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Did the human hand evolve for boxing (too)?

That is the intriguing conclusion of a new study:
Michael H. Morgan and David R. Carrier, Protective buttressing of the human fist and the evolution of hominin hands. The Journal of Experimental Biology, 2012. Freely accessibleLINK [doi: 10.1242/​jeb.075713 ]


Summary

The derived proportions of the human hand may provide supportive
buttressing that protects the hand from injury when striking
with a fist. Flexion of digits 2–5 results in
buttressing of the pads of the distal phalanges against the central palm
and
the palmar pads of the proximal phalanges.
Additionally, adduction of the thenar eminence to abut the dorsal
surface of the
distal phalanges of digits 2 and 3 locks these
digits into a solid configuration that may allow a transfer of energy
through
the thenar eminence to the wrist. To test the
hypothesis of a performance advantage, we measured: (1) the forces and
rate
of change of acceleration (jerk) from maximum
effort strikes of subjects striking with a fist and an open hand; (2)
the static
stiffness of the second metacarpo-phalangeal (MCP)
joint in buttressed and unbuttressed fist postures; and (3) static force
transfer from digits 2 and 3 to digit 1 also in
buttressed and unbuttressed fist postures. We found that peak forces,
force
impulses and peak jerk did not differ between the
closed fist and open palm strikes. However, the structure of the human
fist
provides buttressing that increases the stiffness
of the second MCP joint by fourfold and, as a result of force transfer
through
the thenar eminence, more than doubles the ability
of the proximal phalanges to transmit ‘punching’ force. Thus, the
proportions
of the human hand provide a performance advantage
when striking with a fist. We propose that the derived proportions of
hominin
hands reflect, in part, sexual selection to improve
fighting performance. 
 

I wouldn’t dare to comment much but for what I have read in the paper, it looks plausible, notably because it is indeed significantly efficient versus the open hand (as much as 3x) and because chimpanzees can’t do it… but australopithecines could. 
However I can also imagine this development as a side-effect of other adaptive uses of the hand, such as grabbing a spear, which is no doubt a much more daunting weapon than a naked fist… in most cases at least.
Fig. 2
 
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Posted by on December 20, 2012 in biology, hand, human evolution