Why Do We Care About Our Ancestors?

This article is an edited excerpt from the new book "Ancestors & Relatives," from Oxford University Press.

Why do we consider Barack Obama a black man with a white mother rather than a white man with a black father? What are the implications of knowing, as we now do, that chimpanzees are genetically closer to humans than they are to gorillas? Why did the Nazis believe that unions between Germans and Jews would produce Jews rather than Germans? Are sixth cousins still family?

In order to even address, let alone answer, such questions, we must first examine our unmistakably social visions of genealogical relatedness. What we need, in other words, is a sociological understanding of ancestry and descent.

As evident from the wide popularity of the television series “Who Do You Think You Are?” and the dozens of websites (such as Ancestry.com, Family Tree DNA, and FamilySearch) and software programs designed to help people construct their family trees and discover hitherto unknown ancestors and relatives, we certainly have a tremendous fascination with genealogy. Every day thousands of “root...