Bacterial bioerosion in human and animal bones from subtropical environments (Northern Pampa/Middle Paraná River Basin, República Argentina)

Abstract

Microbial bioerosion is a major diagenetic factor determining the long-term survival of archaeological bones as well as the quantity and quality of the biological information retrievable from them. In spite of this, information about bioerosion is still scarce from a worldwide perspective, with most of the data coming from the European continent. In this connection, the primary aim of this paper is to present the first results of an ongoing study oriented at identifying patterns of bacterial bioerosion in human and animal bone samples recovered at different Late Holocene archaeological sites from the subtropical environments of the Middle Paraná River Basin and the Northern Pampa Plain, República Argentina. These results differ in some respects from those obtained in other regions and climates, particularly the temperate belt of Europe, but are consistent with data from a nearer zone, the southern Pampas of East-Central Argentina. The main differences with most of the European samples investigated so far lie in the higher intensity of the bacterial attack on bones, which is reflected in the placement of the first and second frequency distribution modes at lower values of the Oxford Histological Index (0 and 3, respectively), an absence of cases with excellent histological preservation (i.e. OHI = 5) and, finally, a higher frequency and intensity of bioerosion in disarticulated animal bones and in those of humans interred as secondary burials. The causes of the observed differences are still not well understood, being probable that they are linked to higher levels of bacterial activity in the soils of this subtropical region of southern South America.