Some norms are generic indeed like breastfeeding, some are not like "being seen as scum". Do not undervalue the power of cultural norms, they shape us social apes as importantly as genes. Indeed, it's been said (by paleontologists and ethnologists alike) that for humans (a social ape with complex language) cultural evolution have been more influencial than generic evolution. So bad we learn so much about genetics at school and comparatively so little about sociology and/or primatology.