Why Did Ancient People Create the Plain of Jars in Laos?/info


Introduction

The Plain of Jars is an extensive megalithic landscape in the Xiangkhouang Plateau of northeastern Laos, comprising more than 90 identified sites containing thousands of large stone vessels — the "jars" — ranging from less than one metre to approximately three metres in height and weighing up to several tonnes. The jars are carved from sandstone, granite, conglomerate, and calcified coral, and are distributed across a high-altitude plateau (approximately 1,000–1,200 metres elevation) that would have offered strategic views and access to important trade routes linking the Mekong and Vietnamese lowlands. The sites were inscribed on the UNESCO World Heritage List in 2019.

Despite more than a century of archaeological attention, beginning with the French colonial-era research of Madeleine Colani in the 1930s, the people who created the jars, the techniques they used, and the precise purpose the vessels served remain poorly understood. The prevalent interpretation is funerary: many jars contain or are associated with human burials, cremation remains, and grave goods. However, the manufacturing process, the reasons for the enormous variation in jar size, and the broader cultural and economic context of the jar-making tradition remain subjects of active investigation.

The archaeological study of the Plain of Jars has been severely constrained by the legacy of the Second Indochina War (1964–1973), during which the Xiangkhouang Plateau was one of the most heavily bombed regions on earth. Unexploded ordnance (UXO) blankets the landscape, making fieldwork dangerous and restricting access to many sites. The ongoing process of UXO clearance is gradually opening new areas for investigation.

What we know

The jars are manufactured from locally available stone — primarily sandstone and granite — quarried from outcrops in the surrounding hills. The carving technique involved pecking and grinding the interior and exterior surfaces with stone tools, though the assumption that iron chisels were used has not been conclusively demonstrated. No conclusive evidence for the specific tools employed in jar manufacture has been recovered, representing a significant gap in understanding the technology of production.

Madeleine Colani's pioneering research in the 1930s produced the first systematic documentation of the jar sites. Working under the auspices of the École française d'Extrême-Orient, Colani mapped major sites, excavated in and around numerous jars, and recovered human remains, bronze and iron artefacts, glass beads, and ceramics. She proposed a funerary interpretation based on the association of jars with human skeletal remains and cremation deposits, and suggested dates ranging from approximately 500 BCE to 500 CE.

More recent investigations by the Lao-Australian team led by Dougald O'Reilly and Louise Shewan, beginning in 2016, have substantially expanded the archaeological record. Their work has documented previously unknown sites, conducted systematic survey and excavation using modern methods, and applied radiocarbon dating and OSL (optically stimulated luminescence) dating to establish a chronological framework. The results suggest that jar manufacture and associated burial practices span from approximately the late first millennium BCE through the early first millennium CE, broadly consistent with Colani's estimates.

The funerary function of the jars is supported by the recurring association of jars with human remains — both primary inhumations and secondary cremation deposits. However, not all jars contain burials, and some sites show evidence of multiple phases of use, suggesting that the jars may have served as ossuaries, charnel vessels, or markers within a broader funerary landscape. Stone disks, interpreted as lids, have been found near some jars, supporting the interpretation that the vessels were originally sealed.

The distribution of jar sites across the Xiangkhouang Plateau suggests a relationship with regional trade networks. The plateau occupies a strategic position between the Mekong lowlands to the west and the Vietnamese coastal lowlands to the east, and the presence of glass beads and exotic materials in jar-associated deposits indicates connections to long-distance exchange networks. Some researchers have proposed that the jar sites functioned as nodes in a trade network, with the jars serving as markers of territorial control, community identity, or elite status.

The cultural identity of the jar makers remains uncertain. No written records survive from the jar-producing period, and the oral traditions of the present-day inhabitants of the plateau (primarily Hmong and Tai-Lao peoples) do not preserve clear memories of the jar tradition, which appears to predate their arrival in the region. The jar makers may have been speakers of Mon-Khmer languages — ancestors of present-day Khmu or related groups — but this identification is speculative.

Classification of theories

A. Plausible explanations (supported by evidence, not refuted):

  1. Funerary monuments. The association of jars with human remains (both inhumation and cremation) supports their use as burial vessels, ossuaries, or components of a mortuary landscape. This is the dominant interpretation.
  1. Secondary burial or exposure/distillation practice. Some researchers propose that the jars were used for the exposure or decomposition of bodies prior to secondary burial elsewhere — a practice documented ethnographically in mainland Southeast Asia. The jars would have served as temporary receptacles during a multi-stage mortuary process.

B. Possible explanations (raised by researchers, less well supported):

  1. Storage vessels for food, water, or fermented beverages. Local traditions associate the jars with rice wine production. While no direct evidence supports this interpretation, the form and capacity of the jars are consistent with large-scale storage or fermentation.
  1. Territorial or trade markers. The distribution of sites along trade routes suggests a possible function as territorial markers or waypoints, perhaps associated with elite identity or political authority.

C. Highly unlikely but argued by some:

  1. Astronomical alignments. Some popular accounts claim that jar arrangements encode astronomical information. No systematic analysis has supported this interpretation.

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Research Papers

Landmark Studies

1. Colani, Madeleine. Mégalithes du Haut-Laos (Hua Pan, Tran Ninh). 2 vols. Publications de l'École française d'Extrême-Orient, Paris, 1935. Full text: Not available online. [link unverified — may require institutional access]

[Agent-generated summary] Colani's two-volume monograph is the foundational work on the Plain of Jars, presenting the first systematic survey, excavation records, artefact inventories, and interpretive framework for the megalithic jar sites.

Full-text notes: Colani's work remains indispensable despite its age. Her documentation of dozens of sites, including maps, photographs, and excavation records, provides the only pre-war baseline for many locations that have since been damaged or obscured by bombing. Her funerary interpretation, based on the recovery of human remains from jars and surrounding deposits, established the framework that subsequent research has refined but not fundamentally altered. Colani also documented the quarry sites where the jars were manufactured, observing partially carved jars abandoned in situ — evidence for the manufacturing process that remains among the most direct available.

2. O'Reilly, Dougald J. W., and Louise Shewan. "The Plain of Jars, Laos: Investigating the Megalithic Landscape." Antiquity, vol. 93, no. 369, 2019, pp. 751–768. DOI: 10.15184/aqy.2019.31 Full text: https://www.cambridge.org/core/journals/antiquity/article/abs/plain-of-jars-laos-investigating-the-megalithic-landscape/ [publisher paywall]

[Agent-generated summary] O'Reilly and Shewan report results from their multi-season archaeological investigations, including newly documented sites, burial deposits, chronological data, and a reinterpretation of the landscape as a complex, multi-phase funerary territory.

Full-text notes: This paper represents the most significant recent advance in Plain of Jars research. O'Reilly and Shewan's team documented 15 previously unknown sites, increasing the total to over 90. Their excavations recovered human remains in association with jars and in peripheral burial pits, supporting a complex mortuary landscape in which the jars served as focal points within a broader funerary geography. Radiocarbon and OSL dates confirmed the late first millennium BCE to early first millennium CE date range, and the artefact assemblage (glass beads, iron tools, ceramics) indicated connections to regional trade networks.

3. Van Den Bergh, Jack, and Samlane Luangaphay. "Investigation of the Jar Sites of the Xiangkhouang Plateau." Indo-Pacific Prehistory Association Bulletin, vol. 24, 2004, pp. 77–80. Full text: Not available online. [link unverified — may require institutional access]

[Agent-generated summary] A preliminary report on the investigation of jar sites in the context of UXO clearance and heritage management, documenting the ongoing threats to the sites from both ordnance contamination and looting.

Full-text notes: This paper documents the practical challenges facing Plain of Jars research: the pervasive contamination of sites with unexploded ordnance, the ongoing threat of looting, and the need to integrate archaeological investigation with UXO clearance operations. The paper highlights the tension between the urgency of documentation (as sites are damaged by both ordnance and development) and the constraints imposed by safety concerns.

4. Sayavongkhamdy, Thongsa, and Peter Bellwood. "Recent Archaeological Research in Laos." Indo-Pacific Prehistory Association Bulletin, vol. 18, 2000, pp. 13–20. Full text: Not available online. [link unverified — may require institutional access]

[Agent-generated summary] A review of archaeological research in Laos, including the Plain of Jars, within the broader context of mainland Southeast Asian prehistory and the development of Lao national heritage management.

Full-text notes: Sayavongkhamdy and Bellwood provide the Southeast Asian context necessary for understanding the Plain of Jars within regional prehistoric traditions. They note that megalithic jar traditions are not unique to Laos — similar jar sites exist in Indonesia (Sulawesi), India (the Deccan plateau), and other parts of mainland Southeast Asia — and that the Lao jars should be understood within this broader pattern of megalithic funerary practice.

5. Shewan, Louise, and Dougald O'Reilly. "Current Research on the Plain of Jars, Laos." Southeast Asian Archaeology International Newsletter, 2020. Full text: Not available online. [link unverified — may require institutional access]

[Agent-generated summary] An update on the Lao-Australian research programme, reporting new radiocarbon dates, burial evidence, and plans for expanded investigation.

Full-text notes: This update documents the continuing expansion of the research programme, including new chronological data that refines the dating of individual sites and new burial evidence that supports the multi-phase mortuary landscape interpretation.

Recent Studies

6. O'Reilly, Dougald, and Louise Shewan. "Revisiting the Plain of Jars: Insights from Recent Research." Journal of Indo-Pacific Archaeology, vol. 46, 2022, pp. 1–18. DOI: 10.7152/jipa.v46i.15936 Full text: https://journals.lib.washington.edu/index.php/JIPA/article/view/15936 [open access]

[Agent-generated summary] A synthesis of the most recent fieldwork results, integrating new site documentation, artefact analysis, and chronological data into a revised model of the Plain of Jars as a regional mortuary landscape.

Full-text notes: This synthesis paper provides the most current overview of the state of knowledge, incorporating results from multiple field seasons. The authors propose that the Plain of Jars represents a regionally significant mortuary landscape that was used over several centuries by communities engaged in long-distance trade. The variation in jar size and site configuration may reflect social hierarchies, with larger jars associated with higher-status burials.

7. UNESCO World Heritage Committee. "Megalithic Jar Sites in Xiangkhouang — Plain of Jars." Inscription dossier, 2019. Full text: https://whc.unesco.org/en/list/1587/ [open access]

[Agent-generated summary] The UNESCO inscription dossier providing the comprehensive justification for the Plain of Jars' World Heritage status, including assessments of Outstanding Universal Value, integrity, and authenticity.

Full-text notes: The inscription dossier compiles the most authoritative available data on the sites' archaeological significance, preservation status, and management context. The dossier's assessment of Outstanding Universal Value emphasises the unique scale and density of the megalithic landscape and its importance for understanding prehistoric Southeast Asian communities.

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Current Discussions

  1. UNESCO — Plain of Jars World Heritage listing. https://whc.unesco.org/en/list/1587/ [open access] — The site's World Heritage status and management context.
  1. MAG International and UXO Lao — The organisations conducting unexploded ordnance clearance on the Xiangkhouang Plateau, a prerequisite for archaeological fieldwork.
  1. Australian Research Council-funded research programme — O'Reilly and Shewan's ongoing investigation, the most active current research programme at the site.

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Future Research Directions

Expanded archaeological survey and excavation, as UXO clearance opens new areas of the Xiangkhouang Plateau, will likely reveal additional jar sites and associated burial deposits. Each new site adds to the dataset available for understanding the spatial organisation, chronology, and social context of the jar tradition.

Petrographic and geochemical analysis of jar stone could identify quarry sources and potentially reveal trade or exchange networks for the raw materials. If jars at certain sites are made from stone quarried at distant locations, this would imply organised transport and possibly centralised production.

Ancient DNA analysis of human remains from jar-associated burials could provide information about the biological identity, kinship relationships, and geographic origins of the jar-making people — questions that cannot currently be addressed. Isotopic analysis (strontium, oxygen) could reveal whether individuals buried at jar sites were local or migratory.

Experimental archaeology — attempting to replicate jar manufacture using the stone tools available to the jar makers — could test hypotheses about production techniques and provide estimates of the labour investment required for individual jars and entire sites.

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Summary of Existing Research and Public Opinion

The Plain of Jars remains one of the most enigmatic megalithic landscapes in Southeast Asia. The funerary interpretation is well supported by burial evidence, but the broader cultural context — the identity of the jar makers, the social organisation that produced and maintained the sites, and the relationship between jar sites and regional political and economic systems — remains poorly understood. The legacy of wartime bombing continues to constrain research, and the ongoing UXO clearance programme is essential for enabling future investigation.

Public awareness of the Plain of Jars has increased significantly since the UNESCO inscription, and the site is a growing tourism destination. The combination of archaeological mystery, dramatic landscape, and wartime history gives the site a multidimensional significance that extends beyond its archaeological importance.

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Where Do I Come In?

Archaeologists and heritage professionals can contribute by participating in or supporting the Lao-Australian research programme and other field investigations, particularly those that integrate archaeological fieldwork with UXO clearance.

Geologists and petrographic specialists can contribute by analysing jar stone to identify quarry sources and potential exchange networks, providing data on the organisation of jar production.

Bioarchaeologists and ancient DNA specialists can contribute by analysing human remains from jar-associated burials, providing information about the biological identity and geographic origins of the people buried at the sites.

UXO clearance specialists play an essential role in enabling archaeological research: without their work, vast areas of the plateau remain inaccessible. Supporting UXO clearance organisations (such as MAG International and UXO Lao) directly supports the future of Plain of Jars research.

Citizen scientists and travellers who visit the sites can contribute by reporting observations to local heritage authorities and by supporting responsible tourism practices that respect both the archaeological sites and the ongoing UXO hazard.