Smallpox, a disease that claimed millions of lives before its 1980 eradication, left a devastating mark on the Americas following the onset of European colonisation. While historical records indicate the first outbreak occurred during the 1518 Spanish conquest of the Caribbean, new research published in the journal Science provides definitive biological evidence of how the virus reached remote regions of South America.
Researchers from Trinity College Dublin analyzed 13 bone samples recovered from an archaeological site in Camarones, northern Chile. The study successfully identified smallpox DNA within the leg bone fragments of two individuals—an adult man and woman aged between 18 and 35. By dating these remains, scientists concluded that the pair likely died between 1492 and 1631. This discovery is significant because it provides the strongest genetic link to date between smallpox strains in the Americas and those that circulated in Europe during the medieval period.
According to the study, the virus found in the Chilean samples sits genetically between medieval European strains and later variants, confirming its origins. Patricia Foster, a biologist at Indiana University who was not involved in the research, noted that while the arrival of smallpox via colonisation was historically accepted, this finding provides the necessary molecular proof. Constanza de la Fuente Castro, a biological anthropologist at the University of Chile and a coauthor of the study, emphasized that the impact of the disease is now permanently recorded in biological evidence, illustrating how it decimated Indigenous populations and left them vulnerable to conquest.
The exact path the virus took remains a subject of ongoing investigation. While settlers arrived in multiple waves following the explorations of Christopher Columbus and Amerigo Vespucci, the researchers noted that the virus might also have spread through Africa via the transatlantic slave trade. Furthermore, the presence of these infections in a remote area with no prior history of the disease suggests that the virus may have traveled through established Indigenous trading networks.
Beyond confirming the origins of the outbreak, the research allowed scientists to observe the evolution of the smallpox virus over time, including the loss of specific genes that may have assisted its adaptation to human hosts. This study offers a sobering look at how a single pathogen altered the demographic and cultural landscape of an entire hemisphere.
“It wasn't just cultural or demographic. It's literally written into biological evidence that we can still recover and read today,” de la Fuente Castro said.
