I'm curious if this genetic diversity is just something that shows up as a number on a computer, or does it translate into something phenotypically* visible? A

I'm curious if this genetic diversity is just something that shows up as a number on a computer, or does it translate into something phenotypically* visible? Also, how much of, say, our medical/biological knowledge actually only applies to the descendants of the bottleneck mentioned in the post? I understand the "very diverse" in the article have better things to do than be subjected to researchers, but reading the article I can't help but be curious what this genetic diversity means in practice? *) not necessarily visually