Originally Posted by Northcott
Damn me for a geek...
Several primates, apes (chimps, gorillas, orangutangs, iirc) among them, have vastly improved tensile strength in muscle fibres when compared to humans. Getting an estimate on how much more efficient is difficult, since defining a baseline "average" is near impossible, but estimates range from 6x to 12x. So while a baby chimp may not be stronger than an adult human, that 100 lb adult chimp is probably at least twice as strong as a very accomplished adult male weightlifter.
A full-grown silverback (male gorilla) can rip your arms off and beat you with the wet ends without working up a sweat.