Actually (and I’m guessing), it would be the iron they’re after. I think … Yeah, I’ll bow to the weight of opinion but in my experience, yep. It would also seem to make sense; *something , presumably, needs replacing …
I don’t know how prevalent it is among other women, but I experience a pretty serious craving for red meat right before I start menstruating. Now I don’t know if my craving has anything to do with alleviating iron loss during my period, but I can tell you nothing tastes better than a rare steak right about at that time of the month.
I was once told that the desire to eat salty snacks like nuts and crisps when down the battle cruiser is a reaction to the loss of potassium.
I was, however, leathered, and so have no idea who told me or how reliable they seemed to be.
My sister craved snow cone ice all throughout her pregnancy. She didn’t want any flavoring added, just the ice. What is up with that?
Those are interesting studies, but they don’t really explain whether it is learned behaviour on the part of the chimps (like us going to the medicine cabinet when we feel ill or going on a diet when we find we’re too fat), or is a genuinely instinctive drive to fulfil a physiological need. The OP seems to be asking about the latter instinctive explanation only, since the case of learned behaviour obviously happens in humans.