Deciduous and evergreen forests dominate the limestone karst formations in the northwestern highlands of Thailand. The mountains are dotted with a large number of caves and rock shelters. In more than 40 such caves in Mae Hong Son Province, large wooden coffins can be found mounted on stilts, dating back to between 2,300 and 1,000 years ago. During the Iron Age period, each of these several-metre-long coffins was made from a single teak tree and features fine carvings of geometric, animal or human shapes at 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 of the Highland Pang Mafa Project, led by Professor Rasmi Chokongdig, from the Department of Archaeology, Faculty of Archaeology, Silpakorn University. “Our research addresses the relationship between humans and their environments in the monsoon tropics. A crucial aspect is exploring the social structure of these prehistoric societies, as well as explaining their connections with pre-Neolithic, Neolithic and post-Neolithic groups in this region,” she added. says Rasmi Şükonjed, archaeologist and senior author of the study.
To understand the genetic profile of communities associated with wooden coffins, and the connectivity between individuals buried in different caves, a multidisciplinary team of researchers from Germany and Thailand analyzed the DNA of 33 ancient individuals from five wooden coffin sites. Genomes recovered from ancient individuals allow the first detailed study of the structure of prehistoric society from Southeast Asia. “This project demonstrates how ancient DNA can contribute to our understanding of past societies, their daily lives, and their connections across regions,” says first author Selina Karlhoff, a researcher in the Department of Archaeogenetics at the Max Planck Institute for Evolution. anthropologist.
The complex genetic landscape in post-Neolithic Southeast Asia
DNA preservation conditions in the tropics are challenging and limit ancient population genetic studies from Southeast Asia. Most studies have been limited to single individuals or small groups representing a particular country and time period, and have identified only broad patterns, such as the genetic admixture of farmers from the Yangtze River Valley in southern China with the local gene pool associated with hunter-gatherers during the pre-Paleolithic period. -New Stone Age. The current study identifies two separate farmer-associated lineages in individuals associated with Log Coffin. One is connected to the Yangtze River Valley and the other to the Yellow River Valley in China. While previously published individuals from Myanmar, Laos and Vietnam also bear ancestry linked to the Yellow River, 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 funerary practices and diet, and indicate separate spheres of influence and contacts for separate primary migration routes during the Neolithic.
“Our results contribute to the emerging picture of the complex genetic landscape in mainland Southeast Asia post-Neolithic. However, this study provides successful genetic results from samples in limestone caves from the northwestern highlands of Thailand. Future studies of samples recovered from the open air,” he says. Weibo Kuttanan, a scientist from Naresuan University in Thailand, co-author of this study: “The archaeological sites in the lowlands look promising. “If possible, they could provide additional insight into the genetic history of mainland Southeast Asia.” Detailed analyzes of monomarkers, which could reveal sex-specific demographic histories of groups associated with Log Coffin, will be provided in a forthcoming study. Further archaeological studies are warranted Collaboration with local scientists, combined with new mixture modeling and dating techniques, will better highlight developing patterns and enable direct communication of archaeological findings and hypotheses.
The first community-level analysis in Southeast Asian archaeology
At the local level, the study provides 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. Analysis of so-called IBD (identical by descent) blocks helps trace complex biological association patterns within a site and across regions – and has not yet been applied in archaeological studies in Southeast Asia. The study identified genetic relatives buried in the same cave system, such as fathers and sons or grandparents and grandchildren. This group of closely related individuals was more distantly related to all other individuals buried at the site.
While this suggests burial place was chosen with genetic relatedness in mind, the more distant genetic relationships between Log Coffin sites, a low level of blood consanguinity, as well as high mitochondrial and low genome-wide diversity suggest that groups associated with Log Coffin were Fairly large and constantly connected to each other via different river valleys. “This finding is very important, as wooden coffins were also used in other archaeological cultures throughout Southeast Asia. Comparing linkage patterns and genetic links across regional regions will be a great collaborative project in the future that can explain cultural dynamics and population interactions in Southeast Asia.” Asian and others,” says Rasmi Çokongdej.
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