Approaching the study of camelid bone size change in the meridional portion of the South Central Andes is a significant subject especially when the assemblages are associated to radiocarbon dates placed at a time of social transition from an extractive to a producer economy. In this sense, this paper presents the results of applying osteometric techniques on a set of 10 elements from the Peñas Chicas 1.5 site dated around 3800 BP. The analysis shows the presence of at least three individuals, one of which corresponds to an Andean guanaco (Lama guanicoe) morphotype. The second and the third are similar in size to a modern llama (Lama glama) in their ‘intermediate’ and ‘cargo’ morphotypes. This is consistent with patterns already seen for sites from the Argentinian and Chilean Puna where the identification of larger individuals than the Andean guanaco modern standard shows the early stages of an increasingly bone size variability of South American camelids. This paper contributes with new data to understand the complex processes that occurred in the South Central Andes that led to the domestication of one of the most conspicuous animals in the archaeological record of the Argentinian Northwest. Copyright © 2012 John Wiley & Sons, Ltd.