Just a few months ago my sister mentioned to me that her husband's U.S. ancestors all descended from just one married couple, who came to the U.S. around 1650, before having any children. She asked me how many living descendants (whether or not still in the U.S.) that family has today . I had nothing else to go on, so it was a rough seat-of-the-pants blue-sky back-of-the-envelope ballpark guesstimate. Just for fun I'd like to ask anyone interested in coming up with their own estimate to send it to me without posting it to math-fun. On Monday or so I'll post everyone's estimate (including mine). --Dan