The Black Death of 1349 had a profound impact on Europe. According to a recent study, it would have left surprisingly few traces on the genetic heritage of the inhabitants of Cambridge. Contrary to previous research, the genetic aftereffects of this devastating epidemic seem less marked than previously thought, calling into question the understanding of the impact of major pandemics on human evolution.
The Black Death severely affected the city of Cambridge in England in 1349, causing massive mortality. The population could no longer even bury their dead and collective graves were commonplace. A recent study published in Science Advances surprisingly reveals that this tragic episode would not have left a significant mark on the genetic heritage of the (surviving) inhabitants of Cambridge. This conclusion goes against a 2022 study, which highlighted the enrichment of certain immune gene variants in survivors, suggesting a possible protective effect.
Epidemics and genome modifications
Bubonic plague is often associated with lasting changes to the human genome. Historically, certain genetic variants have contributed to survival against infections in various populations. However, it is complex to attribute these genetic changes to epidemicsepidemics specific as the Black Death, because the natural selectionnatural selection operates over many generations and the data genomicsgenomics old ones are often limited.
A landmark 2022 study analyzed hundreds of ancient genomes, identifying changes in the frequency of more than 200 immune gene variants after the Black Death. These changes were thought to help immune cells fight the pathogenicpathogenic responsible for the plague.
The particular case of Cambridge
To explore this hypothesis in other regions, researchers at the University of Cambridge sequenced the genomes of medieval Cambridge residents and residents of Cambridge from periods after the Middle Ages. However, their analysis revealed only a slight change in the frequency of certain variants, with no clear signs of natural selection linked to the Black Death. Even a specific variant, linked to resistanceresistance against plague, showed no significant variation.
Separately, the researchers highlighted potential flaws in the 2022 study, calling into question the validity of established associations between genetic variants and the Black Death. Despite this, some scientists continue to support the existence of genetic selection linked to past epidemics, while admitting that much larger genome samples would be needed to confirm these hypotheses.
In conclusion, although repeated pandemics can influence the evolution of the human genome, the specific impact of a single epidemic, such as the Black Death, on genetic changes remains a matter of debate. Further research and broader genomic data will be needed to clarify these questions.
