The deep evolutionary roots of Cannabis and Humulus: fossils, genomics, and geography

Although the duo Cannabis and Humulus includes some of the earliest and most versatile domesticated plants, their evolution remains poorly understood. We revise the fossil record of Cannabis and Humulus to constrain the age and geographic location of the plants. Exquisite fossils from the Eocene of North America assigned to Humulus lupulus, suggest that the common hop may represent a true ‘living fossil’ that has experienced a prolonged period of evolutionary stasis. Our molecular clock analyses reveal that the common ancestor of Cannabis and Humulus diverged in the Eocene to Paleocene, coinciding with the emergence of steppe biomes in Eurasia during the late Eocene, constraining the geographical origin of both plants and offering a framework for testing causal hypotheses of their divergence.