Ah TO - the old questions. How do you know that pandas eat bamboo? Because we have seen them doing this in the wild. I don't know if any zoo has ever tried to raise a panda on anything except for bamboo. If you put dogs and cats for generations in the wild, they will gravitate primarily to certain foods. Dogs in the wild mostly kill other animals to eat. Yes, both dogs and cats can survive on modern pet foods and live for a long time that include many things besides flesh foods. Dogs that eat lots of grains often end up with enlarged hearts and stones. I healed a rescue dog up from this with a raw meat diet.
Take any a dog (who has experienced raw meat) and put a piece of raw liver on one paper plate and a piece of fruit on the other plate and let the dog choose, the liver would be gone, probably along with the paper plate it was on, before the fruit was touched and the fruit might never get touched at all unless the dog was starving.... and yet.... some rare dogs will go for the fruit first.
With humans it is very different. Society, supermarkets, complex emotional and intellectual processes around food. The best that can be done is to put those two plates in front of you and try to let go the best you can and try to feel which raw platter your body wants. If you can't do that, and you are too socialized and un-in-touch, then you have to figure it out the same way you would if you were logically trying to figure out what the natural diet of a dog is. See if you can find any humans in the wild to observe. The best thing in my opinion, is to be able to get in touch with the place inside of yourself that just knows which plate it wants - like the dog. For humans it is more complex, because we have thoughts about the food on how it will make us feel not only physically, but emotionally and spiritually as well. Put raw meat one of the plates you are choosing from and some people (always - having experienced it first so they know it food and how it makes them feel) will not want the meat and others will feel drawn to it. But if you can't sense which one your body needs without all your social conditioning - then there are dudes like Weston A. Price etc. to help you to try to figure it out. Sometimes we just have to get cleared out of our old patterns long enough.
Of course - the key point is that it would have to be raw. No other animal cooks. Cooking changes the whole thing. It's just too hard to figure out what you would be grabbing and eating generally in the wild when you bring cooking into the equation. I'm not judging cooking in any way - just putting forth - that if you want a baseline of what basic food groups your species and your own body is drawn the most to - cooking will gum up the experiment.