The Genetic Roots of the British Isles

Back in 2008 I listening to the audiobook version of Saxons, Vikings, and Celts: The Genetic Roots of Britain and Ireland by Bryan Sykes, a professor of human genetics at Oxford University. In it he described how he had created "genetic archaeology", which uses genetic sequences to trace the origins of modern humans, and how he and a number of other researchers performed a survey of the British Isles to determine the origins of the modern British, Irish, Welsh, and Scottish peoples.

He used two sources for his genetic sequences. One was mitochondrial DNA, or mDNA; the other was the Y-chromosome, or yDNA. Mitochondria are tiny organelles that live inside cells. They have their own DNA, which is inherited through sex like chromosome genes. However, mDNA is only inherited from the mother. This is because the egg is filled with mitochondria -- it has the most of any cell in the body -- while the sperm has very few. These are located in a collar behind the head where the tail attaches, and are usually discarded after the sperm penetrates the egg membrane. Even if the collar gets absorbed as well, those mitochondria are so few that their DNA barely registers compared to the overwhelmingly huge amount of egg mDNA. As such, we all inherited our mDNA from our mothers, who inherited it from their mothers, who inherited it from their mothers, all they way back unbroken into the depths of the past.

Unlike mitochondria, only men have the Y-chromosome, but like mDNA, men only inherit yDNA from their fathers. They in turn inherited it from their fathers, who inherited it from their fathers, once again in an unbroken line back through the mists of time.

In this way, Sykes and his colleagues are able to determine which matrilineal and/or patrilineal clan any individual belongs to throughout the world. This also allowed them to establish the true genetic origins of modern Europeans and the peoples of the British Isles. While much of what they learned supports modern archaeology and anthropology, some surprises did spring up.

Perhaps the most profound discovery was that the mDNA demonstrated that all modern Europeans were descended from eight matrilineal clans. These clans are ancient; one is as old as 45,000 years, and all save one is older than 12,000 years. This in turn indicates that 88% of modern Europeans are descended from Late Paleolithic and Mesolithic hunter/gatherers. Up until then, archaeologists and anthropologists assumed that modern Europeans were descended from Neolithic farmers migrating out of the Middle East, and that they had overwhelmed and forced out the hunters. However, the genetic results indicate that only 12% of Europeans are directly descended from the farmers. This establishes that the farmers and the hunters co-existed peacefully for much of prehistory, and rather than being supplanted by farmers, the hunters adopted farming techniques.

This same pattern is seen in the British Isles, where the matrilineal clans demonstrate that the genetic roots of the modern British, Irish, Welsh, and Scottish peoples were established by 10,000 years ago at least, but there the big surprise was that Celtic ancestry forms the genetic bedrock of the islands.

At this point we need to be careful about what we mean by Celt. Genetics can tell us nothing about culture, so Sykes is not saying that these early people had the same language and culture as the Iron Age Celts. What he is saying, however, is that the same matrilineal clans that make up the genetic roots of the Irish and the Welsh also form the basis for the genetic roots of the British. With two exceptions, you can go anywhere in the British Isles and be virtually certain that the matrilineal ancestry of any person is Celtic.

The exceptions are the northern islands like the Shetlands and the Orkneys, and eastern Britain. There you have almost a fifty percent chance, give or take, of finding people who are descended from Scandinavian women. It is virtually impossible to distinguish between Vikings, Danes, and Normans by looking at genetic sequences; however, history and archaeology support the speculation that the Danes and the Normans did not import large enough numbers of their women to displace the native Celtic women, while the Vikings did.

Particularly surprising, however, is that there is no evidence of Saxon ancestry in the mDNA. This suggests that the legendary history of Britain is true, that the Saxons did not colonize Britain as many scholars have thought, but rather conquered it and then took local women for wives. Another surprise is that the Picts of Scotland, rather than being an isolated ancient people with nothing in common with the native islanders as some people have speculated, are in fact virtually indistinguishable from the Celts.

The genetic sequences of the founding clans of the British Isles indicate that most of the people came through the Mediterranean up the Atlantic seaboard through Ireland and Scotland, while others came across from northern Europe into southeastern Britain. There is no evidence for an influx of people from central Europe, then or later. What this seems to tell us is that the prevailing theory for how the Celts reached the British Isles, as a migration from central Europe between 500 and 200 B.C.E., is incorrect. Instead, what seems to have migrated was the language and the culture, possibly through trade. The genetic evidence cannot rule out the possibility of small migrational movements, but it can rule out a huge migration or conquest that would have displaced the older matrilineal clans. If there was any kind of migration, it left no traces in the genetic sequences of the modern people of the British Isles.

The yDNA sequences for the most part support the conclusions based on the mDNA sequences. Five patrilineal clans dominate the ancestry of modern Europeans, with three making up virtually all of the ancestry of the British Isles. Again, the Celtic clan predominates, though this time the Scandinavian clan and a Germanic clan form higher percentages, particularly in Scotland and eastern Britain. Here is where we find Saxon ancestry, though we still cannot distinguish between Viking, Dane, and Norman yDNA.

However, we can trace family names, and here the evidence compliments the genetic sequences beautifully: wherever you find a preponderance of Norman, Norse, or Danish family names, you find a preponderance of Scandinavian yDNA, and where you find Saxon family names, you tend to find Germanic yDNA (though the Saxons also have some Scandinavian ancestry as well).

The one major surprise to come out of the yDNA data, though, is that there is very little variation in local paternal sequences. This is in sharp contrast to the mDNA, which often has large variation in local maternal sequences. The variations come from mutations, and it is a truism that the longer a DNA sequence exists, the more mutations it will acquire and thus the greater the variation it will display within a local population.

yDNA does not violate this truism; in fact, it mutates even faster than mDNA, so at first Sykes and his people thought the patrilineal clans were very young, at best only a few thousand years old. Then they realized that what they were seeing was the Genghis Effect. This phenomenon is named after the Genghis Khan, who, when he invaded a new territory, killed as many men as he could catch and impregnated as many women as he could find. As a result, his unique yDNA sequence tended to predominate within that territory's male population, at the expense of the local, more varied yDNA sequences.

Sykes realized that the same thing had happened in the British Isles, that the low variation in the yDNA sequences indicated the success of a few powerful men in spreading their own yDNA widely throughout a local population. A classic example is the yDNA sequence that dominates the O'Neill clan and its offshoots. A significantly large number of men with O'Neill family names all over the world have this sequence; only the sequence attributed to the original Genghis effect occurs in more men. The one exception to this is the male population of the area of central Scotland called Pictland. There the yDNA is almost as varied as the mDNA, but this is explained by the fact that inheritance among the Picts was matrilineal, including chiefdoms and kingships. As such, there was never a chance for one male lineage to dominate.

As fascinating as all this is, it's main impact as far as the Medb hErenn universe is concerned is that it establishes a scientific basis for my fictional idea that the modern Irish are descended from a stock of ancient people who absorbed various invaders over the millennia without being drastically changed. I will explain more about this on the website when I post my page on the Hibernians.