Date palms (Phoenix dactylifera, Arecaceae) are of great economic and ecological value to the oasis agriculture of arid and semi-arid areas. Zehdi-Azouzi et al. investigate genetic diversity levels and population genetic structure by genotyping a collection of 295 accessions ranging from Mauritania to Pakistan using a set of SSR markers and a plastid minisatellite. A Bayesian clustering approach shows that the genotypes can be structured into two different gene pools: an Eastern pool, consisting of accessions from Asia and Djibouti, and a Western pool, consisting of accessions from Africa. The results confirm the existence of two ancient gene pools that have contributed to the current diversity of date palm.