Origin, distribution and domestication of the carob tree (Ceratonia siliqua L.)

The carob tree, which is a member of the Fabaceae family, is an agrosilvopastoral tree whose pre-Mediterranean tropical origin appears well established on the basis of genetic, fossil and physiological data. C. siliqua has recently been successfully introduced from the Mediterranean basin to other parts of the world that have a Mediterranean climate. In terms of its domestication, there is paleobotanical, philological, ecological and historical evidence to suggest that the species was spread by people from Arabia, where it took refuge during the Ice Age, to Mesopotamia and then on to the western Mediterranean. This "eastern refugium hypothesis" (ERH) postulates the existence of a single refuge for the carob tree in the eastern Mediterranean and a dissemination by humans to the west of the region concomitant with its domestication. However, recent results of phylogenetic and fossil analyses have revealed the existence of a western refuge, thus refuting the single ERH hypothesis and supporting local use and domestication of the carob tree from native populations throughout the Mediterranean. This paper advances other arguments of a historical, philological, ecological and sociocultural nature that support the existence of a western refugium and also emphasise the important role played by the Romans and particularly by the Arabs and Andalusians in the propagation and domestication of the carob tree in the western Mediterranean.