A bit of spit and we can tell where our ancestors were at any given time in the last 200,000 years, according to Eddie Izzard. I watched enthralled, as he retraced the steps of his and our, ancestors from a group of 10,000 Homo sapiens living in ancient Africa, all the way to the 7 billion people populating the planet today. Thanks to the BBC, we were all able to see how far he and we have actually come. All it took was a bit of spit. I haven’t spat at anyone lately but I have been moved to wonder if our DNA recognises the places where our ancestors lived…