Black Death Survivors and Their Descendants Went On to Live Longer

The plague preferentially killed the very old and those already in poor health. Natural selection or better diets may have allowed those who remained to thrive

A depiction of the black death from a 15th-century Bible

The Black Death, a plague that first devastated Europe in the 1300s, had a silver lining. After the ravages of the disease, surviving Europeans lived longer, a new study finds.

An analysis of bones in London cemeteries from before and after the plague reveals that people had a lower risk of dying at any age after the first plague outbreak compared with before. In the centuries before the Black Death, about 10 percent of people lived past age 70, said study researcher Sharon DeWitte, a biological anthropologist at the University of South Carolina. In the centuries after, more than 20 percent of people lived past that age.

"It is definitely a signal of something very important happening with survivorship," DeWitte told Live Science. [Images: 14th-Century Black Death Graves]

The plague years

The Black Death, caused by the Yersinia pestis bacterium, first exploded in Europe between 1347 and 1351. The estimated number of deaths ranges from 75 million to 200 million, or between 30 percent and 50 percent of Europe's population. Sufferers developed hugely swollen lymph nodes, fevers and rashes, and vomited blood. The symptom that gave the disease its name was black spots on the skin where the flesh had died.

Scientists long believed that the Black Death killed indiscriminately. But DeWitte's previous research found the plague was like many sicknesses: It preferentially killed the very old and those already in poor health.

That discovery raised the question of whether the plague acted as a "force of selection, by targeting frail people," DeWitte said. If people's susceptibility to the plague was somehow genetic perhaps they had weaker immune systems, or other health problems with a genetic basis then those who survived might pass along stronger genes to their children, resulting in a hardier post-plague population.

In fact, research published in February in the journal Proceedings of the National Academy of Sciences suggested that the plague did write itself into human genomes: The descendants of plague-affected populations share certain changes in some immune genes.

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Black Death Survivors and Their Descendants Went On to Live Longer