Differing degrees of assortativity in matching can be expected to have both genetic and cultural determinants. When assortativity is subject to evolution, the main result of Alger and Weibull (2013) on the evolution of stable other-regarding preferences does not hold. Instead, both non-Nash and Pareto inefficient behavior are evolutionarily unstable.
Published in the International Journal of Game Theory (2016). Link to paper.