Cambodia

Cambodia's Mekong River valley and the fertile basin surrounding Tonle Sap lake preserve some of the earliest traces of human presence in mainland Southeast Asia. Archaeological layers at Laang Spean cave in Battambang province contain Hoabinhian stone tools and faunal remains dating to at least 12,000 years ago, while surface finds and sediment cores elsewhere in the lowlands hint at sporadic occupation extending back toward the end of the Pleistocene. These early foragers belonged to a broad technological tradition shared across much of Southeast Asia and southern China, though the precise genetic affinities of these populations remain poorly resolved because no ancient genomes from Cambodian Pleistocene contexts have yet been published.

By the third millennium BCE, archaeological sequences at sites such as Samrong Sen and the recently excavated mound of Krek 52/62 document the arrival of sedentary villages that cultivated rice and kept domesticated pigs and dogs. Linguistic reconstructions and comparative pottery styles indicate that these communities spoke early Austroasiatic languages, whose spread from the middle Yangtze region or adjacent areas is thought to have carried farming economies southward. The extent to which incoming farmers replaced or merely admixed with local hunter-gatherers continues to be debated; current models favor substantial but incomplete replacement, with residual foraging groups persisting in upland zones for centuries.

Ancient-DNA studies of later prehistoric and early historic individuals from Cambodia and neighboring countries supply direct evidence for this demographic history. Genomes from Bronze and Iron Age contexts in the Mekong region, analyzed in work by Lipson, Reich, and colleagues, show that present-day Khmer derive the majority of their ancestry from Neolithic Austroasiatic-related farmers who carried both East Asian and deeply diverged Southeast Asian hunter-gatherer components. These data also reveal subsequent gene flow from Tai-Kadai and Austronesian sources during the first millennium CE, underscoring that Khmer genetic identity emerged through repeated episodes of mixture rather than from a single founding population.

Between the ninth and fifteenth centuries CE, the Khmer polity centered at Angkor consolidated political and hydraulic control over the Tonle Sap basin, producing the largest religious monument complex in the world. Inscriptions, temple reliefs, and settlement surveys document a multi-ethnic realm whose core population spoke Khmer yet incorporated Mon, Cham, and other groups. The empire’s eventual decline, linked to climatic shifts, overextension of irrigation networks, and shifting trade routes, prompted a southward reorientation of Khmer society toward the Mekong delta, a movement still visible in modern dialect geography.

Cambodia therefore occupies a pivotal position in the broader narrative of human migration and cultural innovation in Southeast Asia. Its archaeological and genetic records illustrate how Pleistocene foragers, Neolithic farmers, and later state-level societies successively shaped the region’s demographic landscape, while also highlighting the limits of current evidence: the absence of securely dated Pleistocene genomes and the need for finer-resolution sampling of Iron Age sites leave important questions about the timing and scale of early population movements unresolved.