Titolo della tesi: The palaeonvironmental context of the Early and Middle Pleistocene at Melka Kunture archaeological site (Upper Awash Valley, Ethiopia), as evidenced by stable isotope analysis
Stable isotope analyses are a well-established and powerful tool to determine valid information on palaeodiet, palaeoenvironment, and palaeoecology (Bibi et al. 2013; Bocherens et al. 1996; Cerling et al. 2015; Lee-Thorp et al. 2010; Levin et al. 2008; Rivals et al. 2018). The method has been widely applied on Pleistocene archaeological sites in eastern Africa at medium and low altitudes (Ascari et al. 2018; Bedaso et al. 2010; Negash et al. 2020; Rivals et al. 2017; Semaw et al. 2020; Uno et al. 2018), but the literature is lacking isotopic reconstructions of ecological condition at high elevation.
Here, are reported carbon and oxygen stable isotope composition (13C, 18O) of fossil teeth enamel (carbonates) from Melka Kunture (MK) prehistoric site, located in the Ethiopian highland (~2000 m a.s.l.), in order to provide palaeoenvironmental insights. The measurements of 13C/12C and 18O/16O isotopic ratios were performed on 178 fossil teeth representing a various range of taxa (Hippopotamidae, Bovidae, Equidae, Suidae, Giraffidae, and Crocodylidae) to test the extension of the vegetation types. Collectively, 310 enamel samples (bulk and intra-tooth) have been analyzed. The carbon isotopic results of hippopotamids, bovids, equids, suids, and giraffids indicate a range of foraging strategies across the pure C4 diets to mixed C3-C4 diets, with variations between ~1.95 Ma and ~0.6 Ma (Mega annum) (Early and Middle Pleistocene). In contrast, the bulk and intra-tooth carbon isotopic ratios of crocodiles suggest that these Pleistocene reptiles ate herbivores that consumed C3 plants. The intra-tooth results of hippo, equid, and suid teeth indicate C4 diets and stable water conditions during the lifetime of the sampled mammals. The isotopic data, which emphasize the presence of open space conditions as C4 high-elevation grasslands, are consistent with pollen and phytolith analysis, indicating extended mountain grasslands, with a different abundance of mesophytic grasses, mountain forests, woodlands, and bushlands. However, it should be kept in mind that isotopic results from teeth enamel reflect the feeding strategies and the ecological behaviour of the analyzed taxa, fossil pollen allows to describe the plant types present even at a certain distance from the site, while phytolith data allow characterizing the distribution of the “on the spot” plants at the time of deposit formation. These complementary data encourage a combined approach among distinct methods that can yield more detailed palaeoenvironmental and ecological insights.