Social institutions emerge on the basis of the human cognitive ability to integrate an evaluation of the behavior and performances of other group members over long time periods.

The results of those evaluations are condensed into the social status of an individual, and that status is the link between short time achievements and long term success within the group.

Altruistic behavior on a short time scale can be advantageous for an individual on a longer time scale as it contributes to her or his status.

Conversely, building mating decisions not on events that may be quite random on a short time scale, but on long term accumulations is an evolutionarily rational behavior because it reduces stochastic fluctuations by averaging.