Yup, Demon, I suspect you're correct. It probably goes back to Day One. We can't undo those "sins" either just by trying to eat like people did 10,000 or 100,000 years ago.
Over the past 500+ generations, our digestive systems have adapted to a diet of mostly cooked food and an omnivorous diet. All raw or all-vegan or paleo-style, meat-centered, lo-carb diets - these are all temporary curative diets. If we are sick it doesn't mean we need to reject what we've adapted to; it means we are probably full of toxicity from 100 different things and need a good cleanout.