It's okay that you like berries. So do I. But that doesn't mean it's the best source of the nutrients in them. Sugar is bad for us. Carbs are bad for us. You can moderate them and reduce the odds of complication, great. But that doesn't mean that early human diets are necessarily good, and not every group of humans would necessarily benefit. Cancers feed on excess sugar. That's their food. They don't really like fats and protein. This isn't a huge jump in logic. They are eating what we eat.