Cannabis in Asia: its center of origin and early cultivation, based on a synthesis of subfossil pollen and archaeobotanical studies

Abstract

Biogeographers assign the center of origin of Cannabis to "Central Asia," mostly based on wildtype plant distribution data. We sought greater precision by adding new data: 155 fossil pollen studies (FPSs) in Asia. Many FPSs assign pollen of Cannabis or Humulus (C-H) to collective names (e.g., Cannabis/Humulus or Cannabaceae). To dissect these aggregate data, we used ecological proxies. C-H pollen in a steppe assemblage (with Poaceae, Artemisia, Chenopodiaceae) was identified as wild-type Cannabis. C-H pollen in a forest assemblage (Alnus, Salix, Quercus, Betula, Robinia, Juglans) was identified as Humulus. C-H pollen curves that upsurged alongside crop pollen were identified as cultivated hemp. Subfossil seeds (achenes) at archaeological sites also served as evidence of cultivation. FPSs and archaeological sites were mapped using geographic information system (GIS) software. The oldest C-H pollen consistent with C. sativa dated to 19.6 million years ago (mya), in northwestern China. However, Cannabis and Humulus diverged 27.8 mya, based on molecular clock analysis. We bridged the temporal gap between the divergence date and the oldest pollen by mapping the earliest appearance of Artemisia. These data converge on the northeastern Tibetan Plateau, which we deduce as the C. sativa center of origin. This co-localizes with the first steppe community that evolved in Asia. From there, Cannabis first dispersed west (Europe by 6 mya) then east (eastern China by 1.2 mya). Cannabis pollen in South Asia appeared by 32.6 kya. The earliest Cannabis seeds were found in Japan, 10,000 BCE, followed by China.

A classification of endangered high-THC cannabis (Cannabis sativa subsp. indica) domesticates and their wild relatives

“…Cannabis populations have undergone both natural and human selection. Fossil pollen studies show that Central and South Asian populations occupied their separate ecological niches for at least 32,600 years (McPartland et al 2019). Their phenotypes may be presumed to have diverged, due to environmental adaptation and natural selection.…”

“…We hypothesize that this was the route taken by Cannabis into the Himalaya, hence into peninsular India. It arrived relatively recently, the oldest fossil pollen in all of South Asia dates back only 32,600 years (McPartland et al 2019). The morphology of var.…”

Untargeted Metabolomic Analyses Reveal Chemical Complexity of Dioecious

“…Notwithstanding the targeted measurement of 14 major and minor cannabinoids, we identified several putative unknown phytocannabinoid-like metabolites upregulated in female flowers but were unable to unequivocally assign annotations to these compounds. The annotation of metabolites was limited by the availability of reference compounds to compare observed MS 1 and MS 2 information for correct annotation, thus highlighting the need to establish a comprehensive reference library or database for Cannabis metabolites. Development of phytocannabinoid-specific accurate-mass MS n fragmentation spectral libraries coupled with nuclear magnetic resonance analysis will improve the confidence of compound structure annotation and mitigate challenges associated with the discrimination of multiple cannabinoid species and their constituent isomers and stereoisomers within complex botanical matrices.…”

“…Cannabis, a member of the family Cannabaceae, is a highly heterozygote multi-use anemophilous (wind pollinated) flowering plant genus, which is believed to have originated in Central Asia. [1] Taxonomic assignment and speciation of Cannabis is unresolved. [2] Despite this ambiguity, a monotypic status is widely supported on the basis that physiological and genetic barriers to gene flow are underreported.…”

“…Fossil evidence in the form of pollen deposits and seed remains suggest widespread use across Eurasia dating back several thousand years. [1,4] In addition to traditional uses for food and fibre, plants also have recreational and medicinal value due to their secondary metabolites, particularly phytocannabinoids and terpenes.…”