Sir- My family is participating in the Y-Line testing coordinated by George W. Page. I have some questions that maybe you could answer for me in laymens terms: 1. If two men of the same surname have identical Y-chromosome genetic data, it means they have a common paternal ancestor, right? But how recently? A common ancestor within the last 500 years? 1000 years? 10,000 Years? How far back do you have to go for the Y-chromosome genetic data of two men with a common paternal ancestor to be different. Will the Y-chromosome genetic data for two men with a common paternal ancestor 10,000 years ago look the same as if they were first cousins? If so, what good is y-line testing except to identify lines broken by adoptions? 2. If the genetic data changes a known amount for every so many generations, then you could tell roughly how closely two people were related. For Y-line testing, what is this accuracy? Plus or minus how many generations? Thanks very much for your help. Dick Hamly