A rare glimpse of our first ancestors in mainland Southeast Asia

• • Tam Pà Ling, a cave in northern Laos, reveals new secrets about our earliest human journeys from Africa through to Australia.
  • Between 86,000 and 68,000 years ago, modern humans passed by a cave in mainland Southeast Asia on their way through Asia to become Australia’s First People.
  • Evidence for a human presence in this region lasting at least 56,000 years was found in approximately seven metres of cave sediment.
  • This evidence demonstrates our abilities to move through forested areas and along inland river systems, and could represent a previously-used migration path among our ancestors.

  How is a fossil discovered in a cave in northern Laos linked to stone tools crafted in northern Australia? The solution lies within us. As our ancient Homo sapiens predecessors ventured from Africa to Australia through Southeast Asia, they left behind traces of their existence in the shape of human fossils, which gradually accumulated throughout countless years within a cavernous depth.

  The most recent findings from Tam Pà Ling cave in northern Laos, disclosed by a collaborative group of Laotian, French, American, and Australian scientists and documented in Nature Communications, undeniably establish that Homo sapiens migrated from Africa to Asia via Arabia much earlier than previously believed.

  Additionally, the evidence affirms that our predecessors did not solely navigate along coastlines and islands during their migration. They also traversed through densely forested areas, likely following river valleys as well. Subsequently, certain individuals ventured further into Southeast Asia, eventually becoming the Indigenous First Peoples of Australia.

  "Tam Pà Ling assumes a pivotal role in the narrative of human migration across Asia, yet its true significance and worth are only now being acknowledged," stated Assistant Professor Fabrice Demeter, a palaeoanthropologist from the University of Copenhagen and one of the primary authors of the research paper.

  The project received contributions from three Australian universities. Macquarie University and Southern Cross University played a role by employing various techniques to date the samples. Meanwhile, Flinders University provided evidence demonstrating that the sediment within the cave had accumulated in separate layers spanning tens of thousands of years.

  Since its initial excavation and the unearthing of a skull and mandible in 2009, the cave has sparked controversy. The prevailing evidence pertaining to our earliest migrations from Africa to Southeast Asia has typically revolved around island destinations like Sumatra, the Philippines, and Borneo. However, the findings from Tam Pà Ling cave have added a new dimension to the understanding of our early journeys, challenging the conventional notion by highlighting the significance of mainland locations in Southeast Asia.

  Before the revelations of Tam Pà Ling, an elevated cave site situated over 300 kilometers away from the sea in northern Laos, began to unfold, its secrets remained concealed. The identified skull and jawbone were determined to belong to Homo sapiens who had migrated through the area. However, the crucial question remained: When did this migration occur?

  As is usual in questions of human dispersal, the debate comes down to timing. But this evidence was hard to date.

  Due to the protected status of the site as a World Heritage area and the legal restrictions in Laos, direct dating of the human fossils from Tam Pà Ling cave is not feasible. The scarcity of animal bones and suitable cave decorations further complicates the dating process, and the age of the site surpasses the applicability of radiocarbon dating. Consequently, luminescence dating of sediments emerged as the primary method for establishing the chronological framework, bearing the weight of this scientific endeavor.

  
  

  Luminescence dating operates on the principle of a light-sensitive signal that resets to zero upon exposure to light but gradually accumulates over time when shielded from light during burial. Initially, this dating technique was employed to determine the age of the sediment layers that encapsulated the fossils, providing crucial insights into the timeframe of their deposition and preservation.

  "Without luminescence dating, the crucial evidence from Tam Pà Ling would remain devoid of a timeline, and the site would be disregarded in the recognized trajectory of human dispersal through the region," explains Associate Professor Kira Westaway, a geochronologist from Macquarie University. "Fortunately, the versatility of this technique allows it to be adapted to address diverse challenges and shed light on significant discoveries."

  These techniques returned a minimum age of 46,000 years – a chronology in line with the expected timing of Homo sapiens’ arrival in Southeast Asia. But the discovery didn’t end here.

  Between 2010 and 2023, annual excavations, albeit interrupted by three years of lockdowns, progressively unveiled a wealth of evidence substantiating the passage of Homo sapiens through Tam Pà Ling cave on their journey towards Australia. Throughout the process, seven fragments of the human skeleton were discovered at various intervals within a sedimentary depth of 4.5 meters. This remarkable finding pushed the potential timeline significantly back to the earliest migrations of Homo sapiens to this particular region.

  To tackle the challenges posed by the limited dating options, the research team demonstrated ingenuity by employing innovative approaches. They strategically utilized available dating techniques, such as uranium-series dating, to analyze a stalactite tip that had been buried in sediment. Additionally, they combined uranium-series dating with electron-spin-resonance dating techniques to examine two exceptionally rare and intact bovid teeth discovered at a depth of 6.5 meters. These creative applications of various dating methods enabled the team to derive valuable chronological insights and enhance the understanding of the site's history.

  "By directly dating the fossil remains and confirming the chronological sequence established through luminescence dating, we were able to propose a comprehensive and reliable timeline for the presence of Homo sapiens at Tam Pà Ling," states Associate Professor Renaud Joannes-Boyau, a geochronologist from Southern Cross University. This direct dating approach provided a crucial confirmation of the age estimates, solidifying the understanding of the site's history and the presence of our human ancestors within it.

  To bolster the dating evidence, the team conducted a thorough analysis of the sediments, employing micromorphology—a technique that scrutinizes sediments under a microscope to assess the integrity of the layers. This meticulous examination played a crucial role in the new chronology by determining the origin of the fossils. By establishing the consistent accumulation of sedimentary layers over an extended period, this analysis served as a pivotal component in validating the comprehensive timeline of the site's history.

  "Contrary to the notion of a rapid sediment deposition, the site at Tam Pà Ling reveals a consistent and seasonally deposited sequence of sediments," elucidates Associate Professor Mike Morley, a geoarchaeologist from Flinders University. This observation, made in collaboration with PhD students Vito Hernandez and Meghan McAllister-Hayward, emphasizes that the sediments accumulated gradually over time, reflecting a stable and predictable pattern of deposition. This understanding further contributes to the comprehensive picture of the site's formation and adds valuable insights to the study.

  The newly established chronology unveiled an extended human presence in the area spanning over 56,000 years. Notably, the age of the fossil fragment, found at a depth of seven meters and identified as a piece of a leg bone, indicates that modern humans arrived in this region between 86,000 to 68,000 years ago. This remarkable finding pushes back the estimated arrival time in mainland Southeast Asia by approximately 40,000 years. However, genetic studies indicate that these early migrations had a minimal contribution to the genetic makeup of present-day populations.

  Associate Professor Westaway emphasizes the significance of the research, describing it as the definitive paper that solidifies the Tam Pà Ling evidence. The availability of substantial dating evidence finally enables the confident determination of when Homo sapiens initially arrived in the area, their duration of presence, and the potential route they may have taken. This crucial study marks a milestone in understanding the ancient human migrations and sheds light on the history of our species in the region.

  The proximity of Tam Pà Ling cave to the recently discovered Cobra Cave, known to have been inhabited by Denisovans approximately 70,000 years earlier, suggests an intriguing possibility. Despite the previous dearth of evidence for early arrival in mainland Southeast Asia, this region could potentially represent a previously utilized dispersal route among our ancient ancestors, long before the advent of Homo sapiens. This revelation adds an additional layer of complexity to the story of human migrations and highlights the significance of further exploration and research in the area.

        “We have much to learn from the caves and forests of Southeast Asia,” adds Associate Professor Westaway.