The Black Death’s genetic legacy

This exercise is a part of Educator Guide: Plague Immunity Left a Lasting Mark / View Guide

Directions for teachers: Ask students to read the online Science News article “Black Death immunity came at a cost to modern-day health” and answer the following questions. A version of the article, “Plague immunity left a lasting mark,” appears in the November 19, 2022 issue of Science News.

1. What is bubonic plague? What germ causes this plague?

Bubonic plague is a highly infectious and deadly infection caused by the bacterium Yersinia pestis

2. What was the Black Death? How was it related to bubonic plague?

The Black Death was a wave of bubonic plague that lasted from 1346 to 1350 and wiped out roughly a third of the human population in Europe.

3. What gene did researchers in the article study? In what bodily system does the gene play a role?

Researchers studied the gene ERAP2, which plays a role in the human immune system.

4. What do the researchers claim about the gene and its relationship to the Black Death?

Researchers claim that having a specific version of the gene improved the odds of surviving the Black Death by as much as 40 percent.

5. What evidence do the researchers use to support their claim? Explain how the researchers gathered their evidence.

Researchers compared the genetic information of people who died before, during and after the Black Death and found that the frequency of this variant drastically increased in the population after the Black Death. In follow-up experiments with human immune cells, cells from people that have the variant and that were infected with Y. pestis fought off the bacteria better than cells from people without the variant.

6. Why did the frequency of the gene variant increase after the Black Death?

People with the variant had better odds of surviving the Black Death and passing on their genes than people without the variant. Therefore, more people with the variant survived and passed on the variant, than people without the variant.

7.  What implications does the gene variant have for modern-day health?

The variant has been linked with an increased risk of developing Crohn’s disease.

8. What broader hypothesis does the new finding support?

It supports a hypothesis that genetic changes that helped our ancestors better fight off ancient infections can have costs for people’s health today.