In the traditional model in poorer societies, you rely on the family or tribe. When you are in trouble, family helps.
Otherwise you help the family. It’s that contract or the modern one. The essence is the same. When needy (kid or senior) they provide for you, when productive, you provide for them.
So you look for partners that can in the long run raise kids, provide security and help needier family members. Traditionally, elders guide you or even make the partner choice for you, they counter your adolescent urges to hit off with a beautiful stranger of dubious future.
Family drama ensues if you run off with a stranger, someone who is not from the same village square (see the related blog post).
Western parents bitch and moan, some kick you out of the house, try to disinherit you, whatever little they can do.
In traditional societies, they can impose harder sanctions, even kill you (if you re a girl mostly).
The driving force behind the sanctions is always the fear that you leave the family, meaning you and your ‘stranger’ will no longer be part of the ‘contract’ to help the needier family members. Part of the sanctions is withdrawal of family support to you. Their investment in raising you to participate and contribute later is lost. Sure, they are pissed off.
Watch any soap opera in any culture (I suspect, since I have not seen too many) and you will find the stories revolving exactly about that.
What about love?
Maybe in some later blog entry :)
This post just tries to propose the economic basis under the subject of who to have a relationship with. The minefield of taboos and fears…later.