It's in your genes: That's often how we explain away physical and personality characteristics. Genes hold a lot more information, however, than why you get freckles or can swing a baseball bat better than anyone else on the team. Using new scientific discoveries, genes may enable you to trace your family tree back not merely a few generations but hundreds, even thousands of years.

That's how Bryan Sykes, a human genetics professor at Oxford University in England, recently traced his lineage back more than 600 years. Using the Y-chromosome of his DNA and that of 250 other men with the surname Sykes, he discovered that almost all share one founding male — the original Mr. Sykes, who lived sometime in the 14th century, when surnames first came into use in England.