I agree - I struggle with this too. I'm not convinced that in 500 years, European DNA has made it into every. single. individual. in South America. Similarly, I

I agree - I struggle with this too. I'm not convinced that in 500 years, European DNA has made it into every. single. individual. in South America. Similarly, I struggle to accept that the same is true for some of the indigenous people of Australia, or other similarly remote tribes. As a mathematical model, I don't doubt the assertion that it's possible one bit. But humans don't interbreed like that.