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Ancient Human Fossil Jaw Discovered off Taiwan Coast
For decades, fishermen operating off the shores of Taiwan have occasionally retrieved fossils in their fishing nets. These relics often include the bones of elephants, buffalo, and other large mammals that roamed the region tens of thousands of years ago, when lower sea levels connected Taiwan to mainland Asia via a land bridge. Among these finds, a particularly unusual fossil surfaced in 2010, sparking intense scientific curiosity and leading to a groundbreaking discovery about ancient humans.
Mysterious Jawbone Puzzles Scientists
In 2010, a Taiwanese paleontologist was presented with a peculiar discovery: a fossil resembling half of a gorilla’s mandible. This underwater jawbone, unlike typical animal fossils recovered by fishermen, presented an anthropological puzzle that intrigued researchers for years.
Initially perplexing experts, the mystery surrounding this fossil jaw has now been resolved. Researchers announced on Wednesday that the jawbone belonged to a Denisovan, an archaic human group closely related to Neanderthals. This significant finding extends the geographical reach of known Denisovan fossils, previously identified primarily in Siberia and Tibet.
“Indeed, Denisovans were present as far east as the coast,” stated Frido Welker, a molecular anthropologist and a contributing author to the recent study, highlighting the expanded understanding of Denisovan distribution.
Penghu 1: Initial Examination and Uncertainty
Dr. Chun-Hsiang Chang, a paleontologist at Taiwan’s National Museum of Natural Science, first encountered the jawbone in 2010 through a private collector. Upon inspection, Dr. Chang immediately recognized that the fossil was not from a gorilla or ape. While great apes have U-shaped mandibles, this fossil jaw angled outward from the chin, a characteristic more akin to human jaws.
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However, the jaw lacked the prominent chin typically observed in modern humans. “At that time, my assessment was that it resembled a human jaw, but not that of a contemporary human,” Dr. Chang recounted. “Recognizing its potential importance, I urged the private collector to loan it to our museum for further investigation.”
Deciphering the Fossil’s Origins
Over the subsequent five years, Dr. Chang collaborated with an international team of scientists to analyze the anatomy of the jawbone, which they designated Penghu 1, named after the Penghu Channel where it was discovered. Its general form was similar to that of extinct human relatives known to have inhabited Asia over a million years ago. Still, Penghu 1 also presented unique features, notably its substantial teeth.
Determining the precise age of Penghu 1 posed a significant challenge, as the exact seabed location of its origin was unknown. To address this, Dr. Chang and his colleagues conducted chemical analyses of the jaw, revealing a composition comparable to fossils of a hyena species that evolved in eastern Asia approximately 400,000 years prior.
Land Bridges and Ancient Human Migration
Geological timelines indicated that around 400,000 years ago, Taiwan was separated from the Asian continent by water. However, approximately 190,000 years ago, a significant drop in sea level created a land bridge, persisting until about 130,000 years ago. Sea levels then rose again until around 70,000 years ago when another land bridge emerged, lasting until 10,000 years ago. Dr. Chang and his team hypothesize that the Penghu 1 individual lived during one of these periods of lowered sea level and terrestrial connection.
Denisovans: Unveiling a Mysterious Human Lineage
One compelling possibility considered was that Penghu 1 belonged to the Denisovans, an enigmatic group of ancient humans. Denisovans were initially identified in 2010 through the analysis of fossils from Denisova Cave in Siberia. Examination of a tooth and a finger bone revealed ancient DNA with unique genetic markers, unveiling a previously unknown human lineage.
Further research indicated that Denisovans, Neanderthals, and modern humans share a common ancestor who lived in Africa roughly 600,000 years ago. The ancestors of Neanderthals and Denisovans migrated out of Africa, with these two groups diverging approximately 400,000 years ago. Neanderthals subsequently spread westward into Europe.
Tracing Denisovan Expansion Across Asia
Mapping the dispersal of Denisovans has proven more challenging. For many years, the limited Denisovan fossil record consisted only of the teeth and bone fragments unearthed in Denisova Cave. However, a significant clue emerged from the genetic profiles of present-day human populations. A notable percentage of individuals in East Asia and the Pacific Islands carry traces of Denisovan DNA. This genetic legacy suggests that Denisovans, before their extinction, interbred with Homo sapiens in East Asia, implying a geographical range extending far beyond Siberia.
Dr. Chang and his fellow researchers observed that a tooth from the Penghu 1 jaw exhibited similarities to a tooth from Denisova Cave. However, this dental resemblance alone was insufficient to establish a definitive link. Attempts to extract DNA from the Penghu 1 jaw proved unsuccessful, which was not unexpected given its long submersion on the seabed.
Protein Analysis Breakthrough
Following the initial publication of Dr. Chang’s team’s analysis in 2015, Penghu 1 remained an intriguing but unclassified hominin fossil within museum collections. “Our investigation reached a standstill,” Dr. Chang acknowledged.
In subsequent years, Dr. Welker and other scientists pioneered innovative techniques for extracting ancient proteins from fossilized remains. These advancements revealed that even fossils devoid of detectable DNA may still preserve protein fragments.
Dr. Welker applied these protein retrieval methods to a 160,000-year-old jawbone discovered in a high-altitude cave in Tibet. In 2019, his team announced that the Tibetan fossil contained fragments of ancient collagen and other proteins.
These proteins displayed similarities to those of modern humans but also exhibited distinct variations, suggesting that the Tibetan jaw originated from a Denisovan individual.
This breakthrough discovery prompted Dr. Welker to examine existing scientific literature for other Asian fossils resembling the Tibetan jaw that might be suitable for protein analysis.
Penghu Mandible’s Denisovan Identity Confirmed
“That is how the Penghu mandible resurfaced on my radar,” Dr. Welker explained.
Both the Tibetan and Taiwanese jawbones were characterized by remarkably large teeth. Dr. Welker and his colleagues contacted Dr. Chang to request a re-examination of Penghu 1. In 2023, Dr. Chang and his team transported the jawbone to Copenhagen for advanced protein analysis. The subsequent analysis revealed protein fragments uniquely identifiable as Denisovan.
“From the initial publication of the Penghu mandible, many of us suspected it might be Denisovan, primarily due to its geographical location and estimated age,” noted Bence Viola, a paleoanthropologist at the University of Toronto, who was not directly involved in this study. “However, assumptions need validation, and concrete data is essential to confirm such hypotheses.”
Further confirmation came from enamel protein fragments within the teeth. Modern humans possess an enamel gene on their X chromosome, with males carrying a slightly different version on their Y chromosome. The Denisovan jaw exhibited the Y-chromosome version, indicating it belonged to an adult male.
The large tooth morphology observed in both Denisovan jaws may prove to be a characteristic of male Denisovans. Female Denisovans might have possessed a more gracile skeletal build—though further evidence is required for conclusive determination.
Expanding the Denisovan Geographic Range and Diversity
The discovery of additional Denisovan fossils has the potential to significantly expand the understanding of their geographical distribution. In 2022, researchers identified a 160,000-year-old tooth in a cave in Laos that closely resembled a tooth from the Tibetan Denisovan jaw. Survival in this region would have required adaptation to a tropical forest environment, contrasting sharply with the Siberian landscape.
Although the Laotian tooth did not yield DNA and protein fragments provided limited taxonomic clarity, the cave site and neighboring caves contain numerous teeth awaiting comprehensive analysis. Moreover, traces of other Denisovans may remain undiscovered within museum collections.
Current evidence strongly suggests that Denisovans were capable of thriving across vast distances and diverse environments. Janet Kelso, a paleoanthropologist at the Max Planck Institute for Evolutionary Anthropology, emphasized the distinctions between the Penghu 1 proteins and those from Tibet. This suggests that as Denisovans dispersed across varied environments, they evolved into genetically distinct populations, adapting to local conditions.
“There are still extensive aspects to uncover about Denisovans,” she concluded, underscoring the ongoing nature of paleoanthropological research into this fascinating ancient human lineage.