Here’s an accessible online post on how genetics (DNA) and ethnic groups relate. Using colours as an analogy, the post and the video do an excellent job in explaining why ethnic differences are socially constructed.
For further explanation around the video, check out the original post: https://www.open.edu/openlearn/science-maths-technology/can-we-be-categorised-our-dna by Kaustubh Adhikari where you can learn how scientist refuse to refer to human “races” despite seemingly conspicuous difference!
Didier Ruedin 