We carry DNA from extinct cousins like Neanderthals. Science is now revealing their genetic legacy

Our inner Neanderthals are still here.

Our early Homo sapiens ancestors coexisted with these distant cousins of ours, as well as other species known as Denisovans. As they socialized, they had kids. It's in our DNA, so part of who they were never really disappeared. And the extent to which that shapes us is beginning to be shown by science.

Scientists are discovering that characteristics passed down from our ancient cousins still exist in us today. These features impact our immune systems, fertility, and even how our bodies responded to the COVID-19 virus. This is made possible by the new and quickly developing capacity to put together bits of ancient DNA.

"We're now carrying the genetic legacies and learning about what that means for our bodies and our health," told the Rice University archaeologist Mary Prendergast.

Researchers have discovered connections between Neanderthal DNA and a severe hand ailment, nasal morphology, and other human characteristics just in the last few months. In order to study the gene's biological consequences, scientists even introduced a gene carried by Neanderthals and Denisovans into mice, discovering that it gave the animals bigger heads and an additional rib.

There is still much to learn about the human experience. However, according to Dr. Hugo Zeberg of the Karolinska Institute in Sweden, fresh research, partnerships, and technological advancements are assisting scientists in starting to address the fundamental but cosmic questions: "Who are we? From where did we originate?"

Furthermore, the responses reveal a startling truth: Despite our best efforts, we share a great deal more traits with our extinct relatives.


Up until recently, scientists could only deduce information about the size and shape of bones, which meant that the genetic heritage of prehistoric humans remained hidden. However, there has been a constant flow of new findings derived from ancient DNA, a field of research made possible by Nobel laureate Svante Paabo, who was the first to piece together a Neanderthal genome.

Scientists have been able to see things like genetic changes through time to better adapt to settings or via chance because to advancements in the discovery and interpretation of ancient DNA.

Even the amount of genetic material that individuals from various places share with our ancestors' old cousins may be determined.

Neanderthal DNA is found in 1% to 2% of groups from European and Asian ancestries, but virtually nonexistent in some African populations, according to research. In most areas of the world, Denisovan DNA is hardly noticeable; nevertheless, it accounts for 4% to 6% of the DNA of individuals living in Melanesia, which stretches from New Guinea to the Fiji Islands.

Even if it doesn't seem like much, it adds up. Zeberg, who works closely with Paabo, stated that "Half of the Neanderthal genome is still around, in small pieces scattered around modern humans."

It's also sufficient to have a very real impact on us. Although the entire extent is yet unknown, scientists are discovering that it can have both positive and negative effects.

Neanderthal DNA, for instance, has been connected to autoimmune conditions including rheumatoid arthritis and Graves' disease. Homo sapiens did not have immunity to illnesses found in Europe and Asia when they left Africa, but Neanderthals and Denisovans who were already residing there had.

"We got a quick fix to our immune systems by interbreeding with them, which was good news 50,000 years ago," said Chris Stringer, a specialist on human evolution at the Natural History Museum in London. As a result, some people now claim that their immune systems are hypersensitive and occasionally go into self-destruct mode.

A gene linked to blood clotting that is thought to have originated from Neanderthals in Eurasia would have also been useful in the "rough and tumble world of the Pleistocene," according to Rick Potts, the director of the Smithsonian Institution's human origins department. But as of right now, it can increase an older adult's risk of stroke. He declared, "There are costs in evolution for every benefit."

Zeberg and Paabo's 2020 study discovered that a significant genetic risk factor for severe COVID-19 is inherited from Neanderthals. "It was a perfect match when we compared it to the Neanderthal genome," Zeberg stated. "I almost toppled over in my chair."

The next year, researchers discovered that a group of DNA variations on a single chromosome that descended from Neanderthals had the reverse effect, shielding humans against severe COVID.

The list continues: Neanderthal genetic variations have been connected in studies to behavioral characteristics, skin and hair color, cranial form, and Type 2 diabetes. According to one study, those who report experiencing greater pain than others probably have Neanderthal pain receptors in their bodies. An other study discovered that one-third of European women have a Neanderthal progesterone receptor, linked to higher fertility and fewer miscarriages.

Much less is known about the Denisovan genetic heritage we carry with us, despite some studies connecting their genes to improved fat metabolism and altitude adaption. The University of Chicago's Maanasa Raghavan, a specialist in human genetics, reported that Tibetans, who still survive in low-oxygen conditions, had a portion of their Denisovan DNA.

Even within the genetic code of contemporary humans, scientists have uncovered evidence of "ghost populations"—groups whose remains have not yet been unearthed.


The story of modern humans' survival, according to Potts, "was always told as some success story, almost like a hero's story," in which humans triumphed against the "insufficiencies" of their cousins and ascended above the rest of nature.

"Well, that's just not the right story at all."

When Homo sapiens departed Africa, Neanderthals and Denisovans had already been there for thousands of years. It was formerly believed by scientists that our greater technology and more complicated behavior was the reason we prevailed. However, new findings indicate that Neanderthals were able to communicate, used fire for cooking, created art, used complex tools, hunted, and even wore jewelry and cosmetics.

Many ideas now link our capacity for long-distance travel to our ability to survive.

Zeberg declared, "We spread all over the world, much more than these other forms did."

Potts noted that whereas Neanderthals had evolved specifically for cold environments, Homo sapiens, having originated in tropical Africa, were able to spread to any type of climate. He declared, "We are so culturally and geographically adaptive to so many places in the world."

Eleanor Scerri, an archaeologist at Germany's Max Planck Institute for Geoanthropology, stated that Neanderthals and Denisovans likely found themselves stuck in tiny places due to severe circumstances including recurring ice ages and ice sheets. They were more vulnerable to genetic collapse since they were in smaller numbers.

We also possessed agile, productive bodies, according to Prendergast. Neanderthals had greater difficulty surviving and moving around than modern humans since it takes a lot more energy to support the stocky animals than it does for the relatively slender humans. This was especially true when food became limited.

The Canadian Museum of History's Janet Young, the curator of physical anthropology, brought attention to another fascinating theory that anthropologist Pat Shipman mentioned in one of her books: that dogs were crucial to human survival. The skulls of domesticated dogs were discovered by researchers in Homo sapiens sites at a considerably earlier epoch than previously known. Scientists think that dogs simplified hunting.

All other species of hominins on Earth had vanished by 30,000 years ago, leaving just Homo sapiens as the surviving species.


Nevertheless, each new scientific finding emphasizes how much we still owe our prehistoric relatives.

According to University of Wisconsin-Madison paleoanthropologist John Hawks, "survival of the fittest and extinction" was not the guiding principle of human evolution. It is concerned with "interaction and mixture."

With scientific advancements enabling them to extract information from ever-tinier remains of ancient life, researchers anticipate learning more. Modern scientists are able to extract DNA from the soil and silt that previously supported prehistoric humans, even in the absence of remains.

Additionally, they aim to study more in less-traveled parts of the globe. Zeberg stated that it is expected that additional nations would develop "biobanks" that gather biological samples.

Scientists anticipate to uncover much more evidence of our genetic heritage as they continue to explore how much of our ancient cousins influenced us.

Zeberg remarked, "Maybe we shouldn't see them as so different."