Aim  This study intends to improve our understanding of historical biogeography of olive domestication in the Mediterranean Basin, particularly in the north‐western area. Location  Investigations were performed simultaneously on olive stones from extant wild populations, extant cultivated varieties from various Mediterranean countries, and archaeological assemblages of Spanish, French and Italian settlements. Methods  A combination of morphometrics (traditional and geometrical) allowed us to study both the size and shape of endocarp structure. Concerning shape, a size‐standardized method coupled with fitted polynomial regression analysis was performed. Results  We found morphological criteria for discriminating between wild and cultivated olive cultivars, and established patterns of morphological variation of olive material according to the geographical origin (for extant material) and to the age of the olive forms (for archaeological material). Levels of morphological convergences and divergences between wild olive populations and cultivated varieties are presented as evidence. Main conclusions  Morphological changes of endocarps of olive under domestication at both geographical and chronological scales provide new criteria for the identification of olive cultivars. They allow to determine the origins of cultivated forms created and/or introduced in the north‐western Mediterranean regions and to understand how human migrations affected the rest of the Western Mediterranean regions. A model of diffusion of olive cultivation is proposed. It shows evidence of an indigenous origin of the domestication process, which is currently recognized in the north‐western area since the Bronze Age.

Although several proxies for the inference of precipitation have been proposed, evidence of changes in aridity during the Holocene is scarce, and most is only qualitative. Moreover, precipitation regimes show relatively poor spatial correlations and can exhibit contrasting responses to global climate trends in different areas. Thus, there is a need to concentrate efforts at the local scale in order to increase the spatial resolution of palaeoclimate records, especially regarding water availability in semiarid zones. We propose the analysis of carbon isotope composition (d 13 C) in fossil charcoal (routinely recovered from archaeological sites) to quantify changes in water availability in the past. We applied this approach to reconstruct variations in aridity during the last four millennia in the Ebro Depression (NE Iberian Peninsula). First, we studied the effect of carbonization over a range of temperatures (300-500 1C) on the d 13 C of Aleppo pine (Pinus halepensis Mill.) wood cores, collected from nine locations in NE Iberian Peninsula with distinct water availability. Despite significant changes in d 13 C caused by carbonization, the original climatic signal of wood d 13 C was well preserved. Moreover, d 13 C shifts induced by this process were successfully corrected by accounting for variation in charcoal carbon concentration (%C). After removing the effect of carbonization, we estimated annual precipitation (P) and the ratio between annual precipitation and evapotranspiration (P/E) from the d 13 C of fossil charcoal. In general, estimated water availability in the past was higher than present values, indicating that latter-day (semiarid) conditions are mostly due to recent climate changes. The good agreement between our findings and other evidence indicates that the analysis of d 13 C in charcoal may be useful to expand current palaeoclimate records as it provides a complementary (and quantitative) source of information to assess climate dynamics.

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Està subjecte a una llicència de Reconeixement-NoComercial-SenseObraDerivada 4.

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