Researchers Recover Smallpox DNA from Mummies, Revealing Impact of Spanish Conquest on Indigenous Populations
Washington: Recent research has uncovered the first direct molecular evidence of smallpox brought to the New World by Spanish conquistadors in the 16th century. This evidence, derived from the mummies of two individuals who lived in an Inca community in northern Chile, highlights the devastating impact of infectious diseases on indigenous populations during the Spanish colonization of the Americas.
When Spanish explorers arrived in the Americas approximately five centuries ago, they introduced not only weapons and horses but also smallpox and other infectious diseases. These pathogens decimated indigenous populations, who had no prior exposure and thus lacked natural immunity. The researchers recovered ancient viral DNA from the mummies, providing crucial insights into the smallpox outbreaks that led to the deaths of millions in Mesoamerica and South America.
Genetic Analysis of Smallpox Pathogen
The smallpox virus, caused by the variola virus, was analyzed from the remains of the two individuals. The genomic analysis revealed that the strains belonged to an extinct lineage, positioned evolutionarily between known medieval European strains and those that circulated in later centuries. This finding underscores the complex history of the virus as it spread across continents.
The arrival of Europeans in 1492 marked a significant turning point for indigenous populations. Lacking immunity, these communities faced catastrophic population declines due to the rapid transmission of smallpox through person-to-person contact. Bruno Romero González, a geneticist and doctoral student at Trinity College Dublin, noted that the earliest documented smallpox outbreak in the Americas occurred in 1518 on Hispaniola, coinciding with Spanish settlement efforts.
The Scale of Smallpox’s Impact
Smallpox is regarded as one of the most devastating infectious diseases in human history. Shigeki Nakagome, a geneticist and co-author of the study, emphasized that the disease likely affected human populations for at least 1,500 to 2,000 years before its eradication in 1980 through a global vaccination campaign. Prior to this, it was responsible for repeated epidemics worldwide, with estimates suggesting it killed hundreds of millions.
In the Americas, smallpox and other viral diseases are believed to have wiped out approximately 90% of the indigenous population. This demographic collapse facilitated the Spanish conquest of major civilizations, including the Aztec Empire in present-day Mexico, the Maya city-states in Central America, and the Inca Empire stretching from Ecuador to Chile.
Insights from Naturally Mummified Remains
The two individuals whose remains contained the smallpox pathogen were naturally mummified and buried near Camarones Cove in Chile. One was a woman aged 30 to 35, and the other a man aged 18 to 20. Constanza de la Fuente Castro, a biological anthropologist at the Universidad de Chile, explained that the mummies were wrapped in camelid wool blankets and buried with various grave goods, reflecting cultural practices predating the Inca civilization.
While the exact timing of their infection remains uncertain, researchers have narrowed it down to the 16th century, coinciding with the Spanish conquest led by Francisco Pizarro. The psychological impact of smallpox was profound; its rapid spread and severe symptoms led many indigenous people to believe their traditional gods had abandoned them.
Evolution of the Smallpox Virus
The viral genomes recovered from the mummies provided valuable insights into the evolution of the smallpox pathogen. The genomes were nearly identical, indicating that the two individuals were likely infected during the same outbreak. The researchers observed that the virus underwent a prolonged period of genetic evolution until the 16th century, after which its evolution slowed during the major epidemics associated with Spanish colonization. This pattern shifted again following the introduction of the first vaccine in 1796.
The findings suggest that the smallpox virus reached an evolutionary balance that allowed it to spread efficiently through populations lacking immunity, requiring minimal adaptation. The last naturally occurring case of smallpox was recorded in Somalia in 1977, and in 1980, the World Health Organization declared it the first and only human infectious disease to be eradicated globally.
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Published on 2026-07-31 00:43:00 • By the Editorial Desk
