When did the first representatives of Homo sapiens come to Southeast Asia? Until now, around 50,000 years ago was considered the most likely time for settlement by our ancestors. But new finds in a cave in northern Laos now push that time back thousands of years. There, scientists have discovered a piece of a skull and a fragment of a tibia that belong to Homo sapiens but have been dated to be more than 70,000 years old. According to the team, this suggests that there were multiple advances by Homo sapiens even before the main wave of our ancestors’ migration to Asia. However, these pioneer populations were apparently not able to survive in the long term.
For a long time it seemed clear that the anatomically modern human only emerged around 200,000 years ago in Africa and spread across the Middle East to Europe and Asia 50,000 to 60,000 years ago. But in recent years, new fossil discoveries have disproved this timeline. 300,000-year-old Homo sapiens relics in Morocco show our species arose earlier than thought. Findings in the Middle East and on the Arabian Peninsula documented the presence of Homo sapiens in this region as early as 120,000 to 180,000 years ago. And in Southeast Asia, too, the picture is becoming increasingly confusing: although genome studies suggest that the first ancestors of today’s inhabitants arrived around 50,000 years ago, teeth of Homo sapiens were discovered in Sumatra that are already around 70,000 years old. Homo sapiens relics dating back 65,000 years have been found in Australia.
Fossil finds in northern Laos
“These findings point to a complex pattern of spread that is difficult to reconcile with the current genetic evidence,” explain Sarah Freidline of the University of Central Florida in Orlando and her colleagues. One possible explanation, however, is that the archaeological finds come from early, unsuccessful forays by Homo sapiens. According to this, the first groups of modern humans could have arrived in Southeast Asia long before the great wave of settlement around 50,000 years ago, but they were not able to stay there permanently. These pioneer populations died out again. The same is assumed for the colonization of Europe by Homo sapiens. New finds and dates from the Tam Pà Ling Cave in northern Laos now provide further evidence for this “pioneer” theory. In 2009, several bones of early Homo sapiens were discovered in this cave, located in the highlands about 300 kilometers from the nearest coast.
However, dating these relics proved difficult because conventional methods such as radiocarbon or uranium-lead dating were not possible. The only clue was a dating of the sediment using the luminescence method. It can be used to determine when a mineral was last exposed to light from the soil surface. According to the dating at that time, the find layer of the human relics named TPL-1 to TPL-5 came from more than 46,000 years ago. Since then, however, the research team has continued to excavate the cave, uncovering two more human fossils in two deeper layers. The TPL-6 find is a fragment of the front left side of the skull, while TPL-7 is part of a tibia. According to comparative analyses, both bone fragments come from a Homo sapiens. “The clear affinities of the TPL fossils for Homo sapiens suggest that these people descended from a petite population of Homo sapiens, either in Africa, the Middle East, or locally,” write Freidline and her colleagues.
“Pioneer” groups arrived well over 70,000 years ago
The new fossils and closer analysis of the strata also allowed the team to more accurately date them using luminescence and two uranium-lead assays. The result: “The dates consistently show that the oldest fossils from Tam Pà Ling are between 95,000 and 65,000 years old,” the researchers report. “These fossils thus represent some of the oldest diagnosable craniomandibular relics of Homo sapiens in Southeast Asia. According to the scientists, these finds and their dating support the assumption that there were early, probably unsuccessful advances of Homo sapiens from Africa and the Middle East to Southeast Asia more than 70,000 years ago. “The delicate expression of the TPL-6 cranial bone suggests that this human descended from a population of graceful immigrants and was not the result of local evolution or mixing of Homo erectus and Denisovans,” they explain. This sheds new light on the early history of Southeast Asia and the early movements of Homo sapiens.
“Based on these finds as well as the fossils of Homo erectus, Homo floresiensis and Homo luzonensis and a Denisova tooth from northern Laos, Southeast Asia is thus revealed to be a region that had a rich diversity of members of the genus Homo in the middle to late Pleistocene,” write Freidline and her colleagues. The location of Tam Pà Ling Cave far from the coast also suggests, in their view, that early members of our species not only spread along the coasts of Southeast Asia, but also roamed the forested areas inland. “We still have a lot to learn from the caves and forests of Southeast Asia,” says co-author Kira Westaway of Macquarie University in Sydney.
Source: Sarah Freidline (University of Central Florida, Orlando) et al., Nature Communications, doi: 10.1038/s41467-023-38715-y