When people find out I have ancestors going back 13 generations in New Jersey, they think I must be largely Dutch or British – but that’s not the case. I know about these ancestors because they left a record, and that record survives. That isn’t the case for most of my ancestors. Genes and genealogy rarely align.

Let’s start with the genes

I’ve taken 4 DNA tests over the years and I’ve re-tested as the technology has improved. As the testing pool increases, so does our understanding where and how DNA can be geographically attributed – but even my recent tests differ in their geographic attribution. 23andMe says I’m 90% Scottish/Irish and Ancestry says I’m 97% Scottish/Irish – but that doesn’t really tell you the whole story.

For example, my maternal grandmother’s parents both come from Lancashire in England – so why isn’t 25% of my DNA English? Because people in Lancashire are on average 27% Scottish/Irish, 37% Anglo-Saxon and 17% French/German. In my case, the percentage is higher. Two of my grandmother’s grandparents came from Scotland and Ireland. So my grandmother – an American born English rose – was more than half Celt.

Adding to the confusion, when Ancestry.com assigns DNA as geographically “Irish”, they’re really mostly talking about the western coastal counties from Cork to Donegal. “Scottish” attribution, covers a geographic area that includes Scotland AND the Northern Irish Counties of Antrim and Down.

These 2 areas sit a few miles across the sea from one another and have deep historical ties. They were once part of unified kingdom called Dál Riata in the 6th and 7th centuries. That and Scottish migrations in the 12th, 16th and 17th centuries has made distinguishing these populations genetically complex. But from documentary evidence, I can tell you that the majority of my “Scottish” DNA probably comes from my paternal grandfather’s people in Antrim.

The remaining bits can be attributed as Anglo-Saxon, French, German, Dutch, Danish, with a 0.5% sprinkling of Finnish. There is also an 0.8% dash of Iberian but that’s not unusual for a person of Irish descent. It’s the remnant of an ancient migration.

I can also follow my maternal DNA back through time to see the beginning and end of a migration into Europe. DNA comes from both of your parents but you get mitochondrial DNA (mtDNA) from your mother. Occasionally, randomly, there is a mutation and new branches of mtDNA form, but the path of descent is still recognizable.

From the path of descent and the average rate of mutation, we can presume that our most recent, common matrilineal ancestor – Mitochondrial Eve – lived about 150,000-200,000 years ago in eastern Africa. She wasn’t the only woman alive at the time but only her descendants survive. All mtDNA descends from her mtDNA, Haplogroup L. Every bit of mtDNA emerging outside of Africa comes from a woman or women in Haplogroup L3, who were part of an African diaspora 65,000 years ago.

My mtDNA is R0 (L > L3 > N > R > R0)

It emerged in a woman about 40,000 years ago on the Arabian peninsula. Her descendants spread across the Middle East, Europe, northern Africa and western Asia.

R0 has given rise to 1,350 subtypes of mtDNA, and over half of people in western Europe descend from one of those subtypes. But R0 is rarely found in Europeans anymore – less than 1% of Irish carry it. It is commonly found, however, on the Arabian peninsula – most frequently among the Soqotri of Yemen, about 40.7% of their population is R0.

So the genetic code of my mother, her mother, her mother and so on… ties me in an unbroken chain to a woman who walked out of Yemen and populated Europe.

So why isn’t this blog entirely about Irish ancestors, if I’m mostly Irish?

The short answer is, I can only know what is knowable. I can’t write a history, if there’s no record to tell me what happened. And for most of my Irish ancestors, there’s no record at all.

Starting in 1695, the majority of my ancestors lived under a legal system that prevented them from doing many of the things that normally cause an ancestor to appear in the record. They were prohibited from keeping church registers. They were barred from voting or holding office. They couldn’t serve in the military. If they did own land, laws regarding the sale and inheritance of land made it very unlikely to remain in a Catholic family. So many times, there is just no record to find.

Record keeping, where it did exist, was disrupted by periods of famine and political upheaval. The “Great Frost” of 1740 killed 15-20% of the population in 1 year. There were 24 potato blights before the 1845 Great Hunger which, conservatively, killed 1 million people in Ireland. A further 1.5-2M million emigrated, with 20-50% dying en route, so the total loss of life is probably much higher.

And the records themselves were sometimes casualties of war. In 1922, 2 days into the civil war, the Public Records Office burned to the ground following an explosion in a neighboring building. Census returns for 1813, 1821, 1831/4, 1841, 1851, 1861, 1871, 1881, and 1891, wills and probate records dating to the 16th century, and all court records before 1900 were lost.

Only 14% of all pre-1800 church records survive.

So I write the stories I can write

When you consider the size of a generation, against the number of people I can actually trace, you’ll see how rare it is to be able to tell a story at all. There could be 4096 ancestors in my 10th great-grandparents’ generation. I can only name 53 of them. For 6 of them – all women – I only have a first name.

99.7% of the last 16 generations are unknowable.

	Generation Size	Full Name Known	First Name Known	% of Generation
Parents	2	2		100%
Grandparents	4	4		100%
Great-Grandparents	8	8		100%
2nd Great-Grandparents	16	16		100%
3rd Great-Grandparents	32	25	3	87.5%
4th Great-Grandparents	64	20	1	32.813%
5th Great-Grandparents	128	26	3	22.656%
6th Great-Grandparents	256	20	1	8.203%
7th Great-Grandparents	512	25	2	5.273%
8th Great-Grandparents	1024	36	2	3.711%
9th Great-Grandparents	2048	49	1	2.441%
10th Great-Grandparents	4096	47	6	1.294%
11th Great-Grandparents	8192	47	2	0.598%
12th Great-Grandparents	16384	17	1	0.110%
13th Great-Grandparents	32768	4		0.012%
14th Great-Grandparents	65536	1		0.002%