Systematics at the Levels of Family, Genus, and Species.

New concepts are reviewed in systematics, including phylogenetics and nomenclature. The family now includes , , and eight genera formerly in the . Grouping , , and actually goes back 250 years. Print fossil of the extinct genus (=) reveals that lost a sibling perhaps 20 million years ago (mya). print fossils are rare (=3 worldwide), making it difficult to determine when and where she evolved. A molecular clock analysis with chloroplast DNA (cpDNA) suggests and diverged 27.8 mya. Microfossil (fossil pollen) data point to a center of origin in the northeastern Tibetan Plateau. Fossil pollen indicates that dispersed to Europe by 1.8-1.2 mya. Mapping pollen distribution over time suggests that European went through repeated genetic bottlenecks, when the population shrank during range contractions. Genetic drift in this population likely initiated allopatric differences between European (cannabidiol [CBD]>Δ-tetrahydrocannabinol [THC]) and Asian (THC>CBD). DNA barcode analysis supports the separation of these taxa at a subspecies level, and recognizing the formal nomenclature of subsp. and subsp. . Herbarium specimens reveal that field botanists during the 18th-20th centuries applied these names to their collections rather capriciously. This may have skewed taxonomic determinations by Vavilov and Schultes, ultimately giving rise to today's vernacular taxonomy of "Sativa" and "Indica," which totally misaligns with formal and . Ubiquitous interbreeding and hybridization of "Sativa" and "Indica" has rendered their distinctions almost meaningless.