A group of researchers led by Martin Nowak, a professor of biology and mathematics and director of the Program for Evolutionary Dynamics at Harvard University, wrote in to tell us about their new paper, in this week's edition of Nature:

We show that individuals who engage in costly punishment in a cooperation game do not benefit from their behavior. The study found that the use of punitive behavior correlates strongly with reduced individual payoff, and bestows no benefit on the group as a whole.
These results demonstrate that costly punishment is not an effective force for promoting cooperation. The unfortunate tendency of humans to engage in acts of spiteful punishment must have evolved for other reasons such as establishing dominance hierarchy and defending ownership, but not to promote cooperation. In cooperation games, costly punishment is a detrimental and self-destructive behavior.
Our finding has a very positive message: In an extremely competitive setting, the winners are those who resist the temptation to escalate conflicts, while the losers punish and perish.
—Anna Dreber, department of economics, Stockholm School of Economics, Harvard's Program for Evolutionary Dynamics
David Rand, Harvard's Program for Evolutionary Dynamics and department of systems biology
Drew Fudenberg, Harvard's department of economics
Martin Nowak, Harvard's Program for Evolutionary Dynamics, department of mathematics, and department of organismic and evolutionary biology