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Early European farmers survived because they had lots of sex

The findings are based on remains dating back around 8,000 years.

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(Photo by Jake Heinemann via Pexels)

By Mark Waghorn via SWNS

Early European farmers survived because they had lots of sex – with hunter-gatherers, according to new research.

An analysis of ancient genomes shows the opposing cultural groups were much closer than previously believed.

It identified gene changes that boosted fitness - due to interbreeding. The findings are based on remains dating back around 8,000 years.

There was more hunter-gatherer ancestry in the mixed population than would be expected by chance.

In particular, differences were traced back to areas of DNA called the major histocompatibility complex (MHC) - which protects against disease.

The international team also detected farmer ancestry in a gene called SLC24A5 which affected hunter-gatherers' skin color, which was typically dark.

Lead author Tom Davy, a Ph.D. student the Francis Crick Institute's Ancient Genomics Laboratory in London, said: "This tells us these regions of the genome were experiencing natural selection.

"The genetic variants predominantly carried by hunter-gatherers in the MHC region and by farmers in SLC25A5 increased in frequency in the descendant population."

Agriculture, of course, gets more food for less work. But initially, ditching foraging might have been bad for Stone Age man's health.

It emerged in the Middle East and Britain around 10,200 and 6,000 years ago, respectively.

It is difficult to envision a world without farms. But as recently as 10 millennia ago, only in the Middle East had people turned from hunting and gathering. The effect has fascinated public health experts for decades.

Diets became monotonous, and a narrower range of food courted disaster from failed harvests.

More people packed together for longer periods increased the risk of disease from contaminated water, food and soil.

Social mechanisms developed to adjudicate disputes, dampening tensions that could tear communities apart.

People had to defend themselves, their land and stored food from neighboring groups because it was no longer easy to move away from sources of conflict.

Interbreeding would have ensured offspring had a wider range of immune responses - and greater protection against infection.

The study in Current Biology suggests it resulted in "mosaics of genetic variation" that were acted upon by natural selection.

It is a process through which all organisms, including humans, adapt and change over time.

The MHC comprises a cluster of genes that code for surface proteins on cells - helping our immune system recognize pathogens.

The researchers mapped the genomes of 677 prehistoric individuals.

Co-author Dr. Pontus Skoglund, of the University of Pennsylvania, said: "A longstanding idea is farming lifestyles drove immune adaptation due to denser settlements, new diets, and proximity to livestock.

"When farming groups expanded from the Near East into Europe and mixed with local hunter-gatherers, the natural prediction would be that the farmers' immunity genes would be best adapted to the farming lifestyle and thus selected for.

"However, we see the opposite, that hunter-gatherer ancestry is enriched at the MHC immunity locus. This could, for example, be because the hunter-gatherers were already adapted to pathogens found in Europe, or it could be the result of natural selection favoring diversity in immunity genes."

As for changes in pigmentation, earlier studies also had shown selection for reasons that aren't fully understood.

Co-author Dr. Ian Mathieson, also from the Francis Crick Institute, said: "One hypothesis is lighter skin pigmentation allowed farmers to synthesize more vitamin D from ultraviolet radiation, while hunter-gatherers were able to obtain sufficient vitamin D from their diet."

The shift to an agricultural lifestyle was a fundamental transition that happened worldwide in human history.

Added Dr. Skoglund: "This study revealed natural selection during the agricultural transition in one region of the world, Europe, but other regions are not well understood.

"Future ancient-DNA studies will also be able to address to what extent immunity was a key target also in other periods of environmental and lifestyle change during human evolution."

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