Origins of the Weipa Shell Mounds

Abstract

The shell mounds at Weipa on the west coast of Cape York Peninsula are thought by archaeologists to be among the world's largest prehistoric middens. The mounds appear to be composed almost entirely of whole and fragmented shell valves of the cockle Anadara granosa and artefacts have been recovered from them. Stone (1989), however, proposed that the tall, steep-sided shell mounds were not built by shellfishing Aborigines but by generations of mound-building Scrubfowl Megapodius r einwar dt. This thesis aims to determine the tenability of the Scrubfowl hypothesis by first testing the hypothesis of human origin. It then aims to establish a geographical and chronological context in which to interpret the origins of the shell mounds. From the literature it is evident that physical and biological processes of mound formation are far more certain and universal than cultural processes. Cheniers and barriers are common features of the world's coastlines and may form mounds through quirks of sediment supply or erosion. Mound-building organisms include megapodes, termites and ants, alligators and crocodiles, and fossorial rodents. Human occupation mounds are distinguishable by architectural features and related cultural remains. Mounds of doubtful human origin include the shell mounds of the Americas, Europe and southeast Asia. These mounds have morphostratigraphic features which strongly suggest that they are natural shoreline deposits, not massive shell middens. In the Andaman Islands, New Caledonia and southeastern Australia there are also mounds considered cultural in origin which may have been built by megapodes. The hypothesis that the Weipa shell mounds are the result of repeated Aboriginal shellfishing and occupation has been tested by dating a sequence of ten shells from the Kwamter mound. The results show that most of the shells in the sequence are roughly the same radiocarbon age. This casts serious doubt on the hypothesis of human origin. An examination of the interior surfaces of a selection of shell valves was also undertaken to determine if the shells contain any evidence for shellfish death offshore. Although microborings likely to have been produced by endolithic cyanobacteria were recorded, it is possible that these are post-depositional in origin as seven genera of cyanobacteria have been cultured from the shells. Mapping and auguring of coastal deposits at two locations along the Mission River has revealed the natural origins of some of the Weipa shell mounds. Essentially, the growth of the mounds reflects the development of the local chenier plains. Shell mounds have formed where the sea has concentrated coarse Anadara granosa shell whereas mounds composed of sand and gravel are present where these sediments predominate. At Prumanung whole Anadara valves have been transported by wave-action to the crest of the modem beach forming a coarse shell berm. At Uningan the prominent shell mounds originated as small, isolated shell cheniers. The hypothesis that Scrubfowl have transformed these natural shell deposits into tall, steep-sided mounds is tenable. Habitats favourable to Scrubfowl are associated with each location. Stanner's (1961) belief in the natural origins of the Weipa shell mounds is supported by this thesis. Only the mound-building Scrubfowl is needed to explain their unusual shapes and vertical exaggeration. The strong likelihood that these mounds are natural shell deposits raises serious questions about basic principles of shell midden archaeology. It is concluded that new methods for distinguishing between natural and cultural shell deposits are needed.