Smallpox DNA Discovered in 16th-Century Chilean Mummies

Researchers have recovered ancient viral DNA from South American mummies, providing the first direct molecular evidence of the smallpox pathogen brought from the Old World during the Spanish colonization, according to a study published on Thursday in the journal Science.

Smallpox DNA Recovered from Chilean Mummies

According to geneticists at Trinity College Dublin, the ancient viral DNA was extracted from the mummified remains of two individuals who died during the early Spanish colonial period in an Inca community in northern Chile. Analysis of the variola virus genomes showed they belonged to a now-extinct lineage situated evolutionarily between medieval European strains and those circulating in later centuries, as reported by lead study author Bruno Romero González.

Impact of Disease on Indigenous Populations

When Europeans arrived in the Americas in 1492, indigenous populations lacked previous exposure to smallpox and had no natural immunity. According to Trinity College Dublin geneticist and study co-author Shigeki Nakagome, the pathogen triggered a cataclysmic population collapse, killing an estimated 90% of indigenous people in the Americas and helping the Spanish vanquish the Aztec, Maya, and Inca empires.

Natural Mummification at Camarones Cove

The two individuals lived in the southern reaches of the former Inca Empire at a site close to the Pacific coast near Camarones Cove in Chile, according to Universidad de Chile biological anthropologist and study co-author Constanza de la Fuente Castro. The bodies belonged to a woman aged 30 to 35 and a man aged 18 to 20. Both were naturally mummified, wrapped in camelid wool blankets, and buried in bundles with grave goods rather than being chemically altered like Egyptian mummies.

Viral Evolution and Historical Context

Genomic analysis revealed that the two viral samples were almost identical, indicating the victims were infected during the same outbreak or by the same circulating strain. Researchers found that the pathogen’s genetic evolution decelerated during the major smallpox epidemics of the Spanish colonization, suggesting the virus had achieved an evolutionary optimum that allowed it to spread efficiently without further adaptation through populations lacking immunity.

Frequently Asked Questions

What caused the smallpox outbreak in the Americas?

Smallpox was carried from the Old World to the New World by Spanish conquistadors and settlers, transmitting the variola virus through person-to-person contact among indigenous populations who had no natural immunity.

How was the ancient smallpox DNA discovered?

Researchers extracted ancient viral DNA from the naturally mummified remains of two individuals buried in an Inca community in northern Chile during the early Spanish colonial period, according to findings published in the journal Science.

When was smallpox officially eradicated?

The last naturally occurring smallpox case was recorded in Somalia in 1977, and the World Health Organization declared the disease eradicated worldwide in 1980 after a global vaccination campaign.