New revelations from ancient DNA analysis have provided insights into the heightened susceptibility to diseases such as multiple sclerosis (MS) among certain populations, shedding light on the impact of ancient migrations. The research, led by University of Copenhagen paleogeneticist Eske Willerslev, examines genetic data from ancient skeletons, uncovering a link between the Bronze Age movement of the Yamnaya people and an increased risk of MS in present-day Scandinavians.
The Yamnaya, who migrated from the steppes near the Black Sea about 5000 years ago, introduced not only a different way of life but also genes associated with a higher likelihood of developing MS. This finding challenges previous speculations about the role of "Viking genes" or environmental factors in Northern Europe.
Willerslev's research extends beyond MS, encompassing a comprehensive genetic survey of early Europeans. By analyzing the whole genomes of over 1000 ancient individuals and comparing them with modern DNA from the UK Biobank, the team explores how ancestral proportions predict variations in disease risk, physical attributes, and more in present-day Europeans.
Contrary to expectations, the study reveals that anti-infection adaptations, including those related to immune response regulation, proliferated thousands of years after the arrival of the first farmers, in individuals with substantial Yamnaya ancestry. This challenges the conventional notion of a continuous arms race between the human genome and pathogens during the Neolithic period.
A recent preprint from the same research team suggests that the timing of diseases coincided with the Yamnaya migrations, indicating that the incidence of diseases transmitted from animals to humans surged during this period. The steppe herders might have maintained animals at higher densities, slowing the spread of diseases in early Neolithic communities.
The link between Yamnaya ancestry and autoimmune diseases like MS is attributed to genes that once enhanced immune responses to pathogens but now contribute to the risk of autoimmunity. This shift in disease prevalence aligns with changes in living conditions, such as improved sanitation and the advent of vaccines.
By comparing ancient samples with the UK Biobank's extensive dataset, the researchers track the emergence of various traits in ancient populations and delve into the selective pressures shaping these characteristics. For example, genetic variants associated with a higher risk of diabetes and high cholesterol, prevalent today, were more common in samples from about 12,000 years ago, likely aiding ice age hunter-gatherers in surviving famine.
The studies not only contribute to a deeper understanding of ancient population dynamics but also hold implications for modern precision medicine. The abrupt and thorough replacement of populations observed in some regions challenges the notion of peaceful encounters during migrations, revealing parallels to historical events like Europeans entering the Americas.
While the focus of this research is on Europe, the increasing availability of ancient DNA samples from other regions could facilitate similar studies worldwide, offering a broader perspective on the impact of ancient populations on contemporary health and genetic diversity.
