Ancient DNA recovered from two individuals in northern Chile provides the first direct genetic link between colonial-era smallpox outbreaks in the Americas and Old World strains, according to researchers publishing in Science and reported by The Express. The findings offer concrete molecular evidence to help answer longstanding questions regarding how the pathogen arrived and evolved following European contact.
Ancient Genomes Map Smallpox Evolution in Colonial Chile
The newly reconstructed genomes come from the remains of two people from a community in northern Chile, dated to sometime between the late 1400s and the early 1600s, as detailed by The Express. According to the research team, these historical samples belong to an extinct branch of the variola virus, which is the pathogen responsible for smallpox. This specific lineage appears to occupy an evolutionary bridge between medieval European forms of the virus and later strains documented in subsequent centuries.
Scholars have long debated the exact mechanics of how European-introduced pathogens decimated Indigenous populations across the Americas. While historical records consistently pointed toward colonial vectors, researchers lacked direct genetic proof connecting colonial-era American outbreaks directly to older European lineages. This newly published genomic data bridges that crucial historical gap, demonstrating how migration, colonization, and shifting immunity directly altered the virus over time.
How Migration and Immunity Shaped the Pathogen
According to Bruno Romero González, a Ph.D. student in Trinity’s School of Medicine cited by The Express, the results illustrate how major historical events like colonization and population changes drove the evolution of smallpox. He noted that ancient DNA successfully resolves historical questions that written records alone cannot fully answer.
Dr. Lara Cassidy of Trinity’s School of Genetics and Microbiology explained to The Express that the virus changed gradually until the 1500s before shifting to a slower evolutionary pace through the 1600s and 1700s. Researchers suggest this stabilization period coincided with intense colonial expansion and widespread epidemics, reflecting a time when the virus optimized for transmission among populations lacking prior immunological defense.
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Researchers also found indications that the evolutionary pace of smallpox accelerated again during the 1800s as vaccination programs expanded and population immunity increased, according to findings covered by The Express.
The Role of Ancient Pathogen Genomics in Historical Research
This study expands the rapidly growing field of ancient pathogen genomics, where scientists extract fragments of old DNA to map out disease transmission routes across centuries. By reconstructing these extinct viral branches, modern researchers gain critical context regarding how infectious agents adapt to public health measures and changing host environments.
While public health interventions continuously alter disease trajectories, genetic evidence shows those shifts often trigger new adaptive responses in viruses over long timelines. The ongoing analysis of historical samples allows epidemiologists and historians to refine models of past epidemics.
Frequently Asked Questions
What did the ancient DNA study discover about smallpox in the Americas?
Researchers reconstructed ancient smallpox genomes from two individuals in northern Chile, providing the first direct genetic evidence linking colonial-era American outbreaks to medieval European strains of the variola virus, as reported by The Express.
When did the individuals studied live?
The remains analyzed by the Trinity College Dublin team date from sometime between the late 1400s and the early 1600s.
How does this research help modern science?
By studying ancient pathogen genomics, scientists can better understand how infectious diseases adapt to human migration, changing immunity, and vaccination efforts over time.
Explore more historical breakthroughs and archaeological discoveries on our Archaeology News page, or dive deeper into genetic research via our Science Updates section.