> Is your argument then that societal policy should only be based upon real on-average differences?

I wasn't actually making an argument beyond what I posted; if I was to provide an explanation of its relevance it is that it is a fairly common position that real and relevant differences are a necessary, but not necessarily, sufficient condition for policy distinctions, and that insofar as the subthread on the advantages of being with the mother was relevant to the broader subject to start with, it remained relevant (though not, in and of itself, demanding any particular conclusion) as long as there was a real, on-average difference.