As a recent reader of Reich's book "Who We Are and How We Got Here" I concur that he explicitly and forcefully refutes the notion of racial or ethnic categories as having any meaning over the lifetime of our species. Simply put, humans have migrated a lot and interbred with whoever. Your ancestry is a "tangled tree" (to borrow Quammen's term https://www.amazon.com/Tangled-Tree-Radical-History-Life/dp/...)