Sign up for the Live Science daily newsletter now Get the world’s most fascinating discoveries delivered straight to your inbox. That means the variola virus found in the mummies is an evolutionary step between medieval European strains and modern strains, proving that Europeans brought smallpox to the Americas. The researchers hope that more samples of ancient variola virus are found throughout the Americas, to complete the picture of smallpox's evolution and movement. Studies have suggested Mpox might behave similarly to the historical variola virus, in that it seems to mutate to adapt to human hosts. "It's always useful to study ancient pathogens," Stone said, "helping us learn how these pathogens adapt to us."