Ancient DNA reveals genetic legacy of pandemics in the Americas

Tuberculosis, treponemal disease, Chagas disease, and many other pathogens were endemic to populations of Prehistoric America. But the "Columbian Exchange" beginning in 1492 introduced new pathogens to American populations, including smallpox, measles, influenza, and yellow fever.

This introduction had devastating consequences for tribes. Infectious diseases resulted in the depopulation of complete regions, leading to the collapse of social, economic, and political institutions, and the loss of many traditional cultural practices and ways of life.

The dynamics of these pandemics is critical to learn how they have shaped the genetic diversity of contemporary Native American communities, giving insights into the genetic foundations of diseases present in a higher frequency in some populations than elsewhere.

Documenting the historical effects of the introduction of novel pathogens can give insights into the evolution of host-pathogen relationships, useful for responding to future outbreaks of emerging infectious diseases, The Guardian has reported.

Hypotheses have suggested that years of separation and independent evolution from Old World populations rendered the indigenous inhabitants of the Americas immunologically susceptible to the pathogens.

The resulting outbreaks of disease - the so-called "virgin soil epidemics" - following first exposure to these pathogens were, thus, devastating. But many of these diseases leave no trace of infection in skeletons, making it impossible to fully test this model using only osteological approaches.

However, our ability to recover DNA from past populations gives us a way to document the evolutionary effects of these pandemics.