'Because the experiments show the proportions of the human hand provide a performance advantage when striking with a fist, we suggest that the proportions of our hands resulted, in part, from selection to improve fighting performance.
http://www.dailymail.co.uk/sciencetech/ ... erity.html
It also has some nice data on striking power.
The first experiment tested the hypothesis that humans can hit harder with a fist.
The researchers had 10 men - aged 22 to 50 and all of them with boxing or martial arts experience - hit a punching bag as hard as they could.
Each subject delivered 18 blows, or three of each for six kinds of hits: overhead hammer fists and slaps, side punches and slaps, and forward punches and palm shoves.
The bag was instrumented to allow calculation of the force of the punches and slaps.
To the researchers' surprise, the peak force was the same, whether the bag was punched with a fist or slapped with an open hand.
However, a fist delivers the same force with one-third of the surface area as the palm and fingers, and 60 per cent of the surface area of the palm alone.
So the peak stress delivered to the punching bag - the force per area - was 1.7 to three times greater with a fist strike compared with a slap.