Julieta Gómez Otero

Shifting niches of marine predators due to human exploitation: the diet of the South American sea lion (Otaria flavescens) since the late Holocene as a case study

Abstract. Stable isotope ratios of carbon and nitrogen in archaeological and modern bone samples have been used to reconstruct the dietary changes of the South American sea lion Otaria flavescens from the late Holocene to the present in the southwestern Atlantic. We sampled bones from archaeological sites in northern-central and southern Patagonia, Argentina, and bones housed in modern scientific collections. Additionally, we analyzed the stable isotope ratios in ancient and modern shells of intertidal molluscs to explore changes in the isotope baseline and allow comparison between bone samples from different periods after correction for baseline shifts. Results confirmed the trophic plasticity of the South American sea lion, demonstrated the much larger impact of modern exploitation of marine resources as compared with that of hunter-gatherers, and underscored the dissimilarity between the past and modern niches of exploited species. These conclusions are supported by the rather stable diet of South American sea lions during several millennia of aboriginal exploitation, in both northern-central and southern Patagonia, and the dramatic increase in trophic level observed during the twentieth century. The recent increase in trophic level might be related to the smaller population size resulting from modern sealing and the resulting reduced intraspecific competition. These results demonstrate how much can be learned about the ecology of modern species thanks to retrospective studies beyond the current, anthropogenically modified setting where ecosystem structure is totally different from that in the pristine environments where current species evolved.

Cabezales líticos del holoceno tardío en Patagonia Meridional: diseños y asignación funcional

Since the early settlement circa 11.000 AP to the Historical Period, aboriginal hunter-gatherers from Southern Patagonia used different weapons with lithic heads which size and design changed through time. In this work we present and discuss the results of the functional attribution of 47 points of the area studied over the basis of a model proposed by Norma Ratto. The results indicate that different weapon systems were used in the late Holocene: thrusting spears, thrown spears, and bows and arrows. The

Archaeology of the Península Valdés: Spatial and Temporal Variability in the Human Use of the Landscape and Geological Resources

The archaeological record of Peninsula Valdes shows this area was intensively used by native hunter-gatherers since at least 5000 years BP to the nineteenth century. These populations located their settlements in sandfields across the littoral zone, primarily on coastal bajadas and low marine terraces near fixed shoals of molluscs. Archaeofaunal studies and stable isotope analyses (13C and 15N) of human bone samples indicate that they had a terrestrial-marine diet including guanaco meat, land plants, mollusks, fishes and pinnipeds. The old inhabitants of the peninsula profited local rocks and clay minerals to manufacture their artefacts. To lithic technology, they used small pebbles of silica and basalt, big pebbles of riolites and granites, consolidated sandstones and fossil cetacean bones. The basic toolkit comprised knives, end-scrapers, side-scrapers, drills, burins, notches, fishing weights and a variety of projectile points. The big pebbles were used as manos, hammer stones and anvils, while sandstones and fossil bones were primarily employed in milling activities. With respect to pottery technology, the abundance and good quality of local clay sources allowed its important development in the final late Holocene. Most vessels present oval or spherical shapes, straight sides and concave bases. All these features are suitable for domestic activities, e.g. preparing, storing and/or cooking food and liquids. These hunter-gatherers did not live isolated from other populations: the presence of foreign rocks and of three ceramic vessels, which might have been manufactured in northwest Patagonia or perhaps central Chile, indicates that they took part in an extensive trading net since at least the late Holocene.