You do realize that we have evolved right?? We eat whatever the fuck we're in the mood for whether its good or bad for our bodies (chips, ice cream, soda, fast food), people literally consume poison KNOWING its bad for them (cigs, drugs, very unhealthy food/drink.. you can argue those people are mentally ill, but not all of them are. sometimes people just do what they're in the mood for, and that mood is not always bodily preservation), people don't have sex all willy nilly in order to reproduce constantly, some people don't want kids at all, and on the topic of sex nearly everyone who can uses birth control because sex becomes about pleasure and intimacy instead of popping out kids. People date ugly, unfit people, and people marry disabled people, saying fuck you to nature's laws of attraction. Same sex couples, people marrying those who are sterile, people marrying bad people simply because they feel they love them... genetics and instinct are almost always underlying, but we are civilized people, not primates..