Group selectionism alert. The "we are optimized for effectively playing the iterated prisoner's dilemma" argument, AKA "people will remember you being a jackass", sounds much more plausible.
I made no argument that cooperation emerges in the PD environment, quite the opposite. I argued that, once it emerged in a non-PD environment, it does not necessarily die out in a PD environment. No group selection required.
Hannes Rusch argues that the Prisoner's Dilemma is best understood as merely one game of very many:
http://www2.units.it/etica/2013_2/RUSCH.pdf