Seasonal mortality patterns in primates: implications for the interpretation of dental microwear

Poggetti Vecchi (Tuscany, Italy): A late Middle Pleistocene case of human-elephant interaction

A paleosurface with a concentration of wooden-, bone-, and stone-tools interspersed among an accumulation of fossil bones, largely belonging to the straight-tusked elephant Palaeoloxodon antiquus, was found at the bottom of a pool, fed by hot springs, that was excavated at Poggetti Vecchi, near Grosseto (Tuscany, Italy). The site is radiometrically dated to the late Middle Pleistocene, around 171,000 years BP. Notable is the association of the artifacts with the elephant bones, and in particular the presence of digging sticks made from boxwood (Buxus sp.). Although stone tools show evidence of use mainly on animal tissues, indicating some form of interaction between hominins and animals, the precise use of the sticks is unclear. Here we discuss about the role played by the hominins at the site: paleobiological and taphonomic evidence indicates that the elephants died by a natural cause and were butchered soon after their death. The associated paleontological and archeological evidence from this site provides fresh insights into the behavior of early Neanderthals in Central Italy. The discovery of Poggetti Vecchi shows how opportunistically flexible Neanderthals were in response to environmental contingencies.

The temporal scale of diet and dietary proxies

Diets estimated from different proxies such as stable isotopes, stomach contents, and dental microwear often disagree, leading to nominally well-supported but greatly differing estimates of diet for both extinct and extant species that complicate our understanding of ecology. We show that these perceived incongruences can be caused by proxies recording diet over vastly different timescales. Field observations reveal a diet averaged over minutes or hours, whereas dental morphology may reflect the diet of a lineage over millions of years of evolution. Failing to explicitly consider the scale of proxies and the potentially large temporal variability in diet can cause erroneous predictions in any downstream analyses such as conservation planning or paleohabitat reconstructions. We propose a cross-scale framework for conceptualizing diet suitable for both modern ecologists and paleontologists and provide recommendations for any studies involving dietary data. Treating diet in this temporally explicit framework and matching the scale of our questions with the scale of our data will lead to a much richer and clearer understanding of ecological and evolutionary processes.

A tool for determining duration of mortality events in archaeological assemblages using extant ungulate microwear

The seasonality of human occupations in archaeological sites is highly significant for the study of hominin behavioural ecology, in particular the hunting strategies for their main prey-ungulates. We propose a new tool to quantify such seasonality from tooth microwear patterns in a dataset of ten large samples of extant ungulates resulting from well-known mass mortality events. The tool is based on the combination of two measures of variability of scratch density, namely standard deviation and coefficient of variation. The integration of these two measurements of variability permits the classification of each case into one of the following three categories: (1) short events, (2) long-continued event and (3) two separated short events. The tool is tested on a selection of eleven fossil samples from five Palaeolithic localities in Western Europe which show a consistent classification in the three categories. The tool proposed here opens new doors to investigate seasonal patterns of ungulate accumulations in archaeological sites using non-destructive sampling.