A recent paper (Morgan & Carrier, 2012)
suggested that there has been strong selection on human hands to be used as
weapons. This paper used an interesting method of investigation to examine
possible adaptations to striking in the human fist and made strong claims about
the split of the human hand from the rest of the hominid lineage. However, this
paper has overlooked some crucial points—which actually might serve to make
their case regarding sexual selection somewhat stronger than they appear to
have realised.
Firstly, the human hand is far from being
an effective strike tool—those of chimps and gorillas are far more effective
transmitters of force—as one might expect from an appendage that can also
support the animal’s entire weight. Secondly, there are trade-offs in any
adaptation. Specifically, the human hand shows a trade-off between holding and
hitting, with evidence much more in favour of adaptations to holding at the
expense of hitting. This might appear to undermine their case but only if one
assumes a history of the use of the fist in out-group conflict—something which
is unlikely for a variety of reasons. This is because—the final point-- while
there is some evidence of adaptation for the hand as a weapon, specifically the
mild sexual dimporphism in knuckle size, the authors do not go far enough in
distinguishing the likely contexts of this.
Human fists are actually highly specialised
weapons—of use only in ritualised in-group competition and only after much
training. Use of an untrained fist results in more damage to the striker than
the strikee. The context of sexual
selection on fists has likely included a lot more culturally-based
interactions. This latter realisation leads to some interesting empirical
predictions that could be tested across cultures.