Is There a Benefit to Having Neanderthal DNA in the Human Genome?
Most people are made up of between 1 and 4 percent Neanderthal DNA, depending on what part of the world you call home, according to the National Institutes of Health (NIH).
For those who live in Africa or are of African descent, their percentage of Neanderthal DNA is the lowest, while those in East Asia have been shown to have the highest percentage, according to a study published in Genetics.
So how did the DNA of an archaic human who went extinct 40,000 years ago end up in our genome and are there any benefits?
Read More: Everyone Has Neanderthal DNA in Their Genome, New Genetic Analysis Shows
Why Do Modern Humans Still Have Neanderthal DNA?
According to John Anthony Capra, an evolutionary genomics professor at the University of California, San Francisco, modern humans and Neanderthals got together when modern humans moved out of Africa around 40,000 years ago and into Neanderthal territory in Europe and Asia.
“Neanderthals were a group that had broken off from the lineage that would ultimately become us about [500,000] to 700,000 years ago, and they lived across broad ranges in Europe, Asia, and the Middle East for hundreds of thousands of years before our more immediate ancestors moved into those environments,” says Capra.
But once they came into contact, they interacted and were genetically close enough that they could interbreed and have children that would then carry Neanderthal DNA. All these years later, we still carry an imprint of Neanderthals in our genome.
Individuals of African descent have very little Neanderthal DNA because they never left the continent, so they never came into contact with these archaic humans. But the average person living outside of Africa still has an average of 2 percent Neanderthal DNA, says Capra.
This is also true of another group of archaic humans called Denisovans, which still appears prominently in the DNA of Oceania and Southeast Asia populations. This group of archaic humans, which is more genetically similar to Neanderthals than it is to modern humans, came along around 370,000 years ago, according to Britannica.
How Did We Interact With Neanderthals?
According to the Human Origins Initiative, if you saw a Neanderthal walking down the street, you would know they were very different, but it wouldn’t have stopped you from getting together. We don’t know for sure how often modern humans interbred with Neanderthals, but we do know that it happened commonly because they likely overlapped for many years before Neanderthals went extinct.
Neanderthal specimens that have been sequenced also contain remnants of modern human DNA, suggesting some regularity.
“These kind of interbreeding events were not rare,” says Capra.
It may be hard to imagine now, but just before that, around 100,000 years ago, the world would have been populated by many groups of human-like ancestors who were not the same as us but interbred with one another. At that time, depending on where you were living in the world, you could encounter Homo sapiens, Homo neanderthalensis, Homo erectus, Homo floresiensis, or Denisovans, according to the Australian Museum.
Neanderthal DNA Found in the Genome
Certain aspects of the Neanderthal genome have remained because they’re beneficial. Others are gone because, well, you guessed it, they’re not.
“Many of the parts of our genome that encode genes expressed in the brain are very strongly depleted for Neanderthal ancestry,” says Capra.
This means our brains are very different from those of Neanderthals, and this was likely true when the two groups interbred. The hybrids that would have resulted were less likely to thrive and carry on their traits over generations.
On the other hand, there are certain parts of the genome tied to the immune system that are more likely to include Neanderthal DNA. This is related to the fact that, when modern humans left Africa, they would have needed to adapt to pathogens found in Europe and Asia.
Many experts contend that modern humans and Neanderthal tribes commonly lived together, which would support one theory of how Neanderthals went extinct, according to a July 2024 study published in the journal Science. Basically, instead of actually going extinct, perhaps the DNA of modern humans simply subsumed that of Neanderthals because those features were the most successful.
Read More: How Much Neanderthal DNA do Humans Have?
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