http://www.newscientist.com/article/...6_head_dn14564
According to this study, men from polygamous cultures live quite a bit longer than those from monogamous cultures, and the hypotheses for this longer life include:
They take better care of themselves as they still have children to support as they get older.
There is evolutionary selection for longer life, as the longer life means more genes passed on thru young, fertile wives.
And my personal favorite - they have multiple women to take care of them when they get decrepit.
Ah yes, that's what I need when I'm a geezer - a few wives to share out the unbelievable fun of emptying my bedpan and giving me sponge baths.