I was going to bring this up as an example. Listened to a book about the Comanches, and a lot of them basically ate meat. That’s it, for some of them. You go from that to high carb, and I can’t see that being good.
Listened to a podcast with a guy from the Sami people, who live far north and eat mainly reindeer. They do eat some fruits and the like in the summer. His grandfather die when he was around 90+ and had just cross-country skied to visit his friends. Yet his parents, who where taught to eat higher carb and not eat as much meat, died much earlier. He was trying to go back to his people’s original diet.
Now, how long does it take for a group of people to adapt to a diet? I don’t know. Can people of Asian heritage really eat rice and not want to eat bowls and bowls of it (as I do)? Maybe. If so, how long did it take them to get that way? Hundreds of years? Thousands of years?

They are just sour here, no sweetness whatsoever