(By Dr. Joseph D. Lim and Dr. Kenneth Lester Lim, BS-MMG, DDM, MSc-OI)
A FOSSIL tooth unearthed in Cobra Cave in Laos puts mystery humans in Southeast Asia, including the Philippines.
The tooth belong to an ancient human called the Denisovan who was previously only known from the icy northern latitudes – in Siberia’s frigid Denisova Cave in the Altai mountains.
An international team of researchers have shown these long-lost relatives of Homo sapiens inhabited a wider range of environments than was previously known. They confirm hints found in the DNA of modern human populations from Southeast Asia and Australasia.
The researchers include Kira Westaway is Associate professor, Macquarie University (Sydney); Mike W. Morley is Associate Professor, Flinders University (Adelaide); and Renaud Joannes-Boyau is Associate Professor, Southern Cross University (Australia).
Little is known about the Denisovans, distant cousins of modern humans, except that they once lived in Asia, were related to and interacted with the better-known Neanderthals, and are now extinct, they write in The Conversation.
The first traces of Denisovans were only found in 2010, with the discovery of an innocuous finger bone in a remote Denisova Cave in Siberia. The extreme cold of the cave meant some ancient DNA was preserved in the bone – and the DNA revealed the finger had belonged to an unknown species of human.
This discovery changed the course of human evolutionary studies, and the newly discovered humans were named Denisovans after the cave where the fossil was found.
Meanwhile, it was found that genes from Denisovans survived in modern day people from Southeast Asia and Australasia. This implied that the Denisovans had dispersed over a far larger area than anticipated.
The hunt was on to find more evidence of these humans outside Russia, but scientists had no idea what they actually looked like, the researchers write. “For the first time in history we knew more about a human’s DNA than their anatomy!”
The next twist came when a 160,000-year-old Denisovan jawbone surfaced on the Tibetan Plateau, giving the scientific community a tantalizing glimpse of what the bodies of these ancient humans were like and where they lived.
In 2018 an international (Laos-French-American-Australian) team in northern Laos in 2018 unearthed, so to speak, a human tooth (a lower permanent molar) in the cave sediments in Cobra Cave. They could not initially identify what species of human it came from.
The humid conditions in Laos, however, meant that the ancient DNA was not preserved. They did find ancient proteins that suggested the tooth came from a young, likely female, human – probably between 3.5 and 8.5 years old who lived around 150,000 years ago.
After very detailed analysis of the shape of this tooth, the researchers identified many similarities to the Denisovan teeth found on the Tibetan Plateau. This suggested the tooth’s owner was most likely a Denisovan who lived between 164,000 and 131,000 years ago in the warm tropics.
“This fossil represents the first discovery of Denisovans in Southeast Asia, and shows that Denisovans were at least as far south as Laos,” the researchers now say. “This is in agreement with the genetic evidence found in modern day Southeast Asian populations.”
The Denisovans may have been just at home in the balmy tropical climates of Laos as the icy conditions of northern Europe and the high-altitude environments of the Tibetan Plateau, the researchers observe.
“This suggests the Denisovans were very good at adapting to diverse environments,” they say. “It would seem that Southeast Asia was a hotspot of diversity for humans.”
At least five different species set up camp here at different times: Homo sapiens, Homo erectus, the Denisovans/Neanderthals, Homo floresiensis – and Homo luzonensis.
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Dr. Joseph D. Lim, Ed. D., is the former Associate Dean of the College of Dentistry, University of the East; former Dean, College of Dentistry, National University; Past President and Honorary Fellow of the Asian Oral Implant Academy; Honorary Fellow of the Japan College of Oral Implantologists; Honorary Life Member of the Thai Association of Dental Implantology; and Founding Chairman of the Philippine College of Oral Implantologists. For questions on dental health, e-mail jdlim2008@gmail.com or text 0917-8591515.
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Dr. Kenneth Lester Lim, BS-MMG, DDM, MSc-OI, graduated Doctor of Dental Medicine, University of the Philippines, College of Dentistry, Manila, 2011; Bachelor of Science in Marketing Management, De la Salle University, Manila, 2002; and Master of Science (MSc.) in Oral Implantology, Goethe University, Frankfurt, Germany, 2019. He is an Associate Professor; Fellow, International Congress of Oral Implantologists; Member, American Academy of Implant Dentistry and Fellow, Philippine College of Oral Implantologists. For questions on dental health, e-mail limdentalcenter@gmail.com./PN
