Slicing Cheddar Man down to size

Who is Cheddar Man, and what’s up with the name?

Over the past week or so there has been a lot of talk about “Cheddar Man.” It turns out that the cheese and the man come from the same area, the Cheddar Gorge. At 9,150 years old, Cheddar Man is the most ancient complete human skeleton we have from Britain. Though some might call him the “first Briton,” there are human finds which indicate that the ancestors of this individual arrived thousands of years before his death.

Cheddar Man was a hunter-gatherer. Part of a Mesolithic tradition that expanded from the south after the last Ice Age, and extended from the southwest corner of the continent, northward to Scandinavia. Cheddar Man and his people shouldn’t be viewed in isolation, but as part of a whole tradition.

Fascinating aspects of Cheddar Man transcend archaeology and paleontology and into genetics. In the late 1990's, Oxford geneticist Bryan Sykes attempted to extract the mitochondrial DNA from Cheddar Man, because the remains were in good enough condition that he thought it was feasible. Mitochondrial DNA is copious, and therefore a good target for any preliminary method.

It turns out that Cheddar Man carried haplogroup U5, found in ~10% of modern Europeans, and U5 is still found in present-day Britons living near Cheddar Gorge. The media ran away a bit with the story, and “descendants of Cheddar Man” have become somewhat famous.

The backstory, though, is that many people were suspicious of the finding because they believed that there was contamination in the laboratory. The Cheddar Man results were never put through the peer review process, and remain more lore than (scientific) literature.

Today we live in a different time from Cheddar Man’s first discovery. Paleogenetics is now an established and technologically advanced field. The whole genome of Cheddar Man, not just the mtDNA, has now been analyzed in a new preprint, Population Replacement in Early Neolithic Britain. Did you notice that the title of the preprint didn’t mention Cheddar Man? That’s not a coincidence!

But first, it needs to be mentioned that Cheddar Man also got the star treatment on Britain’s Channel 4 with a whole special that focused on his physical appearance. Titled The First Brit, one aspect of Cheddar Man that received much attention in the documentary was his physical appearance. Because they had his whole genome, they could look at genetic variants associated with pigmentation differences in modern Europeans. From that, they concluded that Cheddar Man had light, perhaps blue, eyes, and dark brown skin.

This is not a surprising conclusion, but neither is definitive. Predictions are predictions, and because we don’t have a time machine, we’ll never be able to verify this particular one. There has to be appropriate humility about our confidence in any given prediction.

But perhaps the biggest issue with this prediction is that we know that pigmentation is a complex trait with diverse genetic architectures across human populations. More concretely, populations can be light-skinned or dark-skinned in different ways. The populations used in the “training set” for the algorithm used to predict Cheddar Man’s skin color were necessarily modern ones, because those are the ones we can see to confirm the trait in question. Cheddar Man was very different from modern Europeans genetically, so one should always be careful about assuming that forensic predictions can tell us about him.

What we do know is that most high-latitude populations outside of Europe are lighter in complexion, but not quite as pale as Europeans. Some of the people can be accurately described as brown in skin tone, while the people of Tasmania were dark brown. Combining genetics and ethnography, I think it is reasonable to say that Cheddar Man was noticeably darker skinned than typical modern Britons, but we need to hold off on being confident as to whether he was dark, medium or light brown.

As I hinted above, the curious aspect of the science of the Cheddar Man research team isn’t Cheddar Man at all: the title of their preprint focuses on the Neolithic, not the Mesolithic. Why? Because the data set that they are focusing on has six Mesolithic samples, like Cheddar Man, but 67 Neolithic ones. What they discovered was massive population replacement in Britain at the boundary of the Mesolithic/Neolithic, around 6,000 years ago.

In fact, it is possible that no Briton alive today is a direct descendant of Cheddar Man!

So why is the media saying that 10% of the ancestry of modern Britons derives from Cheddar Man and his people? Because Western European Mesolithic hunter-gatherers (WHG) were all very genetically similar, derived from a single population that expanded into a largely empty landscape after the last Ice Age. About 10% of the ancestry of Britons does seem to derive from these WHG populations…but that may have been on the continent of Europe, and not Britain itself (though they did find some evidence of mixture of farmers with local people in Scotland and eastern England in particular). The statistical genetics does not allow us to evaluate which model is correct to a high confidence. At least for now.

What both genetics and archaeology suggest is that the transition from hunting and gathering to farming in Britain was relatively rapid. And this is evident in the genetic data, which does not exhibit the same evidence of delayed mixing between hunter-gatherer populations and farmers after the initial contact — as occurred on the continent of Europe.

So who were these first farmers? How did they relate to Cheddar Man and his people, and to subsequent Britons, down the present day? The short answer is that the first farmers in Briton were genetically very similar to modern day Sardinians, who preserve some unique characteristics isolated in their island fortress. The Sardinians in their own turn are descended from ancient Anatolian farmers from the Middle East.

These people, early European farmers, or EEF, pushed west across the Mediterranean and up through the fertile valleys of Central Europe. They gave rise to the Cardial culture in Southwest Europe, and the Linear Pottery culture in Central Europe. The genetic differences between them and the WHG were stark, about the same as what distinguishes modern Northern Europeans from Han Chinese. Though the farmers and WHG populations eventually mixed into one populations, probably with the farmer culture dominant, they remained distinct in both genetic and archaeological records for many centuries.

The results from the data above indicate that it is more likely that most of the ancestry of British Neolithic farmers was more closely related to the agricultural expansion into the Western Mediterranean, as opposed to the one into Central Europe. That is, the British Neolithic may have roots in the same movement that resulted in the Cardial culture thousands of years before, and gave rise to the Neolithic societies of Iberia and southern France.

So like continental Europe, the history of Britain is one of rupture, change, and genetic revolution.

The farmers who arrived in Britain 6,000 years ago flourished for 1,500 years. It is these people who laid the foundations for Stonehenge, 5,100 years ago. Cheddar Man may have been the “first Briton” as a matter of precedence, but the main genetic and cultural imprint belongs to later generations.

And yet the farming peoples too would pass into the shadows of history, as ~4,500 years ago a new group arrived, the Bronze Age “Bell Beaker” culture — so-called because of their bell-shaped pottery. Though the culture of the Bell Beakers began in Iberia, genetically the people who brought it to Britain seem to have been Central Europeans, with connections to a massive inflow of peoples from the borderlands between the Eurasian taiga and steppe to the east, which some have suggested were connected to the spread of Indo-European languages.

These are the people who are closest genetically to modern Britons, whose heritage is the predominant pattern across the island from Scotland to Cornwall. The genetic data indicate that the Bell Beaker migration contributed ~90% of the ancestry to the people who lived just less than 4,000 years ago.

Cheddar Man was the first, but the Bell Beakers were the last major wave demographically (the Anglo-Saxon and Viking migrations also had an impact, but never became predominant in most of modern day mainland Britain).

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