At most, just 7% of the human genome is unique to our species. We share most genes with Neanderthals, Denisovans, and other ancestors.

Neanderthal
An employee of the Natural History Museum in London looks at model of a Neanderthal male in his twenties, which is on display at the museum’s “Britain: One Million Years of the Human Story” exhibition, September 2014.

Humans like to think they’re special, but our genes suggest that’s far from the case.

No more than 7% of the human genome is unique to Homo sapiens, according to a study published Friday in the journal Science Advances.

We share the remaining chunks of our genetic material with other human ancestors, or hominins, including our Neanderthal cousins and the Denisovans first discovered in east Asia.

“The evolutionary family tree shows there are regions of our genome that make us uniquely human,” Richard Green, director of the paleogenomics lab at the University of California, Santa Cruz and co-author of the new study, told Insider. “Now we have a catalog of those, and it’s a surprisingly small fraction of the genome.”

Anthropologists already knew that our hominin ancestors all interacted and interbred – exchanging genes and stone technologies that altered the course of our species’ evolution. But these new findings further underscore just how frequently that intermingling happened in the last 300,000 years or so, since the first known population of modern humans emerged.

“More or less everywhere we look, admixture is not the exception at all, but rather the rule,” Green said.

Genetic evidence suggests our ancestors interbred with mysterious hominins

Neanderthal family
An exhibit shows the life of a neanderthal family in a cave in the new Neanderthal Museum in the northern town of Krapina, Croatia, February 25, 2010.

To construct a hominin family tree, Green’s team sequenced and compared genomes from 279 modern humans – sampled from people all over the world – to ancient genomes from one Denisovan and two Neanderthals. Then, the researchers used a computer algorithm to determine out how each of those individuals are related to each other.

The analysis tool, which Green said took years to develop, helped them distinguish what parts of the human genome are devoid of admixture – meaning these sets of genes aren’t seen in Neanderthals or Denisovans.

The algorithm also highlighted what genes humans inherited from an even older ancestor, one that lived 500,000 years ago or so, that eventually gave rise to our species as well as Neanderthals and other hominins.

The study results suggest mysterious populations of human ancestors that scientists haven’t even discovered yet may have interbred with Neanderthals and Denisovans before these species mixed with modern humans, Green added.

Genes unique to humans are related to our brain development

denisovan mtDNA lab work
A scientist at work in a laboratory at the Max Planck Institute for Evolutionary Anthropology analyzing ancient DNA.

Researchers have already identified many of the human genes that resulted from cross-species trysts, but this is the first study to pinpoint what regions of genes were completely devoid of admixture, according to Green.

His group found these uniquely human regions of our genome were “incredibly enriched for genes that have to do with neural development,” Green said.

While Neanderthals have similarly large, if not larger, heads than humans do, that cranium size tells us little about how well their brains work compared to ours.

“Now we know human-specific stuff has to do with brain function,” Green said.

And most of these uniquely human genes came out during two distinct bursts of evolution – one that happened 600,000 years ago and another 200,000 years ago – the study found.

One of those evolutionary waves could’ve laid the genetic groundwork for human communication, Green said.

“It’s extremely tempting to speculate that one or more of these bursts had something to do the incredibly social behavior humans have – mediated in large part by our expert control of speech and language,” he said.

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3 species of human ancestors may have mixed and mingled in one Siberian cave 45,000 years ago – altering our evolution

denisova cave
The Denisova cave in Russia’s Anui River Valley.

Denisova Cave, high in the mountains of Siberia, was a happening place for our ancestors 300,000 years ago. Anthropologists have known that for a while: Scientists have excavated bones and teeth there from our Neanderthal and Denisovan cousins – and one of their hybrid children – over the last two decades. They’ve also found stone tools and jewelry.

But according to a recent study in the journal Nature, modern humans appear to have joined the party, too.

An analysis of ancient DNA culled from sediment on the cave floor suggests that these Homo sapiens occupied the cave starting around 45,000 years ago. So they may have overlapped with Neanderthals and Denisovans.

“We now have the first direct evidence for the presence of ancient modern humans at the site,” Elena Zavala, an evolutionary anthropologist at the Max Planck Institute in Germany and a co-author of the study, told Insider.

Neanderthal Evolution
An exhibit shows the life of a Neanderthal family at the Neanderthal Museum in the town of Krapina, Croatia, February 25, 2010.

The findings offer further insight into how our human ancestors interacted and interbred – exchanging genes and tool-making technology that altered the course of our species’ evolution.

“I cannot think of another site where three human species lived through time,” Katerina Douka, an archaeologist who was not involved in the study, told Science.

Ancient DNA tells a 300,000-year story

Zavala’s team collected more than 700 soil samples between 300,000 and 20,000 years old from across the cave’s three chambers.

One-quarter of those samples contained hominin DNA from microscopic bits of human skin, hair, and poop that got mixed into the sediment. The researchers also found DNA from ancient dogs, bears, hyenas, and horses.

denisovan mtDNA lab work
A scientist analyzes ancient DNA in a laboratory at the Max Planck Institute for Evolutionary Anthropology.

From their extensive DNA analysis, they were able to piece together a timeline of the cave’s occupants. Starting about 250,000 years ago, during a period of global warming, Denisovans started using the cave. Then roughly 60,000 years later, as the climate shifted and temperatures started to drop, Neanderthals arrived on scene.

The two hominins shared the cave for another 60,000 years before traces of the Denisovans disappeared from the fossil record.

For 30,000 years, Neanderthals were the cave’s sole occupants. After that, the new study reveals, a second population of Denisovans emerged. That happened about 100,000 years ago, at the start of the last global ice age. DNA evidence suggests both these Denisovans and their Neanderthal cave-mates survived for up to 78,000 years more.

That’s an important part of the timeline, according to the study, because it suggests those two hominin groups were still thriving in Denisova Cave when the first Homo sapiens showed up 45,000 years ago.

denisova cave
Layers of sediment on the walls of the Denisova Cave.

The team found DNA from all three species in a layer of soil that’s between 45,000 and 22,000 years old – which suggests they all overlapped.

A meeting point for hominins

denisovan
A portrait of a young female Denisovan based on a skeletal profile reconstructed from ancient DNA.

The fact that three hominin species all chose the same cave got Zavala thinking: What made this spot so special?

“It’s interesting that Denisovans and Neanderthals kept returning to the cave because it is located at the edge of what is thought to be each of their geographical ranges,” she said. (Neanderthals were predominantly from Europe, and Denisovans from Asia.)

Most likely, according to Zavala, it sat along a migration route between Europe and Asia.

“This cave was repeatedly meeting point between these two regions,” she said.

But to verify this idea, anthropologists would need to find more sites along this potential migratory path.

denisova cave
A view from the Denisova Cave in Russia.

Zavala thinks excavators will continue to find more traces of hominin and animal occupants in Denisova Cave.

Previously, anthropologists had to rely on fossils to assess which ancient species were present in an area. But pulling DNA straight from the soil has increased the amount of evidence scientists have to work with, thereby making findings like Zavala’s possible.

“We are not limited by the rare discovery of skeletal materials,” she said.

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‘Dragon Man,’ a mysterious new human species found in China, could be a closer relative of ours than Neanderthals

Homo longi dragon man
An artist’s concept of Homo longi, or “Dragon Man.”

About 146,000 years ago, a hunter died in the forests of what is now northern China. His skull remained almost perfectly preserved in sediment until bridge builders in Harbin found it in 1933.

At that time, Harbin was occupied by Japan, so a Chinese worker hid the skull in an abandoned well, where it remained for 85 years. The worker told his grandson about the hidden bone, now known as the Harbin cranium, and three years ago it finally made its way to anthropologists at the Hebei GEO University.

A trio of papers published Friday reveal that the skull belonged to a previously unknown species of human ancestor, called Homo longi.

“Because the Harbin fossil is so well preserved and informative, it is one of the most important finds so far for the last 500,000 years of human evolution,” Chris Stringer, an anthropologist at the Natural History Museum in London who co-authored the studies, told Insider.

Stringer’s team nicknamed this new hominin species “Dragon Man,” after the province where it was found: Heilongjiang, which translates to “dragon river.”

According to the new research, “Dragon Man” could be the closest known relative of modern humans – closer than Neanderthals, the group to which that title previously belonged.

‘Dragon Man’ might have interbred with ancient humans

Homo longi dragon man
Skulls of different human ancestors uncovered in China so far – the “Dragon Man” skull is on the far right.

According to the new studies, the Harbin cranium came from a 50-year-old male. The analysis also showed that Homo longi had a brain size comparable to that of modern humans, though parts of its skull resemble those of more ancient hominins.

As shown in the video below, Homo longi’s skull is massive and has a flatter shape, with square eye sockets, thick eyebrow ridges, and oversized teeth. These are characteristics more typical of Neanderthals, and they suggest that “Dragon Man” was relatively large. From the skull’s size, researchers think the species had adapted to survive in harsh environments.

“Like Homo sapiens, they hunted mammals and birds, and gathered fruits and vegetables, and perhaps even caught fish,” Xijun Ni, a paleoanthropologist at the Hebei GEO University who co-authored the studies, said in a release.

During the period 146,000 years ago, known as the Middle Pleistocene, various human ancestors crossed back and forth between Africa, Asia, and Europe. Modern humans were already living in western Asia, including the Arabian Peninsula, so in their eastern migration, they could have crossed paths with the “Dragon Man.”

“We don’t know if this population survived long enough to meet Homo sapiens, but they may well have done. If Neanderthals could interbreed with modern humans, then I’m sure that the Harbin group could too,” Stringer said.

Humanity’s closest relative?

Neanderthal
An employee of the Natural History Museum in London looks at model of a Neanderthal male in September 2014.

To determine whether Homo longi was more like Homo sapiens or Neanderthals, the researchers measured more than 600 parts of the Harbin skull, then compared the data to 95 other hominin skulls. A computer analysis revealed that “Dragon Man” was likely closer on the evolutionary tree to modern humans than to Neanderthals – meaning the species shared a more recent common ancestor with us.

“We found our long-lost sister lineage,” Ni said.

Stringer thinks that Homo longi – along with other hominin fossils previously found in China that had not been assigned a species – is part of a distinct population of human ancestors that thrived in East Asia during the Middle Pleistocene.

Homo longi dragon man
An illustration of Homo longi, or “Dragon Man,” a new human ancestor discovered in China.

However, Ian Tattersall, an anthropologist with the American Museum of Natural History who was not involved in the research, told Insider that he’s unsure Homo longi is really a sister lineage to modern humans. That’s because skulls from Homo sapiens have distinct foreheads, and the bones that make up the face are retracted from the forehead, Tattersall said. He thinks “Dragon Man” is missing that characteristic.

“I’d reserve judgement on the claim of a particularly close relationship with Homo sapiens,” he said.

Tattersall said he doesn’t have a problem with assigning the skull to a new species, though.

‘Dragon Man’ could be a Denisovan

denisovan
A portrait of a juvenile female Denisovan.

It’s possible, Stringer said, that Homo longi is actually a member of the Denisovan population – a human ancestor that lived in Asia from 500,000 to 30,000 years ago. If that were the case, he added, “then we know that they did interbreed with both Neanderthals and our species, and some of the Harbin group’s DNA could still be in some Homo sapiens populations today.”

Homo longi dragon man
An illustration of Homo longi, or “Dragon Man.”

To investigate that possibility, researchers could collect ancient DNA from the skull for further testing.

“But as the extraction process is somewhat destructive, it needs to be considered very carefully for this precious fossil,” Stringer said.

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