The MacEgan, Egan, Eagan, Eagen,
Agin, Agins, and Keegan Families 

Generations to Most Recent Common Ancestor

The most commonly used measure of difference between your DNA and that of someone else is the number of markers (Alleles) which are different. This is a simple count and does not take into account what can actually happen. In practice more than one marker can change in a generation and some markers change more rapidly than others.

An Alternate Measure

It is possible to do a little mathematics to calculate how far back in time, in terms of the number of generations, two people may have a common ancestor. This is called the time to most recent common ancestor (TMRCA). To do this, we assume any number of markers, not just one, can change within one generation (Infinite Alleles), and we use the probability (mutation rate) that a specific marker will change.

In our case the mathematics to perform the analysis has been done and is incorporated in the Genetic Distance Calculator on the McGee Family Surname Site. The options we have chosen are Infinite Alleles and the mutation rates due to McDonald. If you are interested, you can read the paper by Bruce Walsh entitled Estimating the Time to the Most Recent Common Ancestor for the Y chromosome or Mitochondrial DNA for a Pair of Individuals.

What Does this Mean?

If you click on your FTDNA kit number in the Index below you will see your entry and (hopefully) one or more other kit numbers listed under it, each preceded by a number in { }. This number is the number of generations back that you both may share a common ancestor with a 50%, or flip of a coin, chance.

If you don't yet know where in Ireland you came from look at the ancestors of those who are less than {20} away first to see if that helps your search.

In practice {8} generations back is not all that far and someone with a {3} generation tag may have in fact identical markers and be as close as a sibling or child - this game is all about chance.

What to Do Next?

If you wish to email any participant, please draft a note saying a little about your family and your reason for exploring a potential or real family relationship (including your Kit Number and that of the person you wish to contact) and send it to us. We will then forward it to them with your contact details. This roundabout approach, as you will appreciate, is to preserve privacy if participants so desire.

VERY IMPORTANT: If you have recently had success in locating your oldest ancestors more precisely than say "Ireland" or have more accurate dates please let us know and also, if possible, update your FTDNA entry. We can do this for you if you wish or do not know how.

Index (37 markers)


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