Today, Cannabis sativa is widely used around the world for various purposes. Its history of human use dates back thousands of years. However, the versions of cannabis you encounter today are far different than what was available when domestication efforts of the plant were first carried out. Between then and now, the hand of humankind has worked to domesticate cannabis for a medley of purposes, resulting in the cultivars we have today.
How We Got Here
Today, there are countless varieties of cannabis in the marketplace, in private homes, and in the wild. However, at one point, the plant only grew wild and did not have the genetic variety that exists today.
To understand this evolution of cannabis through domestication, a group of scientists set up a study that would analyze the whole-genome profile 110 genome accessions from around the world in an “unprecedented global sampling effort.”  Their goals were to find out how cannabis varieties domesticated to where they are today. As a caveat, the researchers state that it is nearly impossible to reconstruct an exact breeding history of many of the samples because breeding was principally done secretively to avoid criminal prosecution.
The samples collected including both hemp and drug-type accessions from a mix of feral, landrace, and cultivar plants. Sequencing of the samples was carried out, and the results pointed the team to East Asia as the sole location where domestication efforts of cannabis began during the early Neolithic period, circa 10,000 BCE. Additionally, the team found that modern Chinese feral and landraces were the closest relatives to those ancient plants first domesticated so many years ago, concluding that “[A]ll current hemp and drug cultivars diverged from an ancestral gene pool currently represented by feral plants and landraces in China.”
Another interesting finding was that selecting cannabis plants for fiber or for drug content had significant effects on future generations. Over time, selecting for a higher delta-9-tetrahydrocannabinol (THC) content resulted in the loss of the production of cannabidiolic acid (CBDA), the precursor for cannabidiol (CBD) and to tetrahydrocannabinolic acid (THCA, the precursor of THC, when selecting for higher fiber content.
This finding demonstrates, says the team, that Cannabis sativa is neither hemp or drug-type cannabis naturally. Rather, it’s likely that it naturally contains a mix of both cannabinoids that varies from plant to plant. Current high-THC and high-fiber plants are the result of breeding and artificial selection.
The researchers’ work is another valuable resource for understanding the plant. The genomic, demographic, and phylogenetic research they carried out on the 110 accessions has given the cannabis world a wealth of information regarding the origin of domestication, effects of domestication efforts, and current-day expressions of the genetic diversity of these plants. Agriculture and medicine are two fields that the researchers feel will find their work helpful as a comprehensive base of information.
Image Source: NickyPe
Reference: Ren G, Zhang X, Li Y, et al. Large-scale whole-genome resequencing unravels the domestication history of Cannabis sativa. Sci Adv. 2021;7(29):eabg2286. [journal impact factor = 14.14; times cited = 15]