DNA reveals origins of farming in Britain

18 April 2019

Stonehenge

Neolithic British Structure

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A new study of the DNA of ancient late-stage hunter-gatherers, and early-stage farmers has shed light on the arrival of agriculture in Britain, revealing that the technology was imported by migrating farmers, rather than being adopted by the indigenous hunter-gatherer population, clearing up years of debate.

Around 6000 years ago, Britain underwent a major cultural change, which archaeologists refer to as the shift from “mesolithic” society, which saw loose affiliations of humans who survived by hunting and gathering, to “neolithic” society, which saw the rise of farming and agriculture.

“Farming first developed over 10,000 years ago in the middle east...somewhere near modern-day western Turkey”, explains Professor Mark Thomas of University College London, an author of the new study published in Nature Ecology & Evolution.

Fascinatingly, agriculture appears to have spread throughout Europe reaching the north-western coast of the continent around 7000 years ago. Then, in a turn of events that has puzzled archaeologists for decades, the spread seems to have taken a 1000 year hiatus before crossing the channel.

This large gap has led to debate as to whether farming was imported to Britain by a genetically distinct population of farmers, who had already developed the technology elsewhere (as was known to be the case in mainland Europe), or whether the extended delay pointed to the fact that the existing population had slowly adopted the technology over time.

“We obtained DNA from early farmers in Britain... but also from six mesolithic hunter-gatherers, the people that were there before farming came.”

They found that the genome (a representation of a person’s entire genetic code) of the early farmers was quite distinct from the genome of the late hunter-gatherers. Further, they found that the early farmer genomes were extremely similar to the genomes of farmers from mainland Europe around the same time.

“That tells us that farming was brought to Britain by migrating farmers”, says Thomas. The study found that the migrating group (probably from near modern-day Spain) rapidly replaced the existing hunter-gatherer population.

Furthermore, the DNA indicates a low level (if any) of interbreeding between the migrating farming population and the hunter-gatherers. This is different from mainland Europe, where the genomes indicate that as farmers migrated from the middle east, they interbred with the existing populations.

Thomas points to the 1000 year hiatus as a possible explanation for the difference.

“There is some evidence that the first farming populations spreading throughout Europe, they were having a pretty tough time.” This means that expansion, and population growth were likely slow, leading to a higher degree of mixing with the existing populations.

“By the time they’d been there [on the coast of the mainland] 1000 years, they’d got used to it”, explains Thomas.

This would have left them “better adapted” for survival in Britain, allowing their population to rapidly expand on the isles, effectively replacing the existing population by sheer weight of numbers.

According to Thomas, this result informs a wider debate in archaeology about whether the spread of ideas, or the migration of populations is the primary factor behind social changes.

Thomas claims that as ancient DNA analysis improves, the evidence continues to suggest that most large cultural shifts  throughout human history are associated with significant, rapid changes in genetics, pointing towards migration as the primary driver of societal change.

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