Jawbone discovery adds to the mystery of our Denisovan ancestors

In the shallows off Taiwan’s western coast, a centuries-old jawbone fossil lay hidden beneath the sea. It wasn’t buried in a cave or preserved in a mountain. Instead, it rested quietly in the sediment of the Penghu Channel – until chance and curiosity brought it to light.

What began as a fisherman’s haul would soon rewrite the story of a long-lost branch of humanity. Scientists now confirm that this ancient jawbone belonged to a Denisovan, one of the most mysterious human relatives ever identified.

Jawbone fossil from rare Denisovan group

The Denisovans are an extinct group of archaic humans, first identified in 2010. Their name comes from the Siberian cave where their remains were originally discovered.

They are neither Neanderthals nor modern humans, but something distinct. They share ancestors with both of these hominins, and have left genetic remnants in living populations today. Much about them remains uncertain, because their physical fossils are extremely rare.

“Denisovan fossils are very scarce,” said study co-author Takumi Tsutaya at the Graduate University for Advanced Studies in Japan.

Until recently, their known fossils included only a few teeth, jaw fragments, and a finger bone. These remains came mostly from Denisova Cave in southern Siberia and a cave in Tibet.

Hints of Denisovan presence in Laos and China have emerged, but no direct molecular evidence had confirmed those suspicions. That changed with the jawbone, which is now known as Penghu 1.

Accidental discovery turns into treasure

Penghu 1’s story began not in a lab, but on a fishing boat. In the early 2000s, a trawler operating near the Taiwan Strait dredged up the fossil from the seabed.

It made its way to an antique shop, where it sat unrecognized until 2008, when a collector noticed its potential and donated it to Taiwan’s National Museum of Natural Science.

The fossil jawbone’s location – once part of the Asian mainland during times when sea levels were lower – places it in an area that could have been accessible to ancient humans.

Initial attempts to study the jawbone were limited. The fossil was too degraded to yield ancient DNA, which is typically the most reliable way to identify archaic human lineages. However, scientists from Taiwan, Japan, and Denmark took a different route.

Using advanced protein analysis, they found molecular signatures preserved in the fossil’s bone and tooth enamel.

Jawbone proteins match Denisovans

Rather than rely on DNA, the team turned to palaeoproteomics, a method that involves studying ancient proteins. From just 25 milligrams of jawbone, they recovered 4241 amino acid residues – an unusually high number for such old material.

These proteins included bone collagen and enamel proteins like amelogenin and enamelin. Within these, the researchers found two Denisovan-specific protein variants that sealed the identification.

One key marker was a variant of the protein ameloblastin (M273V) that is rarely found in modern humans but is present at high frequency in populations with known Denisovan ancestry.

Another protein marker was found in collagen (COL1A2; R996K), and this had previously been identified in Siberian and Tibetan Denisovans. Together, these markers matched closely with those found in Denisova 3, a well-studied Denisovan fossil from Siberia.

Penghu 1 also revealed its biological sex. Scientists identified amelogenin Y, a protein variant found only in males. The enamel peptides matched 11 of 23 diagnostic sites, allowing them to classify the jawbone’s owner as male with confidence.

Jawbone fossil shows possible male traits

The Denisovan identity of Penghu 1 adds to our growing understanding of their morphology. Alongside other known Denisovan fossils, the jawbone helps define a set of physical traits.

These include a low but thick mandibular body, wide dental arcade, large molars, and unusually strong premolar roots.

Some molars showed signs of extra roots and the absence of wisdom teeth – features that are shared with other confirmed Denisovan fossils from Tibet and Siberia.

Interestingly, all well-preserved Denisovan jawbones and teeth that have been found so far – Denisova 4, Denisova 8, Xiahe 1, and now Penghu 1 – belonged to males.

This raises a question.

Were robust jaws a male trait, or do they reflect the general Denisovan condition? Female specimens, like the gracile Jinniushan fossil from northeast China, might offer clues if their Denisovan identity is confirmed through molecular analysis.

From Siberian caves to island shores

Perhaps the most remarkable aspect of this discovery is its location.

Penghu lies over 4000 kilometers southeast of the Denisova Cave and more than 2000 kilometers from Xiahe in Tibet. Denisovans now appear to have occupied a vast range – from cold, mountainous regions to tropical, coastal lowlands.

Genetic studies had previously suggested that Denisovans contributed DNA to modern human populations in East and Southeast Asia, including those in the Philippines.

The jawbone offers direct evidence that Denisovans not only passed through, but lived in such environments.

Penghu 1’s discovery confirms that Denisovans thrived in conditions unlike those associated with Neanderthals, who lived mostly in Europe and parts of western Asia.

The ability to survive in cold highlands and warm islands speaks to the impressive adaptability of these ancient hominins.

Denisovan jawbone reshapes story of evolution

This fossil shifts how we understand Denisovan evolution and dispersal. Its morphology supports the idea that Denisovans evolved unique traits after splitting from Neanderthals over 400,000 years ago.

These weren’t just random primitive features. They represent a distinct evolutionary path within the genus Homo – one that ran parallel to our own.

“We can identify Neanderthal elements and Denisovan elements” in the DNA of some people alive today, said Tsutaya.

Now, with Penghu 1, scientists can trace some of those Denisovan elements back to a real individual who once lived, breathed, and chewed with the powerful jaw found beneath the waves.

The fossil’s protein record brings Denisovans into sharper focus – not just as genetic contributors to our own genomes, but as people with faces, bones, and stories waiting to be uncovered.

The study was published in the journal Science.

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