Modelling ancient areas for date palms (Phoenix species: Arecaceae): Bayesian analysis of biological and cultural evidence

Abstract

Our aim in this study is to build a model for the expansion of date palms (Phoenix spp., Arecaceae) that can be linked to domestication processes. Palaeontological and archaeobotanical evidence concerning date palm is extremely diversified around the Mediterranean Basin and in West Asia, mainly consisting of date fruit remains, but also including leaf fragments and other plant remains. This biological evidence is further compared with cultural evidence (coins, pottery, ancient texts) and the present distribution of Phoenix spp. in the area. Bayesian methods working with likelihood and conditional probabilities are successfully applied to generate a model for displaying in maps the ancient distribution of palm groves in terms of probabilities. The model suggests that the domestication of Phoenix dactylifera occurred mainly east of 30°E, probably in the Jordan Valley area, starting before 7 kya and, in a westward shift, that this was gradually superposed onto pre-existing local western populations of the same genus, especially in the Nile valley. It appears that this mainly affected the P. dactylifera western cluster (P. excelsior, P. atlantica, P. iberica). However, other taxa persisted as independent species (P. theophrasti, P. canariensis).