Using an innovative method, archaeologists were able to date giant stone jugs in Laos for the first time. Researchers could not get close to them for a long time, since the territory had been mined since the civil war of 1960-1973. It was assumed that the jugs were associated with burials found nearby, but analysis showed that they are much older – they are over 3 thousand years old.
The Valley of the Pitchers is one of the two major antiquities and tourist attractions in Laos along with the temple ruins of Wat Pu. Until now, it remained unknown where the mysterious stone jugs came from in Xieng Khouang province in the central part of the country.
According to legend, the vessels were once the bowls of the giants who inhabited the area in ancient times. Another legend tells of King Khung Chung, who defeated enemies and ordered his subjects to start making vessels for lao lao rice wine.
The pitchers are scattered across 60 sites. Most of them are cylindrical in shape, but there are also oval and rectangular jugs. Each of them has a height of 0.5 m to 3 m and has a weight of about 6 tons. There are also discs: it is assumed that these are lids from pots. In the manufacture of these products, rocks, granite and sandstone were used.
The first archaeological research was carried out by the French in the 1930s
Until recently, strange jugs weighing up to six tons left many questions unanswered – neither the age of the blocks, nor their purpose, nor the place of their production are known. An international team of scientists finally managed to unravel one of the mysteries of the Valley of the Pitchers – the time of the appearance of these mysterious megaliths carved from stone.
For decades, scholars have assumed that the jugs were part of ancient burial rites
Due to the danger of excavations in this area, archaeologists for a long time did not manage to closely study the megaliths. The reason is in the millions of unexploded American shells and bombs left in this territory after the civil war in Laos, which took place half a century ago. Today, hundreds of people a year fall victim to these bombs in Laos.
For this reason, the territory of the Valley of Pitchers has been surveyed by scientists for less than 10 percent. In recent years, however, specialists have managed to identify several safe areas and conduct several expeditions to study the jugs, some of which stand alone, some are grouped into large clusters.
“Until recently, it was impossible to estimate when the pitchers first appeared in this place and where they came from,” the scientists write in an article published in the journal PLOS One.
During the research, they managed to answer one of the main questions – when were the jugs made. The scientists were able to estimate the age using the so-called optically stimulated luminescence (OSL) method, which is widespread today in geology and archeology.
It is based on an estimate of the time of the last exposure of a sample to natural radiation, in other words, using physical methods, it is possible to understand when a particular mineral last saw sunlight. The typical range of determined ages is from a few hundred to 100,000 years.
All minerals contain trace concentrations of radioactive elements – uranium, thorium, potassium. After a long time, they disintegrate, and the ionizing radiation emitted by them is absorbed by other minerals, in particular, quartz and feldspar, in the crystal lattices of which there are damages, electron traps.
If the sample is irradiated with a certain light, the crystal will luminesce the more, the more energy accumulated in the traps while the sample was in the dark.
This innovative technique helped establish that the jugs were installed in their places at the end of the second millennium BC. Dating helped to answer one more question – are the jugs somehow connected with previously discovered nearby human burials – whole skeletons and individual piles of bones.
Radiocarbon dating dates these burials to the 9-13th centuries AD. This means that the jugs appeared several thousand years before the burials, but what they served for is still unknown.
“The data presented strongly indicate the installation of megaliths, which preceded the funerary activity around the jugs, and the reuse of these sites, which had long ritual significance,” the authors say.
Another unsolved mystery is the origin of the jugs. Examination of some of the megaliths indicated that the jugs may have been hewn out of a stone deposit eight kilometers from the valley. However, how their creators moved the jugs weighing several tons is still a mystery.