A review of the curved lithic cleavers from the rainforest of southeastern South America

Abstract

South American lithic cleavers are heavy curved artifacts distributed throughout the tropical Upper Paraná Atlantic Forest in the southeastern lowlands of the subcontinent. The most reliable stratigraphic data and associated radiocarbon dates show that they were produced from the early-middle Holocene to the late-middle Holocene boundary. The cleavers were shaped by bifacial flaking and secondarily by pressure using pebbles, and to a lesser extent, thick flakes. The most used rock for its manufacture was silicified sandstone. The classic design of these tools features a thick, bi-concave neck with expanded shoulder, and a long, triangular and tapered blade with a rounded tip, which has undergone a rejuvenation process throughout its life cycle. Although they have some morphometric variations along their distribution range, they have the same bauplan. Indeed, the geometric morphometry analysis does not show significant differences between the designs of the cleavers from the Upper Paraná River in Argentina, and the Upper Uruguay in Brazil, reflecting the existence of a shared learning lineage in both valleys. Cleavers are recognized at sites that appear to have been residential camps, but quite often they are recovered isolated and distributed in the landscape, suggesting their use in obtaining resources. A fraction of them present a gloss on their tips visible to the naked eye. The microwear analysis of cleavers shows intense modifications in the first two to four cm from the tips of their blades, showing polished areas, and systematically orientated striations which are compatible with the processing of soft and semi-hard plant tissues, especially tubers. These results place these artifacts in the discussion about the systematic exploitation and even manipulation of plants in the Atlantic Forest during the early and middle Holocene.