From Mosaic Environments to Closed Forests: Dietary Adaptations of Hoabinhian Hunter-Gatherers in Northwestern Thailand Across the Pleistocene – Holocene Transition

Kantapon Suraprasit1*, Rasmi Shoocongdej2,3, Athiwat Wattanapituksakul3, Kanoknart Chintakanon3, and Hervé Bocherens4

Ongoing archaeological and paleoanthropological research has improved our understanding of how environmental change influenced early human and large mammal adaptations in tropical Southeast Asia, although the precise context of human arrival in the region remains unresolved due to challenges related to site preservation, chronological control, and correlation between archaeological and paleoenvironmental records. Here, we have investigated two archaeological sites in the highlands of Pang Mapha, Mae Hong Son Province, northwestern Thailand: the late Pleistocene Tham Lod Rockshelter and the early to mid-Holocene Ban Rai Rockshelter, both associated with the Hoabinhian technocomplex and yielding abundant human and faunal remains. To investigate the timing of dietary shifts and ecological adaptations among Hoabinhian hunter-gatherers and associated mammals during the Pleistocene–Holocene transition, we analysed stable carbon isotope compositions of human and faunal tooth enamel dated between 34,000 and 5,000 cal yr BP. Stable carbon isotope compositions of human and mammal tooth enamel samples from Tham Lod Rockshelter suggested an expansion of mosaic forest–grassland environments during the terminal Pleistocene, thereby facilitating more opportunistic foraging strategies and broader resource exploitation among Hoabinhian hunter-gatherers. In contrast, the isotope samples from Ban Rai Rockshelter revealed a shift toward greater reliance on C₃ resources among early Holocene hunter-gatherers and some large mammals. When integrated with regional paleoclimatic proxies, these results suggest that dietary changes during the Pleistocene – Holocene transition reflect increasingly homogeneous, closed-canopy forests and wetter climatic conditions. Compared with neighbouring regions, our findings indicate a relatively late emergence of specialised rainforest hunter-gatherers in mainland Southeast Asia.