[rxaxm]

> Topping the list for common genes were those related to our sense of smell. One explanation for this is that people with similar olfactory genes will smell things in the same way and so be drawn to (or repulsed by) similar environments... The opposite pattern held for genes related to immunity -- friends tended to be less similar at those parts of the genome.

This makes me think of the thesis of "Sex At Dawn" by Christopher Ryan and Cacilda Jetha. If humans evolved as polyamorous foragers for whom communal bonds were more important than paternal certainty, then it makes sense that you want your friends to like the same environments and add immunological diversity to your shared gene pool.