What’s the number one food humans should eat?

There isnt any one thing for humans. Some species have evolved to live on a very singular kind of diet as you mention, but humans need a variety in their diet. We should have a lot more vegetable matter with some animal protein in modest amounts. Just look at our teeth and compare it to other species. A predatory cat has teeth made for killing and ripping chunks of flesh. Their stomach is much more highly acidic to digest raw meat. A horse has front teeth for cutting but large flat back teeth for grinding. Look at a humans…we have a little bit of both…..that says, from an evolutionary point of view, we need a variety on our diet