Why you should care
The flea-bitten past could deepen our understanding of Darwin — and of how diseases spread.
Medieval life may not have been as bad as you thought. It turns out, the Black Plague that swept across Europe during the Middle Ages might have actually been good for human evolution. And it could hold some lessons about genetics, modern sanitation and the future of fighting disease.
Professor Sharon Dewitte, a biological anthropologist, learned all that from a bunch of old bones, according to her new study. The Black Death of the 1340s–1350s claimed some 25 million lives across the continent, says National Geographic. Imagine commercial ghost ships coming into port with the entire crew dead from disease, and entire towns wiped out.
It wasn’t the plague’s first time around: What scientists would later know as Yersinia pestis had also struck centuries before, wiping out a full half of Europe’s population in the 700s. The biggest cause for the plague’s spread: bites from fleas carried by rats.
At best, variants of the disease killed only half of those it attacked. At worst, in that pre-penicillin era, everyone died, Nat Geo reports. But there’s the bright spot amid the dark days of the Black Death…
But as millions died horrible, agonizing, puss-filled deaths, other survived. And those survivors lived into their 70s and 80s — ages more typically associated with our modern era than with the time of Geoffrey Chaucer, The Decameron and the failing Mongol empire.
“I think people have an overly negative view of life in the medieval period,” Dewitte says. “It’s true that life expectancy was lower in the past — but that doesn’t mean that everyone died by the age of 40 in the medieval period.”
A teachable moment
The Black Death might serve as a prime example of Darwinian natural selection, she says. “The surviving population [may have] contained a higher proportion of people who had genetic variants that made them less susceptible.”
Or, she says, “the surviving population might have had a smaller pool of genes than existed before the Black Death,” leading to genetic drift: a radical change in the gene pool among a small population.
Not that we’d wish an apocalyptic, death-by-pustules plague on any person, city or country. But in a way, in the end, the Black Death may have made humanity stronger.
An unexpected silver lining, indeed.