I'm eminently qualified to respond, having no children of my own, having no background in science, no medical knowledge, nothing, nada, zilch. Therefore, except for one or two of the aforementioned, similar to the op in that regard,
My guess is seeing/living/experiencing the people (i.e. parent or parents, in most cases) who are responsible for nurturing, and then copying what they do, is what's going on. So, if while that tot is sucking on his/her formula at McDonald's, while mom is shoving a burger and fries down her throat, that tot is gonna want the burger/fries at some point. On the other hand, if mom is gently sharing her stir-fired greens with tot right from the minute that tot is able to eat real food, tot is not gonna be green averse.
I've seen some similar stuff in our travels; I love how moms/dads share from their plates, stuff that would've never crossed my parents' minds to share with their kids.
