Ancient DNA Reveals millennia of Human-Microbe Interactions & The First Epidemiological Transition
Around 10,000 years ago, the shift from โhunter-gatherer lifestyles to agriculture and settled communities dramatically altered the relationship between humansโค and infectious diseases. This period, โขknown as the โฃ First epidemiological transition, saw a rise in โฃmortality due to infections as growing populations and closer proximity facilitated microbe transmission. Recent research โฃutilizing ancient DNA โis now painting a โคdetailed picture ofโ this transition, revealing the long history of several key pathogens.
Scientists โhave identified evidence of diseases circulating โfarโ earlier and more widely than previously understood.โ A โstudy analyzing ancient genomesโ uncovered 42 cases of Yersinia pestis, the โขbacteriumโค responsible for plague, dating back as far as 5,700 years ago โขacross regions including Russia,โฃ Central Asia, and Siberia.This demonstrates the plague wasn’t limited to isolated outbreaks, but was actively circulating throughout โฃEurasia. 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.
Beyondโข plague, the research highlighted the prevalence of other pathogens. Borrelia recurrentis, the bacterium causingโฃ recurring fever transmitted by โlice, was detected in 34 individuals across Eurasia, with the oldest case found inโค a Neolithic farmer in Scandinavia. This disease thrived in the crowded and unsanitary conditions associated with early โฃagricultural settlements. Malaria, specifically Plasmodium vivax, was also identified in โindividuals spanning the Bronze Age to the Viking era, confirming its long-standing presence inโฃ Europe and Asia.The hepatitis B virus was found in 28 individuals, some dating back 9,000 years in Siberia, and evenโ the common Teno virus, โฃwhich currently infects 80% โคof โtheโค human population, was identified in ancient samples.
Notably, researchers discovered instances of coinfection โ- 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 andโ leptospirosis. These combined infections likely exacerbatedโ illness and increased mortality rates.
This research exemplifies โขthe emerging field of genomic paleoepidemiology, which aims to map the spatial and โฃtemporal distribution of pathogens throughout human history. As more ancient specimens are analyzed and integrated with archaeological, genetic, โคand โฃenvironmental data,โฃ this map โฃwill become increasinglyโค comprehensive, offering crucial insights into โขhow microbes have evolved alongside and impacted human societies over โคmillennia. Each newโข biological sample analyzedโ represents another piece of the puzzle, revealing theโข complex and enduring relationship between humans and the microbial world.