- Modern humans have small amounts of Neanderthal DNA, and these genes still influence our health today.
- Scientists think they have figured out when the two groups started interbreeding and exchanging DNA.
- The results may help scientists understand how Neanderthal genes evolved in humans over millennia.
We might think of Neanderthals as ancient and unrecognizable relatives, but humans once had very intimate relationships with them.
For example, our ancestors had children with shorter, stockier species and exchanged DNA for thousands of years.
Now scientists think they’ve figured out when much of this interspecies interbreeding occurred, which could provide clues as to why humans survived their ancient cousins.
By studying genomic data from both ancient and modern humans, scientists found that Neanderthals and humans had sex about 47,000 years ago, then stopped less than 7,000 years later—relatively short in evolutionary terms.
“This study gives us the most accurate picture yet of how some Neanderthals entered the modern human gene pool and what happened to their genes afterward,” said John Hawks, an anthropologist at the University of Wisconsin-Madison who was not involved in the research. , told Business Insider.
All humans have at least some Neanderthal DNA, a 2020 study found. These genes can influence everything from metabolism to our risk of diabetes.
Figuring out when humans acquired them can help scientists understand how these genes evolved and why they might have benefited our ancestors and stuck in our DNA for millennia.
When did humans and Neanderthals start interbreeding?
The basic story of human-Neanderthal relationships goes like this: We shared a common ancestor more than 500,000 years ago, then went our separate ways.
Then, about 75,000 years ago Neanderthals lived in Asia and Europe when some people began to migrate out of Africa. The two groups started having children together shortly after, sometime between 60,000 and 50,000 years ago.
But 40,000 years ago the Neanderthals became extinct.
For this latest study, scientists from the Max Planck Institute for Evolutionary Anthropology and the University of California, Berkeley examined the DNA of 59 people who lived between 45,000 and 2,200 years ago.
To find out when our ancient human ancestors linked to Neanderthals, the researchers compared stretches of Neanderthal DNA in their genomes. Individuals from about 40,000 years ago had long stretches of chromosomes containing genes that matched other species.
The researchers saw that after only a few thousand years, these segments became shorter. That means these people were more distantly related to Neanderthals, Hawks said.
Using computer software, the researchers created models to estimate how many generations had passed since a Neanderthal entered their family tree. from that they put the initial date of contact between humans and Neanderthals at about 47,124 years and estimated that interbreeding took about 6,832 years.
“The conclusion is quite strong,” Hawks said, because the estimates match both the earlier and later human genomes.
Neanderthals who live within us
Except ancient man DNA scientists also studied the genomes of 275 modern humans from different environments to learn more about how humans and Neanderthal genes has evolved for millennia.
“It is possible to trace the fate of individual parts of the chromosomes that were once in a Neanderthal individual, got into the modern descendants of that individual and were passed down to the present day,” Hawks said.
For example, scientists have found that both modern and ancient humans have Neanderthal genes that affect metabolism, immunity and skin pigmentation.
They speculate that these traits may have benefited ancient humans who inherited them and then passed them on. One hypothesis is that paler skin would help boost vitamin D levels in a gloomier climate.
Other studies link Neanderthal genes to autoimmune diseases and diabetes. On the other hand, some DNA from this species appears to protect humans from West Nile, hepatitis C, and SARS.
The results of the study may not apply to everyone. For example, no present-day humans of African descent were included, as only about 0.5% of their DNA comes from Neanderthals.
However, almost everyone else in the world is about 2% Neanderthal, so learning more about the genes of this species could shed light on the susceptibility of many people to certain diseases.
The researchers published their work in a preprint study that has not yet been peer-reviewed.