Ancient DNA Methods Video 10: Why are f3s negative? The math of f-statistics

Admixed populations generate negative f3s, but why? Why are f2s always positive? And what is the math behind f2s, f3s, and f4s? All these questions and more are answered in the 10th video in my ancient DNA and population genetics series. The rest of the playlist can be found here:
https://www.youtube.com/playlist?list=PLPgiJTW5erxS8DXH5o9B-EViyMwZfaQDa

If you want to check your understanding, I recommend attempting to complete this homework assignment I wrote:
https://github.com/danieltabin/ADPGTPS/

Видео Ancient DNA Methods Video 10: Why are f3s negative? The math of f-statistics канала Daniel Tabin