Yappa Nhae: Log Coffins of the Thai Iron Age

The Yappa Nhae log-coffin assemblage, recovered from two adjacent burial loci (Yappa Nhae 1 and 2) in Mae Hong Son Province, dates to the early Iron Age (radiocarbon-calibrated contexts ~200–450 CE). Archaeological data indicate a distinct mortuary expression: single and multiple interments placed within hollowed log coffins, often accompanied by iron tools and ceramic vessels. These burials sit within a broader tapestry of Mainland Southeast Asian Iron Age societies that combined local hunter-forager traditions with expanding metallurgical technologies.

Material culture at Yappa Nhae shows affinities with highland and riverine networks that cross what is today northern Thailand and adjacent Shan and Lao areas. Limited evidence suggests these communities organized ritual life around the cave and valley landscapes, using durable wooden coffins that both preserved and signalled social memory. Chronology and stratigraphic relations indicate the log-coffin practice at Yappa Nhae developed locally during the first centuries CE, likely building on earlier Bronze Age and late Neolithic settlement and exchange patterns.

Archaeological interpretations remain circumspect: preservation biases in wooden structures and the patchy recovery of grave goods limit fine-grained reconstructions of social hierarchy and long-distance exchange. Still, combined osteological and material analyses point to a community negotiating new technologies and regional connections at the threshold of the historical era.

Twenty-eight human remains from Yappa Nhae (both loci combined) yielded genome and uniparental-marker data that illuminate population history at a local scale. The male (Y-chromosome) profile is heterogeneous: haplogroup F (4 individuals) is the most frequent, followed by CTS (3), Z (3), and isolated cases of M and Y. Haplogroup F is an ancestral node for many non-African Y-lineages and its presence in Southeast Asia is expected; CTS and Z point to deeper east–west structure and possible northern connections. The diversity of Y-lineages suggests multiple paternal ancestries coexisted in this community rather than a single paternal founder event.

Mitochondrial diversity is also high: lineages M (6), F (5), F1f (4), N8* (3) and D (2) predominate. This maternal repertoire is characteristic of Mainland Southeast Asia and southern China, with F1f and N8* potentially reflecting regional sublineages that persisted into the Iron Age. Taken together, the uniparental markers portray a community with deep local roots enriched by contact with neighboring highland and riverine groups.

Because the dataset comprises 28 samples, interpretations are meaningful at the community level but still preliminary for wider demographic modeling. Genome-wide analyses (when available) will better resolve admixture timing and proportions. For now, archaeological context plus uniparental diversity indicate continuity with earlier Southeast Asian populations alongside episodic gene flow from adjacent regions.