Elaine Sunde wrote: > When the science says that two individuals shared a > common ancestor does the statement exclude the > possibility that one of the individuals descends from the > other? (I've always been confused on this: Bob and his > son Tom do share a common ancestor, that is Bob's father > is Tom's grandfather....) I may be the least informed of the individuals who tested, but my guess is that a shared common ancestor is *any* shared common ancestor. If anyone has better information, please set me (and us) straight. The baffling thing about the DNA testing we did is that Buzz, who descends directly from Capt. Thomas as I do, tested closer to Mo (who descends directly from Henry Brooks) than to me. The lab provides some fairly indecipherable advice about checking in such cases whether matching testees might share (other) common ancestors. I suspect, in my case, that's the issue, since I also descend (through a daughter line) from Henry. I posed this issue to the lab before purchasing the test, and they replied, no, you're not disqualified as a testee of Thomas's line. However, I am very much wondering right now whether my mixed lineage explains the surprising results. Basically, it has to do with mutations — the more generations Buzz and I have been isolated genetically, the more mutations (differences) we ought logically to have, as these only develop over time. At least I *think* that's right. I probably should shut up, as I need to figure these questions out. But we can say with certainty that Mo, Buzz and I all share a common male ancestor, and therefore that Thomas and Henry of Massachusetts Bay were closely related. If Henry and Thomas were first cousins, they would share a common Brooks grandfather. The test does not, cannot, identify the specific common ancestor. You just get a range of probabilities. "In comparing 37 markers, the probability that Clarence M. Brooks (Buzz) and Christopher H. Brooks shared a common ancestor within the last 4 generations [is] 4.15% 8 generations 28.17% 12 generations 59.4% " etc. Chris