- Ancient DNA from two individuals in northern Chile provides the first direct genetic link between colonial-era smallpox outbreaks in the Americas and Old World virus strains.
- The reconstructed smallpox genomes from the Americas suggest that Europeans likely brought the disease during the colonial era, with the viruses belonging to an extinct branch of variola virus.
- The study highlights how ancient DNA can help answer questions about the impact of colonization, population change, and vaccination on the evolution of diseases like smallpox, shedding light on the devastating effects of European contact on Indigenous populations in the Americas.
Ancient DNA from two people buried in northern Chile is helping answer one of the most painful questions in the history of the Americas: how smallpox arrived after European contact.
Researchers say the newly recovered genomes provide the first direct genetic link between colonial-era outbreaks in the Americas and Old World strains of the virus
What happened?
In work published in Science, as a Trinity College Dublin team reconstructed ancient smallpox genomes from the Americas for the first time, giving further evidence for the argument that Europeans brought the disease during the colonial era
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The outlet noted that the DNA studied came from the remains of two people from a community in northern Chile, dated to sometime between the late 1400s and the early 1600s
The team found, as that the viruses belonged to an extinct branch of variola virus, the pathogen that causes smallpox. Researchers said this lineage appears to have evolutionarily developed between medieval European forms of the virus and strains seen in later centuries
Bruno Romero González, a Ph.D. student in Trinity’s School of Medicine, said, as The Express reported, the results show how “major historical events including colonization, population change and vaccination likely shaped the evolution” of the disease
He added that the work shows how ancient DNA can help answer longstanding questions that written records alone cannot fully resolve
Why does it matter?
Across the Americas, Indigenous populations suffered devastating losses after European contact, and smallpox was one of the diseases central to that collapse
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Scholars have long argued that pathogens carried across the Atlantic transformed societies throughout the hemisphere, yet they lacked molecular evidence tying smallpox in the colonial Americas to older Old World virus lineages, The Express reported
The new evidence helps fill that gap. It also suggests that disease evolution is not just a biological story, but one shaped by migration, colonization, immunity, and public health
Dr. Lara Cassidy of Trinity’s School of Genetics and Microbiology said the virus changed over a long period until the 1500s and then evolved more slowly through the 1600s and 1700s, when colonial expansion and major epidemics were underway
The researchers said that pattern may reflect a period when the virus had become especially effective at spreading through populations with little prior immunity.
What’s being done?
The study adds to the growing field of ancient pathogen genomics, in which researchers use fragments of old DNA to reconstruct how diseases spread and changed over time. That can sharpen historians’ understanding of past epidemics while also giving modern scientists clues about how infectious diseases adapt
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Public health measures can shape the course of disease, sometimes in ways that become clear only years later
The Express also reported that researchers found signs that smallpox’s evolutionary pace may have picked up again during the 1800s as vaccination spread and immunity increased
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