A multi-proxy approach to exploring Homo sapiens’ arrival, environments and adaptations in Southeast Asia

The capability of Pleistocene hominins to successfully adapt to different types of tropical forested environments has long been debated. In order to investigate environmental changes in Southeast Asia during a critical period for the turnover of hominin species, we analysed palaeoenvironmental proxies from five late Middle to Late Pleistocene faunas. Human teeth discoveries have been reported at Duoi U’Oi, Vietnam (70–60 ka) and Nam Lot, Laos (86–72 ka). However, the use of palaeoproteomics allowed us to discard the latter, and, to date, no human remains older than ~ 70 ka are documented in the area. Our findings indicate that tropical rainforests were highly sensitive to climatic changes over that period, with significant fluctuations of the canopy forests. Locally, large-bodied faunas were resilient to these fluctuations until the cooling period of the Marine Isotope Stage 4 (MIS 4; 74–59 ka) that transformed the overall biotope. Then, under strong selective pressures, populations with new phenotypic characteristics emerged while some other species disappeared. We argue that this climate-driven shift offered new foraging opportunities for hominins in a novel rainforest environment and was most likely a key factor in the settlement and dispersal of our species during MIS 4 in SE Asia

Environmental conditions framing the first evidence of modern humans at Tam Pà Ling, Laos: A stable isotope record from terrestrial gastropod carbonates

Mainland Southeast Asia is a key region to interpret modern human migrations; however, due to a scarcity of terrestrial proxies, environmental conditions are not well understood. This study focuses on the Tam Pà Ling cave site in northeast Laos, which contains the oldest evidence for modern humans in Indochina, dating back to MIS 4 (70 ± 8 ka). Snail remains of Camaena massiei found throughout the stratigraphic sequence contain a valuable oxygen and carbon isotope record of past local vegetation and humidity changes. Our data indicate that before the Last Glacial Maximum (LGM), northeast Laos was characterized by a humid climate and forested environments. With the onset of the LGM, a major climatic shift occurred, inducing a sharp decrease in precipitation and a significant decline in woodland habitats in favor of the expansion to more open landscapes. Only during the Holocene did forests return in northeast Laos, resembling present conditions. The first Homo sapiens arriving in Indochina therefore encountered landscapes dominated by woodlands with a minor proportion of open habitats

Trophic ecology of a Late Pleistocene early modern human from tropical Southeast Asia inferred from zinc isotopes

Tam Pà Ling, a cave site in northeastern Laos, has yielded the earliest skeletal evidence of Homo sapiens in mainland Southeast Asia. The reliance of Pleistocene humans in rainforest settings on plant or animal resources is still largely unstudied, mainly due to poor collagen preservation in fossils from tropical environments precluding stable nitrogen isotope analysis, the classical trophic level proxy. However, isotopic ratios of zinc (Zn) in bioapatite constitute a promising proxy to infer trophic and dietary information from fossil vertebrates, even under adverse tropical taphonomic conditions. Here, we analyzed the zinc isotope composition (66Zn/64Zn expressed as δ66Zn value) in the enamel of two teeth of the Late Pleistocene (63–46 ka) H. sapiens individual (TPL1) from Tam Pà Ling, as well as 76 mammal teeth from the same site and the nearby Nam Lot cave. The human individual exhibits relatively low enamel δ66Zn values (+0.24‰) consistent with an omnivorous diet, suggesting a dietary reliance on both plant and animal matter. These findings offer direct evidence of the broad utilization of resources from tropical rainforests by one of the earliest known anatomically modern humans in Southeast Asia