DTC DNA tests complicate family trees

A recent article in the New York Times describes cases of individuals identifying surprising aspects of their ancestry through direct-to-consumer DNA tests (e.g. 23andme, ancestry.com). The article also summarizes a study comparing self-reported ancestry (via census) and DNA-based ancestry for 160,000 Americans. About 4% of those who checked "white" on the census had partial African ancestry, and this was highest in the southern states -- e.g. 13% in South Caroline. The article does an great job clarifying that ancestry and race are not the same thing.  Ancestry is a biological concept, race is a social one.