Your question is misguided in two ways.
One, you assume that premodern diets are by definition optimal.
If we can know the macronutrient ratio of Fat:Protien:Carb of early humans and primitive tribes we get a glimpse of the best diet there is.
No, we can't. There's no reason for an indigenous people's diet to be optimal in any way. It simply does not logically follow. We know, for instance, that several indigenous peoples were forced into their current diet and way of life by being chased from other lands. They made the best of what they found in their current homeland. Why would that be optimal?
Secondly, there is no "best diet". For one, people vary. There seems to be evidence that some people and perhaps groups of people do better with some diets than others. Furthermore, the range of well-functioning diets for a given person likely has room for multiple contradictory diets. Someone might find themselves doing well with a low-carb paleo diet might also, under different circumstances, do well with some high-carb diet. Other life factors play a role there.
This comes into irrefutable focus when you notice that many premodern diets do not resemble each other. Many native peoples who live in the far north eat almost exclusively animal products and practically zero vegetables or carbs, whereas we see evidence of human reliance on roots and tubers in prehistoric Subsaharan sites. These extremely disparate diets cannot be reconciled in a single prescription.