Recent studies suggest that Neanderthal DNA may still be influencing immune responses in people of European descent, creating distinct differences between populations.
This genetic legacy could explain why some individuals are more prone to certain autoimmune diseases, while others have stronger defenses against infections.
A groundbreaking study has revealed that people of African and European ancestry have strikingly different immune responses—differences that may be traced back to interbreeding between early modern humans and Neanderthals tens of thousands of years ago.
Researchers found that individuals of African descent exhibit a more aggressive immune response, a double-edged sword that helps fight infections more effectively but also increases susceptibility to autoimmune diseases.
Meanwhile, Europeans seem to have inherited a dampened immune response, likely due to their ancestors’ interactions with Neanderthals.
The Study That Revealed an Ancient Divide
A team of researchers led by geneticist Luis Barreiro at the University of Montreal set out to investigate how immune responses vary between populations.
They studied blood samples from 175 Americans, with roughly half of the participants being of African ancestry and the other half of European descent.
To test immune function, scientists extracted macrophages—specialized immune cells that engulf and destroy harmful bacteria.
These cells were then exposed to two common pathogens: Listeria and Salmonella.
After just 24 hours, a remarkable difference emerged: macrophages from individuals of African descent were three times more effective at eliminating bacteria compared to those from individuals of European ancestry.
This heightened inflammatory response is beneficial for fending off infections, but it comes with a tradeoff.
Excessive inflammation is a known risk factor for autoimmune diseases, including conditions like Crohn’s disease and rheumatoid arthritis.
According to Barreiro, this means that while African-descended individuals may have an advantage in fighting infections, they are also at greater risk for diseases where the immune system attacks the body’s own cells.
Did Neanderthals Play a Role?
For decades, scientists have known that modern Europeans inherited about 1-2% of their DNA from Neanderthals, but only recently have researchers begun to uncover how those genes impact health.
One of the most surprising discoveries is that Neanderthal genes appear to have influenced immune system regulation.
Barreiro’s team found evidence that macrophages from individuals of European descent carried traces of Neanderthal DNA, which affected how their immune cells responded to infections.
Unlike the highly inflammatory immune response seen in African samples, European macrophages displayed a more controlled, less aggressive reaction.
But why would a dampened immune response be beneficial? One theory is that early humans who migrated to Europe encountered fewer deadly pathogens compared to their African ancestors.
In this new environment, a hyperactive immune system may have been more harmful than helpful, leading to chronic inflammation and increased susceptibility to autoimmune diseases.
The interbreeding between Neanderthals and early modern humans may have introduced genetic variations that helped regulate the immune response, reducing unnecessary inflammation.
A Second Study Confirms the Findings
Another study, led by Lluis Quintana-Murci at the Institut Pasteur in France, examined the immune responses of 200 individuals—half of African descent and half of European ancestry.
Instead of focusing on macrophages, this research looked at monocytes, another type of immune cell responsible for fighting infections.
The team exposed these monocytes to bacterial and viral molecules, including the influenza virus, and once again observed a clear pattern: the immune response in European participants was characterized by reduced inflammation compared to the African group.
The study further confirmed that Neanderthal genes played a role in shaping these differences.
Quintana-Murci explains, “Reducing immune inflammatory responses is a way to avoid autoimmunity, inflammatory, and allergic reactions.
Finding that reduced immune responses conferred an advantage highlights the tradeoff between recognizing pathogens while avoiding excessive immune reactions.”
Challenging Common Assumptions About Immunity
For years, many believed that a stronger immune system was always better.
But these findings suggest that there’s no single “best” immune system—only one that is better suited for specific environments.
The assumption that European immune systems are weaker isn’t entirely accurate.
Rather, their immune response has been optimized for a different set of challenges.
While individuals of African ancestry excel at fighting infections, they face a higher risk of inflammatory diseases.
Europeans, on the other hand, have a more balanced immune response, but that comes at the cost of being more susceptible to infections.
This idea aligns with what evolutionary biologists call the hygiene hypothesis—the notion that people who live in cleaner environments with fewer pathogens tend to develop weaker immune responses over generations.
The Neanderthal-influenced immune system of Europeans may be a direct result of this kind of adaptation.
Why This Matters for Modern Medicine
The implications of these studies extend beyond academic interest.
Understanding how genetic ancestry influences immune responses could lead to breakthroughs in personalized medicine.
Imagine a future where doctors can tailor treatments based on a patient’s genetic background, optimizing therapies for immune disorders, autoimmune diseases, and even vaccine effectiveness.
Furthermore, these findings highlight the need for greater diversity in medical research.
Many studies focus primarily on European populations, meaning that medical treatments and drug responses may not be equally effective for people of African descent or other ancestries.
Expanding research to include diverse genetic backgrounds will help develop better, more inclusive healthcare solutions.
The Next Steps in Immune Research
Despite these breakthroughs, researchers acknowledge that genetics only explains about 30% of the observed immune differences.
That means other factors—such as environment, diet, and lifestyle—also play a significant role.
“There is still much to do,” says Barreiro. “Our future studies should focus on other factors, emphasizing the influence of the environment and our behavior.”
Future research will likely explore how modern lifestyle changes, urbanization, and even gut microbiomes influence immune function.
By piecing together the complex interactions between genetics and environment, scientists hope to unlock new ways to treat immune-related diseases and improve human health.
A Legacy Written in Our DNA
The immune system is not just a product of biology—it is a living record of human history.
The struggles of our ancestors, the environments they adapted to, and even their interactions with other species have left permanent marks on our DNA.
The fact that Neanderthal DNA still plays a role in human immunity today is a stunning reminder that evolution is ongoing.
As we continue to uncover the secrets of our genetic past, we may also be paving the way for a future where medicine is truly personalized, tailored to our unique biological heritage.
