Scientists on Friday announced that a massive
fossilized skull that is at least 140,000 years old is a new species of ancient
human, a finding that could potentially change prevailing views of how — and
even where — our species, Homo sapiens, evolved.
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The skull belonged to a mature male who had a huge brain,
massive brow ridges, deep set eyes and a bulbous nose. It had remained hidden
in an abandoned well for 85 years, after a laborer came across it at a
construction site in China.
The researchers named the new species Homo longi and gave it
the nickname “
Dragon Man,” for the Dragon River region of northeast China where
the skull was discovered.
The team said that Homo longi, and not the Neanderthals, was
the extinct human species mostly closely related to our own. If confirmed, that
would change how scientists envision the origin of Homo sapiens, which has been
built up over the years from fossil discoveries and the analysis of ancient
DNA.
But a number of experts disputed this conclusion, published
in three papers that provided the first detailed look at the fossil.
Nevertheless, many still thought that the find could help scientists
reconstruct the human family tree and how modern humans emerged.
All the experts who reviewed the data in the studies said it
is a magnificent fossil.
“It’s a beautiful thing,” said John Hawks, a
paleoanthropologist at the University of Wisconsin-Madison. “It’s very rare to
find a fossil like this, with a face in good condition. You dream of finding
this stuff.”
In 1933, a laborer working at a bridge construction site in
the city of Harbin discovered the peculiar skull. It’s likely that the man —
whose name has been withheld by his family — recognized that he had found a
scientifically important specimen. Just four years earlier, researchers had
found another humanlike skull, nicknamed Peking Man, near Beijing. It appeared
to link the people of Asia to their evolutionary forerunners.
Rather than hand over the new skull to the Japanese
authorities who occupied northeast China at the time, the laborer chose to hide
it. He did not mention the skull to anyone for decades. In an account of the
fossil’s discovery, the authors of the new papers speculated that he was
ashamed of having worked for the Japanese.
Shortly before his death in 2018, the laborer told his
family about the fossil. They went to the well and found it. The family donated
it to the Geoscience Museum of Hebei GEO University, where scientists
immediately could see that it had been exquisitely well preserved.
In the papers published Friday, the researchers argued that
Homo longi appears to have been an adult of great size. His cheeks were flat
and his mouth broad. The lower jaw is missing, but the researchers infer from
the Dragon Man’s upper jaw and other fossil human skulls that he likely lacked
a chin. They say that his brain was about 7% larger than the average brain of a
living human.
The researchers argue that Dragon Man’s combination of
anatomical features are found in no previously named species of hominin, the
lineage of bipedal apes that diverged from other African apes. They later
evolved into larger-brained species that set the stage for Homo sapiens to
expand across the entire globe.
“It’s distinctive enough to be a different species,” said
Christopher Stringer, a paleoanthropologist at the Natural History Museum in
London and co-author of two of the three Dragon Man papers.
The scientists analyzed the chemical composition of the
fossil, and determined it was at least 146,000 years old, but no older than
309,000 years.
Today, the planet is home to just one species of hominin —
Homo sapiens. But Dragon Man existed at a time when a number of drastically
different kinds of hominins coexisted, including Homo erectus — a tall human
with a brain two-thirds the size of our own — as well as tiny hominins
including Homo naledi in South Africa, Homo floresiensis in Indonesia and Homo
luzonensis in the Philippines.
The oldest Homo sapiens fossils also date to this time.
Neanderthals — which shared our large brain and sophisticated toolmaking —
ranged from Europe to Central Asia during the period when Dragon Man may have
lived.
In recent years, studies of fossil DNA have also revealed
yet another humanlike lineage in this period, the Denisovans. The DNA came
largely from isolated teeth, chipped bones and even dirt. Those remains are not
enough to show us what Denisovans looked like.
The most promising fossil yet found that could be evidence
of Denisovans came from a cave in Tibet: a massive jaw with two stout molars,
dating back at least 160,000 years. In 2019, scientists isolated proteins from
the jaw, and their molecular makeup suggests they belonged to a Denisovan,
rather than a modern human or Neanderthal.
This molecular evidence — combined with fossil evidence —
suggests that the common ancestors of Homo sapiens, Neanderthals and Denisovans
lived 600,000 years ago.
Our lineage split off on its own, and then 400,000 years
ago, Neanderthals and Denisovans diverged. In other words, Neanderthals and
Denisovans were our closest extinct relatives. They even interbred with the
ancestors of modern humans, and we carry bits of their DNA today.
But many puzzles still endure from this stage of human
history — especially in East Asia. Over the past few decades,
paleoanthropologists have found a number of fossils, many incomplete or
damaged, that have some features that make them look like our own species and
other features that suggest they belong elsewhere on the hominin family tree.
Katerina Harvati, a paleoanthropologist at the University of
Tübingen in Germany who was not involved in the new study, said that the Dragon
Man skull could “help clarify some of the confusion.”
To figure out how Homo longi fits into the human family
tree, the scientists compared its anatomy with 54 hominin fossils. The
researchers found that it belongs to a lineage that includes the jaw in Tibet
that has been identified as a Denisovan.
The skull was even more similar to a portion of a skull
discovered in 1978 in the Chinese county of Dali, dating back 200,000 years.
Some researchers thought the Dali fossil was of our own species, while others
thought it belonged to an older lineage. Still others even called the fossil a
new species, Homo daliensis.
The authors of the new studies argue that Dragon Man, the
Tibetan jaw and the Dali skull all belong to a single lineage — one that is the
closest branch to our own species. While Homo longi had distinctive features,
it also shared traits with us, such as a flat face tucked under its brow rather
than jutting out, as was the case with Neanderthals.
“It is
widely believed that the Neanderthal belongs to an extinct lineage that is the
closest relative of our own species. However, our discovery suggests that the
new lineage we identified that includes Homo longi is the actual sister group
of H. sapiens,” Xijun Ni, a co-author of the studies and a
paleoanthropologist at the Chinese Academy of Sciences and Hebei GEO University
said in a news release.
Those conclusions are spurring debate among
paleoanthropologists — including the authors of the new papers.
Some of the debate concerns what to call Dragon Man.
Scientists follow strict rules about naming new species. That would require
Dragon Man to share a name with the Dali skull, if they are as similar as the
authors claim.
“In my
view, it is a distinct species which I would prefer to call Homo daliensis,” Stringer said.
Other experts thought the similarity between the Tibetan
jaw, with the Denisovan-like proteins, and the skull from Harbin pointed to
Dragon Man’s real identity.
“When I first saw the picture of the fossil I thought, now
we finally know what Denisovans looked like,” said Philipp Gunz, a
paleoanthropologist at Max Planck Institute for Evolutionary Anthropology in
Leipzig, Germany.
Karen Baab, a paleoanthropologist at Midwestern University
in Arizona, agreed: “Harbin is better understood as a Denisovan.”
An assortment of clues point that way. The tooth on Dragon
Man’s upper jaw has the same massive shape as the one on the Denisovan jaw
found in Tibet, for example. Both lack a third molar. Dragon Man also lived in
Asia at the same time that Denisovan DNA tells us that they were in the same
place.
Even if Dragon Man is a Denisovan, there would be more
puzzles to solve. The DNA of Denisovans clearly shows that their closest
cousins were Neanderthals. The new study, based instead on fossil anatomy,
indicates instead that Homo longi and Homo sapiens are more closely related to
each other than to Neanderthals.
“I think that the genetic data in this case is more reliable
than the morphological data,” said Bence Viola, a paleoanthropologist at the
University of Toronto, who was not involved in the new study.
“Obviously, something doesn’t match,” Stringer acknowledged.
“The important thing is the recognition of a third human lineage in East Asia,
with its own distinctive combination of features.”
One way to solve the mystery of Dragon Man would be to get
DNA from his remarkable skull. Stringer said he is ready for more surprises:
“It’s going to be a more complicated plot.”
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