Today, DNA ancestry testing is big business. Companies now claim to reveal our ancestral origins and ethnic mixture with pinpoint accuracy and at affordable prices. But how do these tests work? And is identity really all in the genes? In this public talk for the 2017 Pint of Science festival in Cambridge, Hannes Schroeder and Sarah Abel explore what genetics can tell us about who we are and where we come from, by taking a look at the science and social uses of DNA ancestry testing.