Ancient DNA Reveals millennia of Human-Microbe Interactions & The First Epidemiological Transition
Around 10,000 years ago, the shift from hunter-gatherer lifestyles to agriculture and settled communities dramatically altered the relationship between humans and infectious diseases. This period, known as the First epidemiological transition, saw a rise in mortality due to infections as growing populations and closer proximity facilitated microbe transmission. Recent research utilizing ancient DNA is now painting a detailed picture of this transition, revealing the long history of several key pathogens.
Scientists have identified evidence of diseases circulating far earlier and more widely than previously understood. A study analyzing ancient genomes uncovered 42 cases of Yersinia pestis, the bacterium responsible for plague, dating back as far as 5,700 years ago across regions including Russia, Central Asia, and Siberia.This demonstrates the plague wasn’t limited to isolated outbreaks, but was actively circulating throughout Eurasia. Evidence of localized outbreaks was also found in the form of groups of individuals buried together, all infected with the disease, alongside medieval cases identified in Denmark.
Beyond plague, the research highlighted the prevalence of other pathogens. Borrelia recurrentis, the bacterium causing recurring fever transmitted by lice, was detected in 34 individuals across Eurasia, with the oldest case found in a Neolithic farmer in Scandinavia. This disease thrived in the crowded and unsanitary conditions associated with early agricultural settlements. Malaria, specifically Plasmodium vivax, was also identified in individuals spanning the Bronze Age to the Viking era, confirming its long-standing presence in Europe and Asia.The hepatitis B virus was found in 28 individuals, some dating back 9,000 years in Siberia, and even the common Teno virus, which currently infects 80% of the human population, was identified in ancient samples.
Notably, researchers discovered instances of coinfection - 15 cases where individuals were simultaneously infected with multiple diseases. A viking from Norway, such as, carried both smallpox and leprosy, while a Danish individual was infected with leprosy and leptospirosis. These combined infections likely exacerbated illness and increased mortality rates.
This research exemplifies the emerging field of genomic paleoepidemiology, which aims to map the spatial and temporal distribution of pathogens throughout human history. As more ancient specimens are analyzed and integrated with archaeological, genetic, and environmental data, this map will become increasingly comprehensive, offering crucial insights into how microbes have evolved alongside and impacted human societies over millennia. Each new biological sample analyzed represents another piece of the puzzle, revealing the complex and enduring relationship between humans and the microbial world.
