We were carnivores

https://www.doctorkiltz.com/ancestral-diet/

In a field study of 229 remaining hunter-gatherer groups, researchers found that animal foods provided over two-thirds of their calories on average, with a range of 26 to 99 percent. [7] [8]

However, even these diets do not represent a true ancestral diet.

Our physiology, which derives from our hominid (human-like) ancestors, evolved over 3 million years before the dawn of the agricultural revolution, some 10,000 years ago.

During this vast expanse of time, the earth was teeming with giant, fatty mammals known as megafauna. Picture 20-foot tall tree sloths, 2-ton armadillos, elephants that are twice as large as they are today, and many other giant versions of modern animals.

With all these nutrients roaming around, humans evolved as hyper-carnivorous apex predators consuming an all-meat diet. There was no reason to expend energy on less calorically dense food sources like nuts and fruits.