[Ibby]

Ha! I picked a nice time to chime in.
I honestly can't get my mind around the way this would possibly evolve. Maybe I've just been reading too much Dawkins lately (he's going to be on Up with Chris Hayes next week!) but, after all he has to say about investment cost - that is to say, a female has to invest exponentially more resources into creating offspring, regardless of whether or not there is mothering involved, than a male - I can't really wrap my brain around why or how it would evolve. In fact I suspect it's quite possible that it did, at some point, emerge as a mutation, which was then soundly selected against. Only in monogamous animals where both parents raise the offspring would it possibly be an evolutionary advantage. Any male in a species where males currently don't assist in raising offspring, would be at an evolutionary disadvantage if it produced milk, not to mention that as Clod pointed out, there's no practical chemical mechanism for males to know there's a baby of their own about. It would only make sense in us social animals, and even then, I'm not sure what would be different about society except that, yeah, I wouldn't have to keep checking to make sure my breast forms don't keep peeking out of my shirt.

So I guess my take on the question is, it's kind of like asking, what if every human baby born from today onwards was born with fully functioning wings. It's a hypothetical that just could not reasonably happen, so any idea as to the effects would have to be pure conjecture AND would have absolutely no application to anything resembling reality.

I'm not knocking you for bringing it up, mind you! i'm just saying, like, the question itself gets sort of rejected by my brain as such an impossibility that it just doesnt matter.