Full Idea
Moral systems are defined relative to idealised family models (e.g. the Strict Father, and the Nurturant Parent models. What counts as 'altruistic' is very different in different family-based models.
Gist of Idea
Moral systems are based on various models of family life
Source
G Lakoff / M Johnson (Philosophy in the Flesh [1999], 25 'Evolution')
A Reaction
[See Ch 14 of this book] This doesn't offer an account of fundamental metaethics, but it is a good proposal for the sources of the various normative systems. How should strict fathers or nurturers acctually treat children. There are strict nurturers!
Book Reference
Lakoff,G/Johnson,M: 'Philosophy in the Flesh' [Basic Books 1999], p.559