16th century skeletons suggest the slave trade brought some diseases to Mexico

The remains of slaves buried in a mass grave carried hepatitis B and yaws

Three skeletons excavated in Mexico City, including these skulls, came from African slaves who carried versions of two infectious diseases that were novel to the Americas in the 1500s, a new study finds.

R. Barquera et al/Current Biology 2020

Slavery proved contagious when Spain colonized 16th century Mexico. Africans abducted into the transatlantic slave trade and taken to Mexico around that time may have introduced forms of two infectious diseases, hepatitis B and yaws, to the Americas, researchers say.

DNA of three men whose skeletons were previously excavated near a Mexico City hospital indicates that all were from western or southern Africa, say archaeogeneticist Rodrigo Barquera of the Max Planck Institute for the Science of Human History in Jena, Germany, and his colleagues. The men’s upper front teeth had been filed down, a practice known to have characterized African slaves in the Americas, the scientists report online April 30 in Current Biology.

Forms of strontium, carbon and nitrogen in the men’s teeth, which indicate the region where a person grew up, also suggest childhood origins outside Mexico.

One man’s tooth carried DNA from a strain of the hepatitis B virus (SN: 4/30/13) typically found in present-day West Africans, the investigators say. While it’s unclear when hepatitis B infections first occurred in the Americas, the researchers contend that African slaves brought a novel genetic form of hepatitis B to Mexico.

Another man’s tooth yielded bacterial DNA from a yaws strain also observed in modern West Africans. Yaws is a painful infection of the bones, joints and skin (SN: 5/21/19). Previous research found a closely related West African yaws strain in the skeleton of a 17th century individual with European ancestry who was buried in Mexico City, suggesting that yaws carried by African slaves around a century earlier continued to infect people in the region.

The three men lived sometime between 1436 and 1626, based on radiocarbon dates of their teeth. They are the oldest genetically identified first-generation Africans in the Americas. As slaves, the men likely reached Mexico in a transatlantic bondage system Spain started in the early 1500s, the scientists suspect.

These individuals died in their 20s before being placed in a mass grave, Barquera’s team estimates. The men’s bones display evidence of hard labor, including signs of carrying heavy loads, injuries such as leg fractures and damage from malnutrition or parasitic infections. 

Bruce Bower has written about the behavioral sciences for Science News since 1984. He writes about psychology, anthropology, archaeology and mental health issues.

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