Why are chimpanzees so much stronger than humans despite being so much smaller?
Part of it is that the muscles are attached somewhat differently to provide greater leverage at the expense of range of movement. Another part is that the muscle fibers themselves are longer, so they can make larger contractions with greater force, again at the expense of small, precise movements. They likely have more fast-twitch muscle as well, allowing greater short-term exertions at the expense of long-term output. So basically, chimps evolved to emphasize strength for climbing ability and short term exertions such as fighting. Humans evolved to emphasize dexterity (for tool use) and longer-term exertions such as walking and running over the savannah.
