It's been a long-held consensus that our hands evolved an opposable thumb and general shape to help us better grip things like tools. However, a new study by the University of Utah suggest that the reason our hands are in the shape they are is because we needed to beat the snot out of things.
The lead scientist for the study says that there are many other shapes and forms that our hands could have evolved if it was just about gripping things. Other primates, he points out, have fingers that are too long to fold under the thumb to make a fist. When other primates fight, they are more likely to wrestle or hold their opponent down.
He also tested how important fists are: they studied with what force that 10 athletes could hit a punching bag, with a fist, open palm, or a fist with the thumb out. A thumb-out fist generates half the force of a normal fist. The open palm generates the same force, but isn't as concentrated as a fist.
Skeptics say that the haven't quite proven the hypothesis, and that punching might not have been the driver of the shape of our hands. However, if that hypothesis is true, it could explain another mystery: men with higher levels of testosterone have ring fingers longer than their index fingers, which seems to generate a better fist. This means that dominant males would tend to be better fighters.