Genetic genealogy

Introduction

Traditional genealogy relies on documents - like census returns, church records, wills and BMD certificates. The problem with these is that they tend to become thin on the ground the further you go back in time. Records get destroyed or lost or perhaps they were never made in the first place. Even the records that you do have may not be entirely clear or accurate. They could even be ambiguous in so far as crucial identifying information is omitted. So how does one go about answering the questions like:

  • Do all Palins share a common ancestor ?
  • Are Palens in Canada related to Palins in England ?
  • Is Paling a variation of Palin or vice-versa ?
  • Where do the Ulster Pelans come from?

You can certainly gather together all the records you can find and attempt to build up a case by painstakingly examining them all. It is unlikely in the extreme that you will find definite evidence for all the potential connections. You may, as I have done, amass much circumstantial evidence but you are probably not going to be able to obtain records that go back sufficiently far in time or cover all the geographical regions involved. Remember that modern patrilineal surnames are potentially one thousand years old and most people are lucky to have complete records that go back 200 years.

Genetics

Genetic testing offers a solution. This is because modern surnames and the Y-chromosome share a common property - they are patrilineal - i.e. they are passed from father to son. A man will have the same Y-chromosome as his father, his father's father, his paternal great-grandfather etc. plus or minus a few statistical differerences that may occur at each generation.

What this means is that all males are effectively tagged with a genetic label which is closely linked with their surname. Thus men sharing a common patrilineal heritage will have a shared set of genetic markers in the same way that their surname is also shared. They can change the spelling of their surnames or indeed change them altogether but the genetics will still be true. In principle, if you have enough data, you can test a random male and tell what his surname is!

Genetic genealogy is now a growing practice that has been enabled by a number of commercial companies offering their testing services at prices affordable to many people. There are now many thousands of genetic genealogy projects each dedicated to particular surnames or regions.

Y-Chromosome Markers

So what are these Y-chromosome markers ? They are known as short tandem repeats - STRs. These are repeating sequences which occur at particular sections of DNA. The number of repeats at each marker can change by mutation - so you would expect that people with similar number of repeat counts for each marker are more closely related than people with bigger differences. People with the same surname and sharing a common heritage will have similar marker values - the closer the set of results are to each other the closer they are related.

There are a vast range of markers to examine, but you normally test specific ones that have been found to be useful. The choice is then down to the number of markers you test for - usually starting at 12, 25, 37 and 67. A test of only 12 markers does not typically provide enough information and I would recommend that 37 are tested for as a minimum. However, 12 is better than nothing.

The set of markers is called a haplotype and it is just a sequence of numbers. The closer the haplotypes are the more likely you are to be related. Bear in mind that genetics offers statistical certainty rather than absolute proof but this can normally be reduced to within reasonable doubt.

Problems with Non-Paternal Events

A number of challenges are posed of course. Some men will be adopted or otherwise will have taken on the surname of men that are not their biological fathers - so called non-paternal events (NPE). This presents us with a problem in so far as if we test a descendant of an adoptee their genetic markers will not be representative of their surname.  

Another short-coming of genetic genealogy based on the Y-chromsome is that it cannot say anything about lineages that have died-out or "daughtered-out" - i.e. if there were no male heirs at some point. As there is no male descendant left to test, genetic genealogy cannot access them. It could also be that an NPE lineage has survived whereas the original has died out.

What is the testing procedure ?

In practice, swabs are taken from the mouth of a candidate. The swabs are sealed in little vials and these are posted off to the laboratory for testing. After a few weeks, the results are made available by e-mail or via a web interface or they may be posted out to you. They will just be a set of numbers which will require interpretation and analysis by comparison with others found in various databases.

This is a skilled process but it is easy to learn. You can usually leave it to a surname project co-ordinator who will do the hard-work for you. Not only can it discover connections between families but it will also hint as to geographic origins (based on where mutual ancestors are known to have lived).

This is only a brief and non-technical introduction. If you are interested please have a look at the following links for more details and then e-mail me - dna 'at' pelan.org - or just sign-up at the main P-L-N Surname project site.