Evolution and Classification of Cannabis sativa (Marijuana, Hemp) in Relation to Human Utilization

Abstract

Cannabis sativa has been employed for thousands of years, primarily as a source of a stem fiber (both the plant and the fiber termed "hemp") and a resinous intoxicant (the plant and its drug preparations commonly termed "marijuana"). Studies of relationships among various groups of domesticated forms of the species and wildgrowing plants have led to conflicting evolutionary interpretations and different classifications, including splitting C. sativa into several alleged species. This review examines the evolving ways Cannabis has been used from ancient times to the present, and how human selection has altered the morphology, chemistry, distribution and ecology of domesticated forms by comparison with related wild plants. Special attention is given to classification, since this has been extremely contentious, and is a key to understanding, exploiting and controlling the plant. Differences that have been used to recognize cultivated groups within Cannabis are the results of disruptive selection for characteristics selected by humans. Wild-growing plants, insofar as has been determined, are either escapes from domesticated forms or the results of thousands of years of widespread genetic exchange with domesticated plants, making it impossible to determine if unaltered primeval or ancestral populations still exist. The conflicting approaches to classifying and naming plants with such interacting domesticated and wild forms are examined. It is recommended that Cannabis sativa be recognized as a single species, within which there is a narcotic subspecies with both domesticated and ruderal varieties, and similarly a non-narcotic subspecies with both domesticated and ruderal varieties. An alternative approach consistent with the international code of nomenclature for cultivated plants is proposed, recognizing six groups: two composed of essentially non-narcotic fiber and oilseed cultivars as well as an additional group composed of their hybrids; and two composed of narcotic strains as well as an additional group composed of their hybrids.

Can we make cannabis safer?

“…The most abundant of the cannabinoids are delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) which the plant produces in different ratios from the precursor cannabigerol (CBG), based on genes that code for certain enzymes (THCA-synthase and CBDA-synthase) 12 . Hence, increased THC content in cannabis will be at the cost of CBD content.…”

Genomic and Chemical Diversity inCannabis

“…kafiristanica) are sometimes cited (Schultes et al, 1974). Even though an extensive monograph on the genus has recently been published (Small, 2015a), limited genetic and experimental data leave the questions of taxonomy unresolved (Clarke and Merlin, 2015;Small, 2015b).…”

Industrial Hemp in North America: Production, Politics and Potential

“…Cotton accounts for about 85% of the natural fiber textile market worldwide, while hemp accounts for less than 0.5% [12]. Although hemp pulp is not as profitable as wood pulp, and hemp has more environmental concerns regarding water consumption, soil erosion, and soil nutrient depletion [13], a niche market in Europe has developed for hemp cigarette paper. High quality bast is used along with other natural fibers for a variety of fiber biocomposites for automobiles [14,15].…”

“…It has the potential of efficiently employing stocks of livestock manure, although synthetic fertilizers, which are less desirable from a sustainability perspective, are usually employed in developed nations. One of the primary environmental claims for hemp is the potential to save trees, but da Siva et al [13] concluded that hemp fiber presents higher environmental impacts than eucalyptus paper in all of the environmental categories they analyzed. However, hemp produces environmentally-friendly manufactured products, including thermal insulation, carbon-sequestering bioplastics, and lightweight concrete substitutes that reduce transportation costs [23].…”