This does not at all explain human behaviour: Most people would not shovel all the snow themselves while their counterpart chills in their car. And many people cooperate in prisoner's dilemma situations.

What explains human behaviour is that with every action we program ourselves to follow certain strategies and rules and that others can judge to some extent which strategies we programmed ourselves to follow. Thus we have an incentive to follow strategies that lead others to trust us, so that we'll have more opportunities for cooperation in the future.