Before agriculture there was horticulture and before that there was hunting/gathering - with gathering being the much more dependable.
Humans in the wild still gain the majority of their calories from carbohydrates. Meat and fish are a major source of necessary protein - but the vast majority of energy was still derived from carbohydrates.
Our molecules of metabolism are set up to burn carbohydrates as the primary energy source.
yeah, stuff to repair various body parts takes fat and protien molecules, actually amino acids and triglycerides, but for energy, actual energy to fuel the activity of the body, it is glucose.
carbs get converted to glucose, fats are three glucose molecules stuck to a fatty acid, and proteins get deaminated and rearranged molecularly into, yes, glucose, then they are thrown into the furnace.
Balanced diets are good because the provide all kinds of materials in various quantities that we need to maintain life and do ongoing repairs.
But energy, is derived in the end from glycolysis, which is fed by carbs directly, fats (the preferred stored arrangement, due to weight/cal ratio) and protien, which are converted to glucose, then fed into the glycolysis furnace.
“Humans in the wild still gain the majority of their calories from carbohydrates.”
This is true. We don’t have to speculate about paleolithic diets when there are people still living in the paleolithic era today, and for a lot of those people meat is a treat, not a staple. Also, they often need to supplement their diets with grubs because eating wild game doesn’t give them enough fat intake to be healthy.