March 1, 2024

The genetic footprint of Thailand’s lost civilizations revealed in Iron Age log coffins

Caves and rock shelters dot the mountains in the northwestern highlands of Thailand. More than 40 in Mae Hong Son Province contain wooden coffins on stilts, dating back 1,000 to 2,300 years. Credit: © Selina Carlhoff

Ancestral Iron Age log coffin culture in Thailand

Deciduous and evergreen forests dominate the limestone karst formations of the northwestern Thai highlands. A large number of caves and rock shelters intersperse the mountains. In more than 40 of these caves in Mae Hong Son province, large wooden coffins mounted on stilts can be found, dating between 2,300 and 1,000 years ago. During the Iron Age period, each of these several meter long coffins was made from a single teak tree and features refined carvings of geometric, animal or human shapes on the handles at both ends.

This archaeological assemblage has been studied for more than two decades by members of the Prehistoric Population and Cultural Dynamics Project in Highland Pang Mapha, led by Professor Rasmi Shoocongdej, Department of Archeology, Faculty of Archeology, Silpakorn University.

“Our research examines the relationship between humans and their environments in the seasonal tropics. A crucial aspect is exploring the social structure of these prehistoric communities, as well as explaining their connections with other pre-Neolithic, Neolithic and post-Neolithic groups in this region”, says Rasmi Shoocongdej, archaeologist and senior author of the study.

Iron Age log coffin culture in Thailand

In the Iron Age log coffin culture of Thailand, coffins were made from a single teak tree and decorated with exquisite carvings of geometric or animal shapes on both ends. Credit: © Selina Carlhoff

To understand the genetic profile of communities associated with Log Coffin and the connection of individuals buried in different caves, an interdisciplinary team of researchers from Germany and Thailand analyzed the DNA of 33 ancient individuals from five Log Coffin sites. Genomes recovered from ancient individuals enable the first detailed study of the structure of a prehistoric Southeast Asian community.

“This project illustrates how ancient DNA can contribute to our understanding of past communities, their daily lives and their interregional connections,” says first author Selina Carlhoff, researcher in the Department of Archaeogenetics at the Max Planck Institute for Evolutionary Anthropology. .

Complex genetic landscape on the post-Neolithic continent of Southeast Asia

DNA preservation conditions in tropical regions are challenging and limit genetic studies of ancient Southeast Asian populations. Most studies have been limited to single individuals or small groups representing a country and period, and identifying only broad patterns, such as genetic admixture of farmers from the Yangtze River valley in southern China with the local Hòabìnhian gene pool associated with hunter-gatherer during the pre-Neolithic period.

The present study identifies two separate farmer-associated ancestors in the individuals associated with the Log Coffin. One connected to the Yangtze River Valley and the other to the Yellow River Valley in China. Although previously published individuals from Myanmar, Laos, and Vietnam also have Yellow River-related ancestry, it was absent in Bronze and Iron Age individuals from Ban Chiang in northeastern Thailand. These genetic differences reflect cultural differences between the two regions, such as mortuary practices and diet, and point to separate spheres of influence and links to separate early migration routes during the Neolithic period.

“Our results contribute to the emerging picture of a complex genetic landscape in post-Neolithic mainland Southeast Asia; however, this studyprovides successful genetic results from samples in limestone caves of the northwestern highlands of Thailand. Future studies of samples recovered from lowland open-air archaeological sites appear promising. If possible, they could provide additional information about the genetic history of mainland Southeast Asia.”, says Wibhu Kutanan, a scientist at Naresuan University in Thailand, involved in designing the study.

Detailed analyzes of uniparental markers, which can reveal sex-specific demographic histories of groups associated with the Log Coffin, will be provided in an upcoming study. Further archaeogenetic studies in collaboration with local scholars, as well as new admixture modeling and dating techniques, will better illuminate developing patterns and allow direct connections to archaeological discoveries and hypotheses.

First community-level analysis in Southeast Asian archeology

At the local scale, the study provided the first community-level analysis in Southeast Asian archaeology. To investigate relationships between individuals, the authors used identical genetic regions in two individuals because they were inherited from a common ancestor. The analysis of so-called IBD blocks (identical by descent) helps trace complex patterns of biological relatedness within a site and between regions – and until now has not been applied in archaeogenetic studies of Southeast Asia.

The study identified close genetic relatives buried in the same cave system, such as parents and children or grandparents and grandchildren. This cluster of closely related individuals was most distantly connected to all other individuals buried at the site.

Although this suggests burial site selection taking into account genetic relatedness, the more distant genetic relationships between Log Coffin sites, a low level of inbreeding, as well as high mitochondrial diversity and low genomic diversity suggest that groups associated with the Log Coffin were quite large and constantly connected to each other through different river valleys.

“This result is highly significant, as wooden coffins were also used in other archaeological cultures throughout Southeast Asia. Comparing kinship patterns and interregional genetic connections would be a fascinating future collaborative project that could explain cultural dynamics and population interactions in Southeast Asia and other regions,” says Rasmi Shoocongdej.

Reference: “Genomic portrait and relationship patterns of the Iron Age log coffin culture in northwestern Thailand” by Selina Carlhoff, Wibhu Kutanan, Adam B. Rohrlach, Cosimo Posth, Mark Stoneking, Kathrin Nägele, Rasmi Shoocongdej, and Johannes Krause , December 22, 2023,

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