A matter of health

In 1950, Peter Williams-Hunt published a paper in Antiquity entitled ‘Irregular earthworks in eastern Siam: a review’. A former RAF pilot, he had pored over wartime aerial photos taken of the extensive Khorat Plateau in North-east Thailand. He was intrigued by the numerous enigmatic prehistoric sites, at first sight reminiscent of moats around a medieval castle, which are in fact occupation mounds surrounded by up to five concentric banks. Twenty years after his article was published, I found myself excavating within one of these sites, large enough to contain several modern villages, which lay alongside a salt pan. When we arrived to start excavations, it was the scene of intensive dry-season salt production. I have since excavated another four of these moated sites, and we confirmed Williams-Hunt’s conclusion that: ‘Further comment would be futile. The excavator’s spade alone will provide the final answer.’

Over the years, we have achieved several breakthroughs, all of which have only been made possible by collaborating with a large team of specialist colleagues. The most compelling question, was the purpose of the moats, some up to 40m wide. Long posited, this issue was resolved in a matter of days when we decided that the only way forward was to excavate right across them, beginning at the site of Noen U-Loke. We took the bull by the horns and hired a powerful digger that, within a day, had opened a trench several metres deep and nearly 200m in length. Bill Boyd, our geomorphologist, then mapped the stratigraphy before water rose up and filled the trench, finding that the moats were flat-based, with no hint of a defensive purpose. The banks had been built up by accumulating the surface soil in order to retain water fed from a nearby stream. This procedure was replicated at four other sites with the same results, and radiocarbon dating placed their construction in the later Iron Age, between 100 BC and AD 400.

Non Ban Jak from the air. These Iron Age moated sites were first described in 1950. The testimony of the spade is now unravelling their secrets.

Other insights followed: they were built over when the monsoon rains faltered, heralding centuries of relative aridity. Then blacksmiths began forging iron ploughshares and sickles, and the inhabitants, men and women, were interred in their own houses, some with remarkable wealth expressed in gold and silver, carnelian and agate, and quantities of bronze ornaments. Significantly, rice was now grown in permanent wet fields rather than dryland plots fed only by rainfall, and we concluded that the moats fed irrigation water into the new fields, ensuring a bountiful and predictable harvest. We found a house that had been burnt to the ground, leaving carbonised rice grains all over the kitchen floor, and now the dead were interred in graves filled with rice.

Taken together, all these pointers have underwritten a new model for social change that would rapidly lead to the foundation of early states, characterised by the rise of social elites, the wholesale development of irrigation agriculture, application of ploughing in demarcated fields, and the organisation of labour. One can add to the mix the introduction of exotic ideas and artefacts via emerging maritime exchange routes. However, all was not well. There was a dark side that is now being identified through the specialist studies of the prehistoric actors themselves.

Non Ban Jak is the last of the moated sites I have been lucky enough to excavate. During our five seasons there, we opened 200 human graves. At other sites, the skeletons have survived in a poor condition. Often there are concretions that accumulate on the bone surfaces and it is difficult if not impossible to remove this without causing damage. At Noen U-Loke, the rice that covered the bones seriously degraded them. But at Non Ban Jak they were not only found in near perfect condition, but in many cases it has been possible to extract DNA. One aspect became strikingly apparent, even as we excavated: there was a preponderance of infant graves. The fragility of these very immature bones was offset by the fact that such tiny dead were buried in protective lidded pots, so we knew we had another infant grave long before the bones came to light. In all, they accounted for 64.1% of all burials, the highest proportion so far recorded in prehistoric South-east Asia. Seven of the 125 infants died when 20-30 weeks from conception, 13 when aged 30-40 weeks, and 21 had just been born. A staggering 45 then survived for between one month and a year. Could this be linked to their mothers being in poor health?

This middle-aged man is one of several possible lepers who lived at Non Ban Jak during the late Iron Age. 

Let us pause here and consider their environment. The moats that encircled the town were filled with water fed from a local stream, but during the dry season the water was almost certainly stagnant. Beyond lay the rice fields, again for half the year under water, which would have surely attracted malarial mosquitoes. A few adult crania bore the signs of resistance to malaria but the onset of anaemia. We sieved all material removed from the square to secure a complete collection of shellfish and fish bones. There is a greater number of shell species than has been encountered in any earlier site in this region, and their potential impact on human health is sobering, particularly if they were not properly cooked. Wading barefoot through foetid water into a rice field to harvest or collect shellfish in itself is not to be recommended. When I spent a day behind a water-buffalo-drawn plough years ago, I was constantly having to dodge what the buffalo was depositing.

The two dominant species that colonise wet rice fields are a good source of protein. However, they are also the intermediate hosts of a liver fluke that causes echinostomiasis, with symptoms including tiredness and weight loss. Gnathostomiasis can be contracted through consuming inadequately cooked fish, eels, frogs, and birds; exactly the range of species expected to reside in the moats around these Iron Age sites. Having entered the liver or eye, this parasite will often cause blindness, coma, and death. Indoplanorbis is a small shellfish commonly found in ponds and rice fields. It has serious health implications as the intermediate host for parasitic worms that cause bilharzia, with symptoms including diarrhoea, liver and kidney failure, and bladder cancer. The list goes on and on. Turning to the adult bones themselves, two middle-aged men and a woman presented, on their skull and limb bone, lesions compatible with leprosy. Other individuals have the same bone deformation that is caused by tuberculosis. Despite the difficulty of tracing a town plan when the sites are so deep, with layer upon layer of house foundations to unravel, our strong impression is that the houses huddled together, separated by narrow lanes. This density of people would surely have encouraged the spread of transmissible diseases.

Written in enamel

It is notable how many contributors are now listed as authors on most innovative scientific papers. When we published our first results on ancient DNA from South-east Asia, I was one of 67 authors. Another recent paper on Yamnaya DNA and the origins of the Indo-Europeans has more than 200. A few weeks ago, I received a surprise email from my colleague Marc Oxenham to say that an article on the adult teeth from Non Ban Jak was on the brink of publication in the Journal of Archaeological Science: Reports. The attached copy included me as a co-author – I had, after all, co-directed the excavation and thus provided the basic data. While devouring its contents, I found myself Googling to understand words I have never encountered, foremost being ‘perikymata’, which are successive growth lines in a tooth, each forming over a period of about a week. Disruptions in their formation, known as linear enamel hypoplasia (LEH), is another sure sign of poor health.

The results of this pioneer study make grim reading. All but one of the 48 adults surveyed suffered from health issues that caused LEH. The really remarkable point about the growth lines is that you can pin down the age of each individual when this occurred, the duration of the illness, and the recovery period; a unique window on the health status of the community. When you have a sample covering four mortuary phases over a period of five centuries, incorporating men and women, you can home in on changes over time and between the sexes. I read that there was an average of 2.5 episodes of ill health per adult, the onset varying between 1.4 and 4.2 years of age. The combined period of stress and recovery lasted between 27 and 269 days. It is a depressing thought that these 47 people represent the small fraction of the population that survived to adulthood. When compared with other similar analyses, we find that the situation was as bad as that among the Krapina Neanderthals.

At face value, you would imagine that the Iron Age town of Non Ban Jak thrived. Its inhabitants countered climate change by the innovative use of reservoirs and canals, and by harnessing the strength of water buffaloes to haul ploughs, just as their descendants do to this day. They engaged in long-distance exchange to acquire their glass, agate, and carnelian ornaments. Their blacksmiths forged spears and sickles, bronze specialists cast their bangles and belts, and potters produced splendid vessels fired in enclosed kilns. However, it is also the responsibility of archaeologists to trace an accurate and complete assessment of daily life, and this can be best achieved by exhuming and intensively analysing the remains of the inhabitants. That life was a struggle at Non Ban Jak is undeniable. It is a salutary lesson that innovations to confront climate change can have unexpected consequences.

Charles Higham is a Professor at Otago University in New Zealand, and an authority on Cambodia's Angkor civilisation and Ban Non Wat in Thailand.