AP Biology class blog for discussing current research in Biology

Tag: #Black Death

Would You Have Survived the Black Death?!?!

New research from McMaster University, the University of Chicago, the Pasteur Institute, and other organizations suggests that during the Black Death, 700 years ago, there were select individuals whose genes actually PROTECTED them from the devastating population-crushing Bubonic Plague.

Model of bubonic plague bacteria - Smithsonian Museum of Natural History - 2012-05-17

The Bubonic Plague, later nicknamed the Black Death after many realised people would develop blackened tissue on their body postmortem, due gangrene(the death of tissue due to lack of blood flow). “It remains the single greatest human mortality event in recorded history, killing upwards of 50 per cent of the people in what were then some of the most densely populated parts of the world.” (

The team researching this genetic phenomena collected DNA from the deceased 100 years before, during and after the Black Death. They collected samples from the greater London area, as well as some parts of Denmark to accurately represent Upon searching for evidence of genetic adaptation, they found 4 different genes prevalent in the pandemic survivors, all of which are protein-making genes that are used in our immune systems, and found that versions of those genes, called alleles, either protected or rendered one susceptible to plague. We in AP Biology will soon learn more about alleles in higher depth, for they are imperative in the genetics of almost every DNA-carrying organism’s survival.

People with two identical copies of a gene named ERAP2 were able to survive the Black Plague at significantly higher rates than those who lacked that specific gene. “When a pandemic of this nature …  occurs, there is bound to be selection for protective alleles in humans … Even a slight advantage means the difference between surviving or passing. Of course, those survivors who are of breeding age will pass on their genes”.- evolutionary geneticist Hendrik Poinar. Mr. Poinar’s analysis of this research poses a unique and interesting question. Does the natural selection that occurred during the Bubonic Plague mean that you and I have a higher chance of having this gene in our DNA? If another plague with a similar biological makeup to the Black Death, would our bodies be better suited to find it?

You Survived The Black Death… But At What Cost?


1346-1353 spread of the Black Death in Europe map

As we all know, the Black Death, which occurred from 1346 to 1352, is regarded as the deadliest plague in human history. It killed about a third of the Earth’s population and survivors were left with physical and emotional scars. However, one of the most wondered aspects of this pandemic was how so many people still managed to survive, since the plague came with a 30-60% chance of death. Today, though, we know that genetic variants in people at the time granted their bodies a stronger ability than others to fight off the disease or even avoid it. Those survivors, thanks to Charles Darwin’s evolutionary theory of survival of the fittest, were able to pass down those genetic variants; however, what is not commonly talked about is how these genetic variants currently affect the descendants of the Black Death survivors. 


Recently, it has been discovered that the same genetic mutations that saved civilians in the 14th century from the plague are now the same ones that are increasing civilians in the 21st century’s risk of disorders such as Crohn’s Disease. 


The two genetic variants most credited with providing protection against Yersinia pestis, the bacteria that causes the bubonic plague, are ERAP2 and NOD2. Both of these genes have been proven to assist the body and immune system in fighting off the infection faster, and have been passed down generation to generation thanks to the survivors of the plague. However, it has also been discovered that these genes are linked to Crohn’s Disease. Crohn’s Disease is an inflammatory bowel disease that causes swelling in the digestive tract, and a major risk factor of the disease is NOD2. It has also been recently suspected that ERAP2 is also causing individuals to be genetically predisposed to Crohn’s Disease. While ERAP2 does not increase a person’s chances of developing Crohn’s, it is still something to be concerned about, especially since NOD2 has already also been identified as a risk factor for several years. 


In conclusion, it is safe to say that while the Black Death may be over, the long term ramifications of it are most certainly not and there is still more information to be found as to how these ramifications present themselves today. 


How do you feel about these new findings surrounding the Black Death and the revelation that what could save someone from it hundreds of years ago could be the same thing that puts someone at risk to another disease today? 

One Generation’s Trash is Another Generation’s Treasure: How a selected mutation during the Black Death causes dangerous illness today

The Covid-19 pandemic has certainly changed millions of lives forever, but many scientists wonder how the pandemic could affect the human genome.  In a 2022 article in US news, researchers studied the Black Death, the 14th-century pandemic that wiped out nearly 25 million Europeans, and in particular, how it affected our bodies.

According to researchers, the Black Death led our bodies to select for certain genetic traits which at the time decreased their risk of infection.  These specific genes increased the activity of the immune system to better help fight the plague, however, today these mutations are having dangerous consequences.  Researchers have noticed a connection between such genes and the risk of numerous conditions, such as Crohn’s Disease, Lupus, and Rheumatoid Arthritis.  These illnesses are known as Autoimmune Diseases, a class of illnesses that occurs when the body tricks itself into attacking its own cells.

These specific genes increased the activity of the immune system to better help fight the plague, however, today these mutations are having dangerous consequences

According to LibreTexts, this phenomenon occurs when certain pathogens have a very similar molecular structure to the antigens that our bodies produce.  Therefore, our bodies are tricked into attacking their own cells thinking that they are pathogens.  This destroys important structures in our bodies, the absence of which causes illness, such as Crohn’s disease and Rheumatoid Arthritis.

According to Dutch biologist Henrik Poinar of McMaster University, “A hyperactive immune system may have been great in the past.” This hyperactivity may have led to an increase in activity against the plague, which in turn could have increased survival rates.  This groundbreaking research suggests that even the shortest event of monumental importance can forever change our bodies.  As stated by senior researcher Luis Bareirro, “Our genome today is a reflection of our whole evolutionary history.

The obvious question here is: will our current Covid-19 pandemic affect our bodies and are our bodies evolving? Researchers say no.  According to Barreiro, Covid’s low fatality rate makes it unlikely to cause any significant genetic change.   However, Covid’s mutations are difficult to predict, and we have no way of knowing how future mutations will affect our bodies.  Furthermore, in a recent study from Stanford Medical school, researchers identified 1,000 genes linked to severe Covid infection.  It is theoretically possible for these genes to be selected for as we evolve, and it is unclear how that could affect our ancestors.

Covid’s low fatality rate makes it unlikely to cause any significant genetic change

This selection is similar to the selection we are performing on fast-growing flowers in Biology class.  Like the removal of flowers without hairs, certain human genetic traits (probably not hairs) perform more favorably in a pandemic environment and may prevail due to natural selection.

While it is impossible to know what the future will hold, it is interesting to analyze how major historical events, like the Black Death, have affected our bodies.  While there isn’t consensus around how the current pandemic will affect our ancestors, scientists agree that these events are clearly linked to our evolution as a species.  According to Barreiro, “It’s not going to stop. It’s going to keep going for sure.”

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