Society values the biological nature of humans to perpetuate the species. Therefore, society upholds values that support the family, procreation, and the stability that results. Gender roles have evolved over time to a productive society. Humans have over populated the world and as a result mother nature steps in and creates non-reproducing humans (gender challenged, homosexual, etc.). Society naturally looks down upon those who do nothing to perpetuate the species, however the over population issue has be addressed as well, so these "others" keep the population to a manageable level.