> Racial identity is a social, legal, and political construct that consists of our own perceptions of our race, and how other people see us.

This seems a pretty US-centric conception. I for one wouldn't know how to assign a "racial identity" to myself, and most of my acquitances would surely say the same thing. I doubt that this study holds much meaning outside the USA.

Now if it was about genetic ancestry it would make some sense (and not really be surprising). But if it is about "self-reported identity" I guess it's only finding the correlation of that with actual genetically transmitted features.