to attacking. During dry spells there would have been insufficient food in rivers. So we went after other game.