The DNA of a small 2cm bone fragment found in the Denisova Cave in Russia revealed that the owner of the bone was a young girl.
Another bone fragment was known to be a girl born to a Neanderthal mother and a Denisovan father.
These facts have been made possible through the DNA analysis of Doctor Svante Pääbo's research team,
awarded the 2022 Nobel Prize in Physiology or Medicine.
This video introduces the process of restoring Denisovans from bone fragments and the process of evolution and spread.
Where did we humans come from?
Some of you may be looking for an answer to this question in religion.
Others will look for it in science.
You may not be interested in this question at all.
However, no matter how hard we try to admit it,
billions of years of life history and millions of accounts are encrypted and recorded in our bodies.
Many archaic humans appeared and disappeared repeatedly.
Denisovans, close relatives of modern humans who survived together with Neanderthals until only 30,000 to 40,000 years ago,
who are they?
Would you like us to find out about them?
Now, let's go on a journey to find their origins.
Denisova Cave is located in south-central Siberia, Russia,
in the Altai Mountains near the borders of Kazakhstan, China, and Mongolia.
It is named after Denis, a Russian hermit who lived here in the 18th century.
The cave was first inspected for fossils in the 1970s by Russian paleontologist Nikolai Ovodov,
who was looking for remains of canids.
In the summer of 2008, Russian scientists Michael V. Shunkov and Novosibirsk Akademgorodok found many bone fragments and artifacts,
such as bracelets, rings, and beads, in the Denisova Caves.
Most have been thought to be the bones of prey hunted by cave lions during the Ice Age.
Using a new and improved 'mass spectrometry' method that can extract proteins from fossils in many bone fragments,
what is believed to be the little finger bone of a female hominin is found.
A complete skull has yet to be found.
And among the artifacts, there were unusual things estimated to be 40,000 to 50,000 years old.
Specifically, there was a color-changing perforated stone bracelet and a bone needle about 8 centimeters long (3.15 inches).
This predates the previous one by 10,000 to 15,000 years.
These ornaments suggest that there was a hierarchy among the members.
Needles indicate that there was a skill to make clothes and shoes.
This means they had a much higher level of technology than we imagined.
While there has been some debate as to whether or not the artifacts were Denisovans,
it is not disputed that the bone fragments were Denisovans.
At the beginning of the excavation,
Russian scholars thought that the bone fragments belonged to either Neanderthals or modern humans.
For a more accurate analysis, they request an analysis from Professor Svante Paabo's team at the Max Planck Institute for Evolution in Germany.
At this time, Professor Svant Paabo's team was analyzing Neanderthal by developing a technology to extract the genome from old bones and analyze its base sequence
The latest advances in molecular biology have made this analysis possible.
In this assay, mitochondrial DNA extracted from bone fragments was used.
Mitochondria exist in tens to hundreds in a cell,
and there is a considerable amount in the whole body,
so the probability of finding a relatively intact sample is high.
What were the analysis results?
At first, the research team thought there might be an error in their analysis
because the DNA from the bones was neither Neanderthal nor Homo sapiens.
So, they secondly conduct genome analysis of the entire cell nucleus.
In 2012, the whole analyzed genome was published,
and they were named Denisovans.
They were more like Neanderthals than modern humans.
Five Denisovan individuals have been found in Denisova Cave.
The object with the third finger bone was designated as Denisova 3 or X Woman.
The tooth of an adult male excavated in 2000 was Denisova 4,
and the tooth of an adult male excavated in 2015 was determined to be Denisova 8.
In addition, the molar tooth of an adolescent female excavated in 2017 is named Denisova 2.
Mitochondrial DNA analysis revealed that Denisova 2 was the oldest,
followed by Denisova 8, and Denisova 3 and 4 lived simultaneously.
The flat face you see on the screen, and the slightly protruding forehead is the face of a 13-year-old Denisovan girl,
a cousin of a modern human who lived 70,000 years ago.
How did they figure out what Denisovans looked like?
The Denisovans, who lived in Siberia and became extinct from 200,000 to 30,000 years ago,
have been shrouded in mystery.
The fossils of Denisovans discovered so far are a little finger, a tooth, and a lower jaw.
A research team led by Liran Carmel of the Hebrew University in Israel made the first detailed restoration.
The thesis written by this research team was published in the international journal 'Cell' in September 2019.
The face was reconstructed thanks to DNA from the bones of the fingers.
The research team analyzed primates' DNA to determine which parts determine their appearance.
It is known that males have XY and females have XX chromosomes.
To observe this chromosome in a cell, the cell must be alive,
but this chromosome could not be found in old Denisovans.
Liran Carmel's research team analyzes these bones
through a sequencing method that compares and restores Denisovan's DNA with DNA databases of modern humans and primates.
As a result of the analysis, no trace of the Y chromosome was found,
so it was concluded that the owner of this bone was female.
And we developed an algorithm that can infer the appearance by looking at the DNA and observing
how the corresponding part looks when activated or deactivated.
This research team deciphers the DNA methylation of ancient samples and restores the structure of the human body with 85% accuracy.
Denisovans, inferred through this technology, have a wider pelvis than modern humans and darker skin, eyes, and hair.
Here is evidence of interbreeding between Denisovans and Neanderthals.
The DNA of a bone fragment called Denisova 11, excavated in 2010 but stored,
was analyzed in 2016 and announced in 2018.
This bone has been identified as part of a Denisovan leg or arm bone.
Denisova 11's DNA was examined by Doctor Svante Pääbo's research team at the Max Planck Institute for Evolutionary Anthropology.
In 2022, Doctor Svante Pääbo was awarded the Nobel Prize in Physiology or Medicine "for his discoveries concerning the genomes of extinct hominins and human evolution."
His research team determined that Denisova 11 was a girl who died 90,000 years ago at the age of at least 13 years.
That's why Denisova 11 is also called Denny.
The whole genome sequence was analyzed,
and surprisingly, she was born to a Neanderthal mother and a Denisovan father.
17% of her DNA was from Neanderthals.
Her Neanderthal DNA was the closest to that of a European Neanderthal who lived in Vindija Cave in Croatia.
It turns out that she and her dad's DNA was of Denisovan ancestry, with some descending from Neanderthal ancestry.
It drew public attention because it was the first remains to prove that there was interbreeding between ancient humans.
The Vindija Caves are 4870 Kilometers from the Denisova Caves.
This is also evidence suggesting that Neanderthals living in Europe migrated to Asia several times over thousands of years.
Have Denisovan skeletons been found anywhere other than Denisova Cave?
Denisovan remains have not been found as many as Sapiens or Neanderthals.
However, analysis of partial mandibles and molars recently excavated in China and Laos confirmed that they belonged to Denisovans.
Partial mandibles were discovered in 1980 at Baishiya Cave in Xiahe, China,
and identified as Denisovans in a paper published in 2019.
It is estimated that they lived in this area 160,000 years ago.
DNA extraction from the mandible with two attached molars was unsuccessful,
but they did identify an ancient proteome that survived in the dentin of one of the molars.
This proteome was closest to Denisova 3 in the Denisova Cave.
The molars excavated from the Tam Ngu Hao 2 cave in northern Laos in 2018 were also estimated to be Denisovans in a paper published in Nature in 2022.
As a result of analyzing the degree of development of the teeth,
it was a girl between 3.5 and 8.5 years old.
These two statements suggest that in Asia, Sapiens lived alongside other species,
such as Denisovans and Neanderthals, and interbreeding occurred between them.
Did interbreeding occur with modern humans, Homo sapiens?
A paper was published in 2011 showing that modern humans also interbred with Denisovans.
Among modern humans, Melanesians, including Papua New Guinea, the aborigines of Australia,
are known to have 4-6% of Denisovan-derived DNA.
It is said that 0.2% of East Asian DNA comes from Denisovans.
According to a paper published in the journal Current Biology in 2021,
the Ayta Magbukun people of the Philippines have the highest level of Denisovan ancestry.
The authors of this paper performed a comprehensive analysis of the ancient origin of 118 Filipino ethnic groups,
where Ayta Magbukon has 30%-40% more Denisovan ancestry than Australopapuans.
Tibetans also have genes from Denisovans.
In particular, a gene called EPAS1, necessary for adapting to high altitudes is derived from Denisovans.
it was found that genes that enhance immunity were found in common among the indigenous people east of the Wallace Line.
A 2021 study found that analyzing the blood types of one Denisovan and three Neanderthals found new clues about this population's evolutionary history, health, and vulnerability.
A research team from the French National Center for Scientific Research (CNRS)
and the University of Aix-Marseille published their findings in the open-access journal PLOS ONE.
Each archaic human had blood type alleles or different versions of the same gene,
consistent with the idea that Neanderthals and Denisovans originated in Africa.
The authors also stressed that "analysis of blood group systems for Neanderthals and Denisovans confirms their African origins
as well as their weakness in fertility rates and vulnerability to viral infections that can lead to high infant mortality."
This pattern is consistent with evidence that Neanderthals' low genetic diversity and low reproductive success ultimately led to extinction.
To do so, shall we examine the evolution and migration process of the Denisovans?
Homo heidelbergensis is typically considered the direct ancestor of Denisovans and Neanderthals,
and sometimes modern humans.
Due to the substantial divergence in dental anatomy,
hey may have split before characteristic Neanderthal dentition evolved about 300,000 years ago.
A 2018 study found that East Asians now have Denisovan DNA from two groups.
One group is Denisovan DNA found in the Papuan genome,
and the other is located in Denisovans who lived in the Denisovan Cave.
A 2019 study also suggests that a third wave of migration spread to East Asia.
It is thought that they entered Oceania before and after the separation of Eurasians and Oceanians.
That period was about 58,000 years ago.
The Papuans and the Australian Aborigines separated about 37,000 years ago.
It is possible that this separation occurred at Wallcea,
given the present Denisovan DNA distribution.
The discovery of a 7,200-year-old Toalean girl with Denisovian DNA in Sulawesi makes Sundaland another strong potential candidate.
Early Sundanese hunter-gatherers had very little Denisovan DNA.
Wallacea is the biogeographical name for a group of predominantly Indonesian islands separated from the Asian and Australian continental shelves by a deep-sea strait.
The Wallacea group includes Sulawesi, Lombok, Sumbawa, Flores, Sumba, Timor, Halmahera, Buru, and Seram.
To the left of Wallacea is the Sunda Shelf,
and to the west is the Sahul Shelf,
which includes Australia and New Guinea.
Both of these continental shelves were landed during the Last Glacial Maximum.
The Denisovans crossed the Wallace Line into Oceania.
Wallace Line is a line separating the biogeographical area of Asia from Wallacea,
the transitional area between Asia and Australia.
The western side of this line contains organisms related to Asian species,
while the eastern side contains a mixture of species native to Asia and Australia.
The line passes through between Borneo and Sulawesi in Indonesia
and the Strait between Bali and Lombok.
The distribution of large land mammals on either side of this line is different.
With few exceptions, many birds also differ in their observed species along this line.
The Denisovans migrated to the Tibetan Plateau,
and some moved to Sundaland, where they stayed.
Interbreeding with Homo sapiens likely took place in Sundaland.
And their descendants sailed the depths of the Wallace Line to Oceania.
Another group staying in Tibet headed north to the Denisova Caves.
And in this group, a Denisovan man married a Neanderthal woman
and had a half-Neanderthal, half-Denisovan daughter, Denny.
Denny left the secret of her birth in a tiny piece of bone.
Doctor Svante Pääbo, awarded the 2022 Nobel Prize,
deciphered the mystery of Denny's birth engraved on this bone fragment, which we all know.
So far, we have briefly looked at the long history of more than 90,000 years.
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