(Where “supposed to” means “able to, leading to evolutionary advantage, with the result that the quality in question becomes attractive to potential mates”. I don’t know whether this just-so story is actually right, but it seems very plausible.)
[EDITED to add: “promote the interests of” is intended to cover providing food and shelter and other useful resources, protection against attack, persuading others to treat the family well, etc.]
Promote the interests of your family.
(Where “supposed to” means “able to, leading to evolutionary advantage, with the result that the quality in question becomes attractive to potential mates”. I don’t know whether this just-so story is actually right, but it seems very plausible.)
[EDITED to add: “promote the interests of” is intended to cover providing food and shelter and other useful resources, protection against attack, persuading others to treat the family well, etc.]