The genes of prehistoric farmers may have diversified and mutated to facilitate farming lifestyles, according to researchers from the Francis Crick Institute.
Immunity genes may have been strengthened by the diversity brought in by Neolithic farmers, which resulted in the transition to farming lifestyles in prehistoric periods.
These immunity genes allowed for responses to disease, as opposed to the previous belief that the transition to farming lifestyles – from hunting and gathering – during this period was due to increased natural selection on immunity variants, as people started to live closer to animals and eat more animal products.
Research
The London-based research institute said that one of its studies found Neolithic farmers from the Near East who came to Europe about 8000 years ago mixed with Mesolithic hunter-gatherers already in Europe and that this was responsible for the diversified and strengthened immune responses to disease.
The patterns discovered by scientists indicate that genetic variants present in Mesolithic hunter-gatherers were passed down.
Researchers were interested in whether any particular genes might have coded for adaptations that were important to early farming groups, like immunity to diseases, and looked for evidence of rapid evolution in these populations.
However, scientists said this research shows that diversity in immunity genes may be just as important as adaptation to lifestyle.
The research team speculates that either the hunter-gatherers already had genetic adaptations against bacteria, viruses or other microorganisms in Europe, or that having many different forms of the genes (from mixing with Neolithic farmers) was advantageous for survival.
Researchers at the ancient genomics laboratory at the Francis Crick Institute studied DNA from 677 individuals dating to Stone Age Europe, spanning the movement of Neolithic farmers to Europe where they mixed with the Mesolithic hunter-gatherers.
Prehistoric farming
About 20% of the ancestry of descendant late-Stone Age people could be traced to the local European hunter-gatherers, which prompted the researchers to ask whether any particular genes showed evidence of more hunter-gatherer ancestry.
Tom Davy, PhD student at the Francis Crick Institute and lead author, said: “It was really exciting to see for the first time that immunity is important for the transition to farming in a prehistoric population.
“The later Neolithic people had far more farmer ancestry in general, so we expected to see the same at the MHC (major histocompatibility complex) region, especially as many diseases have been linked to Neolithic periods.
“But we saw about 50:50 ancestry from Neolithic farmers and Mesolithic hunter-gatherers here, showing that natural selection favoured genes from the hunter-gatherers already in Europe.”
Davy said researchers are not sure why this happened yet, but one proposal is that the European hunter-gatherers had genetic variations which allowed them to fight off diseases that were specific to Europe.
“Or picking up a variety of genes from both hunter-gatherers and farmers was beneficial because it resulted in lots of diversity at this major group of genes, allowing people to better fight off disease,” he explained.
Pontus Skoglund, group leader of the ancient genomics laboratory at the research institute, said: “The shift to farming was an important transition all over the world, resulting in changing diets and exposure to infectious disease.
“Previous research has suggested that adaptation in genetic regions relating to immunity, such as the MHC, has been important in recent time periods, and this research now provides similar evidence for adaptation in prehistory.
“By growing the ancient genomic record, we will be able to better understand the role of immunity in other periods of the human past.”