Hi Guy,

The above figures show why DNA testing is not really worth while for genealogy yet.

You have said this before, but it simply isn't true, for most people at any rate.

Yes, the number of people who have tested is small, but consider:

1. If we consider just 4th cousins or better, which is 5 generations to the common ancestor, each tester will have 63 ancestors (except in endogamous populations). If there are 10 million testers (assuming 5 million are doubled up), then there are potentially 630 million ancestors. Now of course many of those will be multiples also, which is exactly what we want, say half of them = 315m. Virtually everyone I am connected to is in USA (330 m), UK (67m), Canada (38 m) and Australia (25m), a total of 460m. So 630m or 315m ancestors is looking pretty reasonable.

2. If we consider any one of our pairs of ancestors, the ones 5 generations back could easily have several thousands of descendants today. If we make some assumptions, for the purpose of the exercise, of how many children each couple had and how many of them had children, it is possible to make a calculation for each pair. Assuming only 7, 6, 5, 4 and 3 children for the generations, we'd get roughly 2400 descendants for each 5th generation couple, 360 for 4th, 60 for each 3rd, 12 for each 2nd and 3 for our parents' generation. Multiply that by the number of couples in each generation and the total number of present day descendants of all our ancestors = 16 x 2400 + 8 x 360 + 4 x 60 + 2 x 12 + 1 x 3 = 41,500. If I have done the calculation correctly, that is a very approximate estimation of the total number of possible 4th cousin or better matches any of us have. If we included out to 8th cousins as Ancestry does (which I think is not generally very useful), then the number would be absolutely enormous. So there is no shortage of potential matches. Of course I don't pretend that these figure are any more than notional, but they are illustrative.

3. And so it is no surprise that I have several hundred (only a few are repeats) 4th cousin matches on Ancestry and FTDNA out of the possible 40 thousand, or whatever the figure is, and 17 thousand Ancestry matches overall.

4. But the real proof, which you seem to have not considered, is that people are finding relatives they couldn't find any other way - adoptees, people with uncertain parentage, people whose ancestors' paper records are lost, etc. If you check out adoptee websites, you'll find plenty of success stories - and a few disappointments too!

5. In my own situation, both my maternal grandparents were of unknown origin due to an adoption, possible false names, no record of father's name, etc. DNA has enabled me to solve one of the mysteries and I have high hopes of resolving the other one day.

So a rough estimate of numbers and the real experience of many people shows that DNA is a great boon to genealogy. It doesn't solve everything of course, and it generally requires a lot of work to be done, but for many of us it is absolutely essential.