Vegans also claim they enjoy perfect health when they exclude all animal protein from their diet. And it's true that for the most part they do see improvements when they switch over from the SAD diet. The honeymoon can last years... and then the nutritional deficiencies and long-term damage kicks in.

Human are opportunistic eaters. If there was edible plant matter to be eaten, it was eaten. If it was tasty and/or provided nutrition, it was eaten whenever available. And it turns out that this is the case even in places like the arctic. Why is anyone surprised.