People who evolved for colder climates traditionally can eat lots of meat and dairy products. A high protein and fatty diet keeps their bodies warm in the winter. Digesting milk also offers a nutrient boost as well as a vitamin D boost. But most people who evolved for hotter climates can't even digest the lactose in milk. Their ancestors were fruitarians and vegans, such as Central Africans and East Asians. In conclusion, there is no such thing as a universal diet for all mankind.