The recent chimpanzee attack has raised the issue of how strong chimpanzees really are — a question that lacks a solid answer, since chimps rarely compete in either Olympic-style weightlifting or powerlifting.
The Human Evolution Coloring Book provides a useful illustration of the Comparative Anatomy of Chimpanzees and Humans:
Notice that the chimp has roughly twice the relative arm mass of a human. That alone would imply that chimps are stronger but less than twice as strong as similarly sized humans — 22/3 as strong — but their arms aren’t simply bigger human arms. How close tendons attach to the joint, for instance, can dramatically affect the mechanical advantage of a muscle — whether it’s naturally in low gear or high gear, so to speak.
Our illustration has other limitations, too. First, it shows a gracile chimpanzee, the Bonobo or Pan paniscus, rather than its more robust cousin, the Common Chimpanzee or Pan troglodytes. Second, it shows a human female, which arguably exaggerates the difference in upper-body and lower-body mass between species. Adult human males have dramatically more upper-body mass than females.