Thank for some very good responses. Good suggestions. As to: "People living in Europe know where they came from (may still be living in the ancestral regions), so feel no need to test." I have a little bit of a quibble with that. What people may believe is not necessarily so. There are some in the US whose families have been in the same county longer than many in Europe. When one looks at the history of Europe, one sees much population movement through the ages. Wars, famines, Plague, religious changes, the Industrial Revolution -- all caused people to move to different places. Europeans haven't been quite as "settled" as we might imagine. If they think they "know where they came from" they could easily be wrong. I look at European history and see a continental population in flux, from pre-history to the present. Let's take three examples, Huguenots, Palatines and the Plague: * Louis IV of France issued the Edict of Fontainebleau in 1685, expelling from 210,000 to (as he claimed) 900,000 Huguenot Protestants from France. Only a few of these came to the Americas; many went to other parts of Europe, especially including England. * The Palatinate (roughly today's Rheinland-Pfalz federal state of Germany) has been de-populated and re-populated many times. It suffered the curse of being in between warring armies practicing "scorched earth" policies. After each destruction, the fertile soil would attract new people from Switzerland, France and other areas. It wasn't until after the famine of 1708 that Palatines began arriving in America. * The Black Plague hit Europe (for the first time in several hundred years) in 1348 and struck several more times until the mid-1450s. Up to 40% of the population was suddenly gone. Panicked city-dwellers fled to the countryside; serfs whose masters had died started looking for work where someone could pay them; masters whose serfs had died were willing to hire strangers. A huge circulation of the population put families in places they'd never been before. (And, BTW, gave us surnames.) We tourists may look at a 12th century castle and think it was manned by ancestors of the same people living in the area now. Maybe, maybe not. >From the perspective of recruiting participants, though, the historical reality matters less than what they believe. A person who "knows" is less likely to learn than one who's curious. European DNA might reveal some surprising things to the participants. How to convey that? -ralpht_/)