“In the penultimate stages of writing this book, the date of the great exodus from Africa may have shifted more than 10,000 years earlier than previously thought, following the discovery of forty-seven modern teeth in China. Then in the final stages it moved back by another 20,000 years with the detection of Homo sapiens DNA in a millennia-dead Neanderthal girl. These numbers are not much in evolutionary terms, ripples in geological time. But that is much more than the whole of written human history, and so the land continually and dramatically moves under our feet.”