Ancient Chilean Mummies Provide First Genetic Proof Smallpox Came from Europe

Researchers analyzing DNA from two naturally mummified individuals in northern Chile have produced the strongest genetic evidence to date that smallpox was introduced to the Americas through European colonization. The study, published in Science on 30 July 2026, examined bone samples from an archaeological site at Camarones and identified smallpox virus DNA in remains dated between 1492 and 1631. The two individuals, an adult man and woman aged 18–35, likely died from the infection.

Genetic analysis revealed that the Chilean smallpox strain, designated CAM9 by researchers, fits precisely between medieval European virus strains and later variants, confirming a European origin. Geneticist Shigeki Nakagome of Trinity College Dublin stated the findings provide "a better picture of how it reached remote populations through colonization." The virus genomes recovered from both individuals were almost identical, suggesting concurrent infection. Scientists also documented that the virus evolved over centuries, losing certain genes as it adapted to human hosts—a mechanism potentially relevant to understanding modern related viruses such as mpox.

Historical records have long documented smallpox's catastrophic impact on Indigenous populations in the Americas, with estimates suggesting approximately 4 million Indigenous deaths after European arrival. However, this genetic evidence represents only the third known pre-20th-century smallpox genome sequence in the archaeological record, following seventh-century Viking remains and a seventeenth-century Lithuanian mummy. The discovery was made while researchers were initially testing DNA analysis methods on archaeological samples from the Chilean site.

The study raises new questions about transmission routes. While European exploration and settlement following Christopher Columbus's 1492 Caribbean voyage and Amerigo Vespucci's South American expeditions remain primary suspected sources, researchers note the disease could have also spread through African populations connected to the slave trade. The identification of smallpox in a remote South Chilean region with no previously documented disease record suggests the virus may have spread along pre-existing Indigenous trading networks.

Biologist Patricia Foster of Indiana University, who reviewed but did not participate in the research, stated: "Nobody would ever question that smallpox came to this hemisphere from colonization, but this proves it." Study coauthor Constanza de la Fuente Castro, a biological anthropologist at the University of Chile, emphasized the significance: "It wasn't just cultural or demographic. It's literally written into biological evidence that we can still recover and read today." The research also documents how viral mutation rates changed over time, slowing in the centuries following introduction to the Americas before accelerating again in the nineteenth century—a pattern researchers suggest may relate to widespread vaccination campaigns.