Actually, you tend to crave foods you are allergic to - ie, processed or toxin-laden foods.  If your diet is made up primarily of whole, unprocessed foods and grown foods in their natural state, you will rarely - if ever - suffer food cravings.  Sugar and processed wheat products are foods most often craved.

Children crave protein and energy and dislike vegetables. Diet over the lifespan would be an interesting angle. My diet has definitely changed over the years.

Wasn't there a study done recently which suggested when people who are deficient in something, they find that foods containing a high amount of whatever they are deficient in taste sweeter?

So for example someone who is deficient in vitamin B will find bananas sweeter than they usually do.

Not exactly the same but it does suggest that our bodies remember these things and triggers subconscious reactons...

I had to go on a strict elimination diet for allergy reasons. A month into my new way of eating, I found myself having incredible cravings for pickles. I would eat up to three jars of pickles a week. Knowing that this was not normal, I discussed it with my doctor. Her suspicion was that since I was no longer eating much (if any) processed food, I wasn't getting enough daily sodium. I made a concerted effort to add salt to all of my cooking, and my pickle craving disappeared. I definitely believe that the body craves what it needs!