Ancient endemism

Smallpox is a very ancient disease that has been mentioned in medical writing dating back to the third century AD. It originated in Egypt or India and became endemic in both of these countries. In the seventeenth and eighteenth centuries, it is estimated to have killed almost half a million people every year in Europe. The Spanish conquerors (conquistadors) of Mexico and Peru took smallpox with them. It is estimated to have killed over three million Aztec Indians, who had no immunity against this disease because, until then, it was unknown in the New World. 

Hadley, E. A., van Tuinen, M., Chan, Y., and Heiman, K. (2003) Ancient DNA evidence of prolonged population persistence with negligible genetic diversity in an endemic tuco-tuco (Ctenomys sociabilis). Journal of Mammalogy, 84 403 17. 

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