Major migrations to Europe over the last 45,000 years helped shape modern Europeans’ risk of Type 2 diabetes and Alzheimer’s disease. Two articles detailing the findings were published in the journal Nature. The publications include an analysis of DNA from the bones and teeth of hundreds of ancient people. The oldest data dates back to the Mesolithic period (or Middle Stone Age). Scientists compared those ancient genomes with the genomes of modern Europeans.
What researchers found
The project shed light on the genetic legacy of three ancient migrations to different regions of Europe. This includes the arrival of hunter-gatherers from Asia around 45,000 years ago, Neolithic farmers from the Middle East 11,000 years ago, and herders from the Pontic-Caspian steppe (a region encompassing Eastern Europe and Central Asia) about 5,000 years ago. Overall, researchers compared the genomes of 1,750 ancient individuals with the genomes of approximately 410,000 white British individuals. The data were stored in the UK Biobank. The study’s authors calculated how much ancient DNA modern Britons inherited, as reported by Live Science.
Scientists identified gene variants associated with multiple sclerosis (MS) that were carried by farmers from the Pontic steppe. Those farmers primarily migrated to Northern Europe, which helps explain why MS is especially common among people of Northern European descent. The researchers concluded the risk variants were positively selected — they likely provided benefits to the migrants and were favored by natural selection.
Some gene variants involved in immune function increase a person’s susceptibility to MS. These include variants of the HLA genes, which help the immune system detect pathogens. But some HLA variants are also closely linked to autoimmune diseases, where the immune system attacks the body’s own cells.
The authors suggest that in the past, those HLA variants may have helped ancient farmers fight infections transmitted by animals. As hygiene, diet, and medical care changed, those same variants had different effects. Researchers say understanding the evolutionary forces that favored these genes could help in treating MS. “What we need to move towards is an attempt to recalibrate the immune response, rather than completely eliminate it,” said lead author Lars Fugger, a professor of neuroimmunology at the University of Oxford.
Additionally, the authors found that people who carry more DNA from the hunter-gatherer group may have a higher genetic risk of Type 2 diabetes and Alzheimer’s disease. Modern populations with that ancestry mostly live in Eastern Europe. Risk variants for Alzheimer’s disease may have been positively selected as well. For example, the ApoE4 variant increases Alzheimer’s risk but may also boost fertility in women.
