Before the world as we know it today even existed, humans were already adapting to completely foreign environments and unexplored dangers.
Early humans migrated out of Africa but did not enter empty land; instead, they encountered other humans, including Neanderthals.
Over time, interactions with Neanderthals produced lasting results that we still see in human populations today.
That encounter became biological, but how is Neanderthal DNA contributing to the difficulty of eliminating viruses today?
How ancient DNA shaped our biology
When humans moved into Europe and Asia tens of thousands of years ago, they began interacted more closely with Neanderthals.
The interaction produced genetic material that remains present in modern-day populations.
Many people have some form of this inherited DNA in their bodies, and many individuals do so unknowingly.
Some of the genes that were passed down appeared to assist the body’s ability to adapt and to defend itself against new environmental challenges. However, those inherited traits also remained in existence over long periods of time.
They continued to contribute to the workings of the human body, generation after generation.
As this progressed, these traits gradually evolved into a permanent fixture in our biology.
An unusual trend emerged
Humans do not all respond equally well to viral infections.
Some people rapidly recover. Others appear to host infections for extended durations without displaying any obvious or visible signs of illness.
After comparing data more closely, trends began to form among those who handled long-lasting infections differently.
The differences were not large or immediately apparent at first.
However, over time, they began to connect to something much larger, much older, and much more deeply rooted.
Why does inherited ancient human DNA continue to influence how modern viruses behave today?
This is one example of how research from the Natural History Museum shows that the impact on human biology is larger and lasts longer than we once thought.
Why Neanderthal DNA is making some modern viruses harder to fight off
The cause of how these two events connect cannot be explained by looking at only one specific area or factor.
Not all viruses act in the same way. Some progress quickly and then disappear within a short period, while others remain in the body for extended periods and, in some cases, for a person’s entire life.
These distinctions matter far more than they initially appear and have a much deeper impact on how the body responds to infections over time.
They create conditions in which the immune system has to react in very different and often unpredictable ways.
These differences are not always visible at first, but they begin to shape how effectively the body responds over time.
This means the body cannot respond in one consistent pattern across all infections, and the effects continue to build gradually.
The difference becomes evident over time
Some of the DNA inherited from Neanderthals responds differently depending on the type of virus it interacts with.
These variants are linked to higher levels of infections remaining in the body over longer periods.
The individual’s body continues to battle them; however, it may not be able to control them entirely or suppress them completely.
This does not imply that the effects of ancient DNA are solely negative.
Rather, it produces different outcomes depending on the surrounding conditions. What could serve a positive function in one scenario could alter the balance in another.
This process continues to evolve based on how long an infection lasts and how effectively the body is able to respond.
These changes do not happen suddenly but develop gradually as the immune system continues to interact with these long-lasting infections.
If something from tens of thousands of years ago still affects how viruses behave today, what else from our past is shaping our health?