If you want to let your imagination run riot, how about sensors in your fingertips which allow you to analyse the DNA of every individual you shake hands with (in the mode of Terminator 3), and the ability to link the data to a worldwide DNA database of all human beings alive (plus any remains of all the dead ones). On second thoughts, it may cross the bounds of taste and decency, plus the privacy lobby may get a little upset.

Joking aside, it would be amazing if that series of numbers gleaned from your inner cheek cells could tell you precisely when and where each and every one of your ancestors lived. But then again, it would take away all the fun of guesswork and speculation – and the internet woud be bereft of articles about Hitler’s Jewish ancestry, and Chinese villagers descended from lost Roman soldiers!