The Mongol Empire, the largest contiguous land empire ever known, was founded by Genghis Khan in the early 13th Century. From small beginnings in rural Mongolia and fighting with archers mounted on swift horses, the Mongols spread from Central Asia, first subduing China then spreading west to Baghdad and as far as the shores of the Mediterranean. In a survey of Central Asian men, scientists noticed the widespread occurrence of a Y-chromosome with a particular genetic pattern. Its geographical distribution coincided with the extent of the Mongol Empire and together with other evidence, led to the conclusion that this was the Y-chromosome of none other than Genghis Khan himself. His habit of slaughtering vanquished males and inseminating their womenfolk, which tradition he passed down to his sons, was responsible for the astonishing spread of his Y-chromosome across Asia and further afield. An estimated sixteen million men carry the Genghis Y-chromosome today. One of Oxford Ancestors customers, Tom Robinson, from Florida was one of them - much to his surprise.