Hugh Pickens writes "In 1935, JBS Haldane, one of the founders of modern genetics, studied a group of men with the blood disease hemophilia and speculated that there would be about 150 new mutations in each human being. Now BBC reports that scientists have used next generation sequencing technology to produce a far more direct and reliable estimate of the number of mutations by looking at thousands of genes belonging to two Chinese men who are distantly related, having shared a common ancestor who was born in 1805. To establish the rate of mutation, the team examined an area of the Y chromosome which is unique because, apart from rare mutations, the Y chromosome is passed unchanged from father to son so mutations accumulate slowly over the generations. Despite many generations of separation, researchers found only 12 differences among all the DNA letters examined. The two Y chromosomes were still identical at 10,149,073 of the 10,149,085 letters examined."