Changing prehistoric Yapese pottery technology: a case study of adaptive transformation

Abstract

This study describes the processes of cultural adaptation to environmental conditions through an examination of ceramic technology. The case study involved eight months fieldwork in the Yap Islands, Western Caroline Islands, Micronesia, to obtain archaeological, ethnographic and environmental information.

Analyses of the mineral and chemical composition and physical characteristics of Yapese clays showed that two types exist on the island: very plastic metamorphic clay and nonplastic sedimentary clay. Analysis of sand samples from beach and river locations showed varying amount of calcareous sand grains.

Three types of pottery were distinguished in the archaeological deposits on the basis of temper and physical characteristics of vessel walls. Calcareous Sand Tempered (CST) and Plain potteries were made between 2000 and 600 years B.P. whereas Laminated pottery was made after 600 years B.P. Technological change between the three pottery types was shown by reconstructing the technology used and the physical properties of the products, using information about the mineral composition of the clays, tempering, forming, surface finish, vessel form, thickness, firing, strength and porosity.

Metamorphic plastic clay was used for making all three types of pottery. The major contrasting characteristic of the different potteries is differences in tempering behaviour. A steady improvement in firing technique over 2000 years was identified as the major cause for the changes observed.

CST pottery was tempered with fine calcareous beach sand. The clay tempered in this way was very workable but had a disadvantage of being easily damaged if fired at higher temperatures.

Plain pottery was tempered with a range of materials, such as burnt coral lime and coarse sand but not with calcareous sand. This variation with alternative tempers is interpreted as attempts to avoid the deleterious effects of heating calcareous sand. The quality of Plain pottery was not very high (weak, thick and straighter vessel wall), and the experiments did not result in an effective solution to the problems of CST pottery because technological replacement did not occur.

Laminated pottery was shown to be identical to the historically manufactured pottery, and was made with a unique technology. No temper was added to the highly plastic clay, and the techniques of forming, drying and firing were adapted to the low workability of the clay. The combination of these techniques produced a strong and durable layered vessel wall.

The thesis includes a published bulletin describing the excavations and a computer disk with a full catalogue of all pot sherds and scientific data.