ABSTRACT
Cannabis sativa is an angiosperm-a member of the flowering plants that dominate terrestrial parts of Earth. Although there is some evidence of an older origin, most fossil evidence demonstrates that flowering plants appeared at least by the Lower Cretaceous geological period, about 125 million years ago, and were diversifying into modern plant families by the Middle Cretaceous, 100 million years ago. The Cannabaceae family traditionally has been defined as comprised of two genera, Cannabis and Humulus (Small 1978a). Grudzinskaya (1988) added the fossil genus Humulopsis to the Cannabaceae and split Humulus into two genera (although only Humulus is currently accepted). Humulus species are vines and easily distinguished from Cannabis. However, the fruits (achenes) are very similar and could be confused with each other. Older texts commonly use the obsolete orthography Cannabinaceae and Cannabiaceae for the family (Miller 1970). Recent molecular evidence indicates that the family is best considered as composed of about 10 genera (Sytsma et al. 2002; Yang et al. 2013; Figure 2.1). McPartland and Guy (2004a), on the basis of parasite relationships of Cannabis and related families, suggested that the Cannabaceae lineage evolved no earlier than 34 million years ago. Except for pollen grains, fossils tracing back millions of years when C. sativa first evolved are lacking, and its age of origin has not been determined with accuracy.
