Both genetic and fossil evidence suggests that Modern Humans emerged in Africa about 300 000 years ago. The timing of subsequent dispersals into Eurasia, however, is much less well defined, with numerous models having emerged, which nevertheless can be split into two broad groups; an early dispersal during Marine Isotope Stage 5 (roughly 130 000-80 000 years ago), and a late dispersal, after Marine Isotope Stage 5. Most genetic evidence supports the ancestors of all modern non-African populations having left the continent between 50 000 and 60 000 years ago, and subsequently diverged from one-another, with some groups moving east into Asia and others west into Europe. There is, however, some genetic evidence supporting the idea that modern Australasians are at least partly descendent from a Modern Human population which left Africa earlier, although the DNA of this group makes up less than 1% of that of modern Austrolasian populations.
A number of sites in the Middle East and around the eastern Mediterranean Basin have yielded fossils considered to be Modern Humans, dating to between 210 000 and 90 000 years ago, supporting the idea of an early dispersal at least a small way out of Africa. There are also a number of fossils from China, which have been considered to Modern Humans between 127 000 and 70 000 years old, although recent re-examination of these has shown that all suffer with problems with their dating and/or their assignment to Modern Humans. Further south, material attributed to Modern Humans at Lida Ajur in Sumatra has been dated to 73 000-63 000 years before the present, and at Tam Pà Ling in northern Laos has been dated to 70 000-46 000 years before the present, while Madjedbebe, the oldest archaeological site in Australia (which only Modern Humans are thought to have reached), has been dated to 65 000 years before the present. It these findings are correct, then they apparently represent an older Human excursion into Southeast Asia and beyond, possibly by a group with no living ancestors.
In a paper published in the journal Nature Communications on 13 June 2023, a team of archaeologists led by Sarah Freidline of the Department of Anthropology at the University of Central Florida, and the Department of Human Origins at the Max Planck Institute for Evolutionary Anthropology, describe new fossil material from Tam Pà Ling site, and provide an updated chronology for the site.
The Tam Pà Ling site was discovered in 2009, when a partial cranium (TPL 1) was unearthed in a cave on the Pà Hang karstic tower, on the southeasterd flank of P’ou Loi Mountain, in Houaphanh Province, northeastern Laos. Further excavations yielded two mandibles (TPL 2 & TPL 3), a rib (TPL 4), a phalanx (TPL 5), and most recently a partial frontal bone (TPL 6) and tibia (TPL 7), which Freidline et al. describe for the first time.
A combination of radiocarbon and uranium series dating has been used to date the previous finds from Tam Pà Ling, establishing a chronological sequence in which the first discovered skull (TPL 1) and mandible (TPL 2), both from the upper 25 cm of sediment, are about 46 000-years-old. Two soil samples collected from depths of 4.0 m and 5.0 m yielded dates of 48 000 years before the present. This short time interval/large increase in depth combination has caused questions to be asked about the accuracy of the dating methods used.
Sedimentation in the Tam Pà Ling cave is thought to have been linked to the annual monsoon cycle, with contiguous fine-grained layers across the site and no sign of secondary disturbance. The cave is thought to have opened gradually, during a period of drier conditions during which slabs of limestone fell from the cave roof, and the fine sediments being deposited onto these. The South Asian Monsoon is believed to have been continuous since Marine Isotope Stage 5, giving a minimum age for this dry period. Freidline et al. used a combination of dating techniques to obtain new dates for strata below 5.0 m within Tam Pà Ling cave, extending the age range to 7.0 m and an age of 86 000 years.
Next, Freidline et al. carried out a morphometric analysis, comparing the Tam Pà Ling fossils to similar bones from a selection of other Humans and Hominins.
TPL 6 is a partial left frontal bone that is broken at one-third of its total length and shows a fracture on its upper right side. A principal component analysis of its shape placed it firmly among Modern Human specimens from the Holocene and Late Pleistocene, including the Minatogawa individuals from Okinawa, Japan, which are dated to between 22 000 and 20 000 years ago, the Zhoukoudian Upper Cave individuals, from Beijing, China, dated to between 20 000 and 10 000 years ago, and the Wadjak (37 000-28 000-years-old), and Lake Mungo individuals (about 40 000 years old) of Australia, the Salkhit individual (34 950-33 900-years-old) from Mongolia, and Holocene Individuals from Southeast Asia.
The previously described skull, TPL 1, is larger and more robust that TPL 6, but also plots with Late Pleistocene and Holocene Modern Humans. This more complete skull has a maxilla (upper jaw), a highly distinctive feature for separating Neanderthals, early Modern Humans, and later Modern Humans, with this feature clearly grouping with later Modern Humans such as Liujiang Man, from Guangxi in China, dated to between 159 000 and 60 000 years before the present (although these dates have been questioned), the Zhoukoudian Upper Cave individuals, and Laetoli Hominin 18, about 120 000-years-old from Kenya. The subnasal region of this skull is sloping and its palate broad, also Modern Human traits, with the shape of these features placing TPL 1 close to the Qafzeh 6 individual, about 100 000-years old, from Israel, Liujiang Man, and a number of Late Pleistocene and Holocene specimens. Other features of this skull fall within the overlap of early and later Modern Human morphologies.
The first of the two isolated mandibles found at Tam Pà Ling cave, TPL 2, was found to map with Late Pleistocene and Holocene Modern Humans, being closest to the Tianyuandong individual, from Zhoukoudian and dated to between 42 000 and 39 000 years before the present. and the Tam Hang South individuals, from northern Laos and dated to about 15 700 years before the present.
The second isolated mandible, TPL 3 has a pronounced chin (a feature unique to Modern Humans), and is morphologically most similar to Late Pleistocene Humans, such as the Zhoukoudian Upper Cave individuals, and the Minatogawa individuals.
Freidline et al.'s new data extends the known Human presence at Tam Pà Ling cave 10 000 years further into the past, increasing the known period of residence to about 56 000 years. The new specimens, frontal TPL 6 and tibia TPL7, indicate that Modern Humans have been present in Southeast Asia for at least 68 000 years. These skeletons are of a gracile (slender) type, inconsistent with more archaic Human types, though it is unclear if their ancestors were recent arrivals from Africa or the Middle East, or were part of an unknown local population. The earliest known Modern Humans in Asia are found at Misliya Cave in Israel, and are dated to between 194 000 and 179 000 years before the present, with a number of slightly younger sites known from elsewhere in the Middle East, but the main Modern Human expansion into Asia seems not to have happened till about 65 000-45 000 years ago, when almost all non-African populations rapidly distributed across the Eurasian landmass. The oldest known Human genomes all date to between 45 000 and 35 000 years before the present. Available genetic data from Southeast Asia is much more recent, but shows that a hunter-gatherer population was largely replaced by an incoming farming population about 4000 years ago, although both of these populations seem to have been part of the rapid expansion from Africa 45 000-35 000 years ago. The later fossils from Tam Pà Ling cave fall within the range of this rapid expansion phase, but the new material, TPL 6 and TPL 7, are much older, dated to between 73 000 and 67 000 years before the present. This raises two possibilities; either the Tam Pà Ling fossils represent an older, Human dispersal into Southeast Asia, which has not contributed to the DNA of living Humans, or they represent part of an older successful Human migration into Asia, which has contributed to the DNA of living Humans, but which has not previously been identified. Unfortunately, attempts to recover DNA from the molars of TPL 1 and TPL 3 were unsuccessful, leaving the question unanswered at this time.
Morphometric analysis of the specimens, identifies them firmly as Modern Humans, being close in form to a number of Late Pleistocene individuals from East Asia, notably Zhoukoudian Upper Cave 101, from Beijing (China), Minatogawa 2, from Okinawa (Japan), Liujiang Man, from Gunagxi (China), Tabon Man, from Palawan (Philippins), and Tianyuandong 1, also from Beijing. The Tam Pà Ling individuals show quite a lot of variation, something previously recorded in the Zhoukoudian Upper Cave and Minatogawa populations, and supporting the hypothesis that these Late Pleistocene populations were quite heterogeneous. The frontal bone TPL 6 and mandible TPL 2 are notably slender, more so than any other specimens in the database, with the exception of the (much smaller) Homo floriensis fossils. The partial cranium, TPL 1, and second mandible, TPL 3, are more robust, falling within the general range of Late Pleistocene populations. Curiously, the later fossils appear more robust than the gracile early frontal TPL 6, against a general tendency for more modern Homo sapiens to be more gracile, while more archaic forms are more robust. If their is a line of decent through these fossils, then this suggests that the more robust traits were acquired locally through genetic drift or as an adaptation to local conditions, challenging the assumption made in other parts of the Eurasia that the appearance of more robust features is a sign of interbreeding with more archaic populations.
The TPL 6 frontal is closest in form to Minatogawa 2, another frontal from Okinawa in Japan, dated to about 20 000 years before the present. Of the three sets of remains at Minatogawa, the more complete skeleton, Minatogawa 1, is more robust, and considered to be male, while the two more fragmentary sets of remains, frontal Minatogawa 2 and mandible Minatogawa 3, are more gracile and thought to be female. Collectively, these individuals have been suggested to be closer to southern Australo-Melanesian populations than to more northern, Asian populations, along with other fossils from Liujiang, in Guangxi, South China, Niah Cave, in Sarawak, Malaysian Borneo, and Wadjak, East Java. The differences in size and robustness between TPL 1 and TPL 6 are similar to those between Minatogawa 1 and Minatogawa 2, though while the latter two are thought to be roughly contemporary, TPL 1 and TPL 6 are thought to be separated by about 30 000 years. The differences between the remains could, therefore, represent sexual dimorphism, changes in the stature of the population over time, or interbreeding with members of a more robust Human population. It is also possible that the assessment of TPL 6 as an adult is incorrect, and that this individual was in fact an adolescent member of a population with a slightly different development than living Humans. Nevertheless, Freidline et al. believe that the similarity of TPL 6 to later remains from Tam Pà Ling combined with the absence of any evidence of genetic continuity from Marine Isotope Stage 5 to the current day in Asia, means that the most likely explanation is that the Tam Pà Ling population comprises members of an earlier Human expansion into Southeast Asia, which has left no survivors. The oldest Human remains in Southeast Asia from which DNA has been extracted, the 7800-year-old remains from Pha Faen, also in Laos, produced no genetic evidence of descent from an earlier dispersal.
The second oldest fossil form Tam Pà Ling is the partial mandible, TPL 3, which has been dated to about 70 000 years before the present, and which a previous morphometric analysis placed close to Pleistocene Archaic Humans, including Neanderthals and Middle Pleistocene Hominins, but outside the range of even early Modern Humans. this was due to a wide bi-mental breadth (i.e. the breadth of the front of the jaw), which is in turn associated with a wide ramus (the hinge which connects the lower jaw to the skull), a feature associated with Archaic Humans. However, TPL 3 has a well-developed chin, a feature otherwise exclusively associated with Modern Humans.
The Zhiren 3 mandibular corpus, from Guangxi in South China, which has been dated to about 100 000 years ago (although this date has recently been challenged), also has a combination of a large width and a chin (albeit less well developed than in TPL 3), combined with an apparently modern dentition. This specimen has been suggested to possibly represent a hybridization between early dispersing Modern Humans and a local Archaic Human population. Freidline et al.'s study suggests that there is a considerable overlap in shape between the anterior symphysis of the mandible in Modern Humans and Neanderthals, while other Archaic Humans, including Homo erectus, Homo floriensis, and Denisovans, have more distinct shapes. Zhiren 3 is more archaic in its structure than TPL 3, but both are decidedly more modern than the Denisovan Xiahe mandible, which is very robust, lacks a chin, and has a receding symphysis. Neither Zhiren 3 nor TPL 3 show any affinity to the Xiahe mandible; both are more similar to the mosaic structures of early Modern Humans from Africa. Zhiren 3 appears most similar to specimens from Minatogawa, Zhoukoudian Upper Cave, and Border Cave in South Africa. It is also small, a feature shared with the Minatogawa, Zhoukoudian Upper Cave, Border Cave, and Tam Pà Ling remains, as well as the Klasies River Mouth remains (also South Africa). This suggests that Zhiren 3 could either represent a member of an early, unsuccessful dispersal of Modern Humans into Asia, or one of the earliest members of a late dispersal.
The TPL 2 mandible is younger, smaller, and in some ways morphologically more modern than TPL 3. Despite this it has a notably robust lateral corpus, more so than seen in Homo erectus skulls, although all other features point to it being a Modern Human jaw. Notably, TPL 2 is small, smaller than any other apparently adult mandible in Freidline et al.'s study, with the exception of one assigned to Homo floriensis. Morphologically, TPL 2 is closest to mandibles from the Tam Hang Rockshelter (northern Laos) thought to be from young adult women, and dated to about 15 700 years ago. These individuals are estimated to have been between 140 cm and 153 cm tall, which is short by modern Western standards, but not exceptionally so, and is also comparable to the Minatogawa individuals, and many Holocene populations from East and Southeast Asia. Notably, among living and recent Humans, populations with short statures are often found in tropical forests, and the Late Pleistocene environment at Tam Pà Ling has been reconstructed as a tropical forest, much as it is today. Furthermore, a study of carbon isotopes from two of the teeth of TPL 1 suggested that that individual had forest-associated diet.
TPL 1 was found in the same layer as TPL 2, with both being dated to between 52 000 and 40 000 years ago. TPL 1 resembles other Late Pleistocene Modern Humans from Asia, notably the Zhoukoudian Upper Cave and Palawan individuals. The Zhoukoudian Upper Cave individuals have been suggested to show affinities with Upper Palaeolithic individuals from Europe, and earlier Modern Humans from Africa and the Levant, and appear to have retained some archaic traits rather than acquired them by interbreeding with a more archaic population.
The fossils from Tam Pà Ling give an insight into Human variability during the Late Pleistocene of Southeast Asia. The site shows a Human presence in the region between 86 000 and 42 000 years ago, including the oldest confidently assigned Modern Human cranial remains in Southeast Asia. The TPL 6 frontal bone shows a dispersal into Southeast Asia by a Modern Human population by 70 000 years ago, although it is by no means certain that this population has living descendants. This cranial has a remarkably slender form, making it highly probable that it is a representative of a group migrating into the area for the first time, and highly unlikely that it is descended from or admixed with a local Archaic Human population. These fossils add to our understanding of a region which appears to have had a rich and diverse Human and Hominin population during the Middle and Late Pleistocene, including Homo erectus, Homo floriensis, Homo luzonensis, Denisovans, and Modern Humans.
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