Dating Resin Coating on Pottery: The Spirit Cave Early Ceramic Dates Revised. (Method)
Lampert, C. D., Glover, I. C., Hedges, R. E. M., Heron, C. P., Higham, T. F. G., Stern, B., Shoocongdej, R., Thompson, G. B., Antiquity
During the summer of 1966, Chester Gorman, then a Ph.D student at the University of Hawai'i carried out archaeological excavations at the rock-shelter of Spirit Cave in the karst uplands of Mae Hong Son Province, Northwest Thailand (Figure 1), and he revisited the site in 1971 to extend the excavations. Throughout all levels of the cultural deposits, lithic, faunal and botanical materials were found. The majority of the cultural remains recovered from the site were typically Hoabinhian, characterised by "Sumatra-type cores, ochre-covered grinding stones, unifacially worked quartzite pebbles and utilised flakes" (Gorman 1969:672), but objects recovered from the upper levels included some new find types. Amongst these were a small number of pottery fragments, perhaps representing no more than 20 vessels. Some of the sherds were burnished, with plain surfaces, and a few were decorated with incised lines but the majority had cord-marking or net impressions on their exterior surfaces. Some sherds were further described as having "been coated with an organic resinous material" (Gorman 1972:96) after they had been fired. One of these sherds can be seen in Figure 2, bearing patches of resin on both interior and exterior surfaces. Potsherds were only present in Layer 1 and compacted into the surface of Layer 2. This abrupt variation in material culture marks the boundary between the Hoabinhian deposits of Cultural Level I and a period of cultural contact, which Gorman termed Cultural Level II.
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A series of radiocarbon dates, primarily obtained from bamboo-charcoal samples, taken from within distinct stratigraphic layers, indicated that the site dated to between 12 000 BP and 7500 BP, around a 5000 year time-span of continuous occupation and intermittent use (Gorman 1972).
Table 1 shows some of the published radiocarbon dates obtained for the upper layers of the site (Gorman 1972, Ehrich 1992). Based on these, the potsherds were originally considered to date to around 7500 BP. This small ceramic assemblage was therefore cited as amongst the earliest examples of pottery in the world (Solheim 1972). Solheim (1972) further speculated that the presence of pottery and the possibility that some of the plant remains may have come from deliberately cultivated plants might suggest a shift away from a purely hunter-gatherer economy, linking this with the early development of horticultural practices in Southeast Asia, although Yen (1977) considered the evidence for cultivation to be tentative.
However, reservations have since been expressed on the early date for the Spirit Cave ceramics. Higham (1989: 60) noted that there may have been a long hiatus between occupation of Spirit Cave during Cultural Level I and the emergence of the pottery fragments marking Cultural Level II. A single radiocarbon date, of 7622 [+ or -] 300 BP (FSU 317), is associated with the bottom of the thin deposit forming Layer 1, the uppermost excavation layer. The three somewhat earlier dates, FSU 314, GaK 1846 and BM 501, are associated with the surface of Layer 2 and may also be considered relevant to the defence for an early date for the pottery. However, it is largely on the date obtained from the sample taken from within Layer 1 that the possible debate hinges.
That there was later use of the rockshelter is evident from the presence of a number of log coffin burials within the Spirit Cave complex. It is plausible that the ceramics, being confined to the upper part of the site, might have originated from disturbance of these burials and their associated grave goods. If this were the case, the pottery could be of a later date than first thought. Supporting this theory is the stylistic similarity noted between some of the Spirit Cave ceramic fragments, particularly the cord-marked sherds, and pottery recovered from other rock-shelter sites with log coffin burials in Mae Hong Son Province (Shoocongdej, pers. …