Taphonomy and paleoecological implications of fossorial microvertebrates at the Middle Paleolithic open-air site of Nesher Ramla, Israel

Abstract

Variation in taphonomic modes, which describe the characteristics of fossil depositional environments, is an important but much understudied aspect of the formation of microvertebrate assemblages. This study examined an assemblage of microvertebrate remains which was recovered from archaeological deposits in a deep karst depression at an open-air setting – a unique and so far undocumented type of depositional environment in the southern Levant. Taxonomic and taphonomic characteristics of the assemblage reveal a striking difference from other known assemblages in the region from cave and fluvial depositional settings. This includes especially low density, taxonomic diversity and skeletal element survivorship. Three of the four taxa are fossorial or semi-fossorial and their remains dominate the assemblage indicating strongly an accumulation history which involves underground burrow deaths of fossorial animals. This is supported by additional evidence from skeletal modifications showing rare evidence of weathering, extensive in situ fragmentation where the fragments remain fused together and abundant evidence for light abrasion. These taphonomic patterns suggest extended underground protection of the remains, followed by limited dispersal within a sedimentary matrix likely due to movement from the surrounding soil mantle into the karst depression through colluviation processes. This taphonomic reconstruction has significant implications for understanding the long record of hominid occupation at the Middle Paleolithic site of Nesher Ramla. Phases of high density of the remains along the section correspond with glacial phases of Marine Isotope Stages (MIS) 6 and 5a-4 indicating an association between enhanced fossorial activity and environmental conditions during glacial stages. Intense deposition of cultural remains was recorded only during MIS 6, however, and this leads us to suggest that continued low intensity hominid presence in the upper layers of the site is related either to change in the usefulness of the site for hominid subsistence activities as it was being filled with sediments or to demographic changes linked to the arrival of new populations during MIS 5a-4. Detailed paleoenvironmental sequences which are recovered directly from hominid sites are critical for testing such hypotheses.