Not sure what a traditional bushman is. Are you refering to the san bushmen who eat a lot of mongongo nuts? That is a strange exception, and those people are hunters who eat a lot of meat anyway.

There are abundant written accounts of native north americans. There were those who grew corn and squash, which means they have little in common with paleolithic humans who had no such crops. And there are those that did not grow crops and ate mostly game and fish.

Anywhere away from the equator there is virtually no gatherable plant food for most of the year. Before domesticated crops, people clearly ate mostly animals, fish, and insects.