I am not quite sure of the evolutionary advantage provided by the behavior, but from the fact that so many toddlers fling their food, there must be something I am missing. Pretty quickly after making the transition from "baby food" to "real food", essentially from pureed pastes to stuff that needs chewing, Sidney also made the transition from "being fed" to "eating some, throwing the rest". To be fair, he also does a good share of "grab and put in mouth" (sometimes his mouth, sometimes Mommy's, sometimes inanimate objects ... you get the picture), but not a meal goes by without something going flying. Things get really interesting when he gets a hold of a spoon (wet-food catapult), fork (meat flinger) or spork (the perfect storm). He does not even need to be feeding himself, mind you, as he is more than happy to grab the utensil full of food out of your hand and fling whatever is on it. When he is feeling particularly creative, he will grab the utensil, wait for you to start pulling back and then just let go. That's right, he gets you to effectively throw the food for him. To punctuate the exchange, he'll usually laugh at this point.
But, I digress. For the most part, Sidney uses the Food Fling(tm) to indicate he is done with the meal, and this despite Mommy's (and the rest of the supporting cast's) constant reminders to the wee lad that "we do not throw our food." When we are home or visiting Abuela and Abuelo, this leads to a lot of vacuuming, clean-up and occasional "yeah, this is still good" munch by Dad (don't judge me, some of this stuff is tasty ... you have no idea what you are missing). However, when we are visiting Nana and the Admiral, it means that the puppies get snacks. So this leads to two Havanese being front and center for every Sidney meal, waiting patiently by the high chair. Sidney throws a piece of chicken nugget, mad dash by the dogs to get it. Sidney throws a piece of waffle, mad dash by the dogs. Sidney throws a piece of cracker, mad dash. You get the picture.
The downside is that having the dogs respond so positively to him throwing the food is that it "encourages" the behavior, despite the parental (and grand-parental) admonitions against his Tater Tosses. Actually, now that I think about it, kids throwing food at family animals would seriously ingratiate the tots to the pets ... leading to an extra set of eyes on the wandering infants. A rather elegant solution to the evolutionary question; a symbiotic development. Then again, the kid throws everything he gets his hands on eventually, so odds are the dogs just benefit. Also, 9 times out of 10 a Havanese will beat you to a flung chicken nugget ... in case you were curious.