An extensive genomic study has determined that cannabis (hemp and marijuana) was first domesticated 12,000 years ago in East Asia and not in the center of the continent.
Domesticated for millennia, cannabis (Cannabis sativa) is used alternately as a source of textile and oil fibers (hemp), as well as for its medicinal and recreational properties (marijuana). Hemp and marijuana differ, among other things, by their relative content of Cannabidiol (CBD) and Tetrahydrocannabinol (THC), the two most abundant molecules among a hundred other so-called “cannabinoids”, only secreted by this species and involved in the chemical defense of the plant.
While hemp generally produces more CBD than THC, marijuana, on the other hand, contains very high amounts of cannabinoids and especially psychoactive THC. “The mode of action of these two molecules is simple: CBD and THC bind to receptors in the central nervous system and cause a wide range of effects, including alleviating the symptoms of neurological disorders. In recent years, in addition, the therapeutic potential of cannabis has experienced a strong resurgence of interest, “says Luca Fumagalli, lead scientist on the study, published in Science Advances in a statement.
How did the domestication processes of this universal plant come to such structural and chemical differences? Few studies have analyzed the subject, especially due to the legal restrictions in force in most countries, which makes sample collection complicated, if not impossible. Until now, researchers have also focused more on the biomedical effects of cannabis, than on its genetics and evolutionary history.
Using unprecedented global sampling, scientists led by Fumagalli sequenced and analyzed the complete genomes of more than a hundred specimens of diverse provenance and nature. These included, among others, wild plants (ancient cultivated plants that returned to nature) collected in the field in Asia, sometimes rare and forgotten local varieties, as well as historical and modern cultivars of hemp and marijuana from agronomic companies, shops and the Vavilov Institute in Saint Petersburg, the largest cannabis seed bank in the world. This effort was supplemented by publicly published genome data, particularly from North American marijuana growers.
OF THE FIRST, WITH WHEAT AND BARLEY
“Contrary to a general opinion, according to which cannabis was domesticated for the first time in Central Asia, our results tend rather to have a unique origin in East Asia, dating back to the early Neolithic, that is, about 12 ‘ago .000 years, reveals Luca Fumagalli. Therefore, cannabis would be one of the first species to be cultivated, along with wheat and barley. “
Unexpectedly, the researchers also found that some traditional and wild Chinese varieties form a previously unknown genetic line, which differs widely from the one that gave rise to the hemp and marijuana varieties found all over the planet today.
The evolution of the cannabis genome also suggests that our ancestors would have cultivated the plant for versatile use over a very long period of time. Today’s highly specialized varieties are said to come from selective crops started only about 4,000 years ago, optimized for the production of fibers on the one hand (hemp) or cannabinoids on the other (marijuana).
“Our work made it possible to dispel the doubt about the survival of Cannabis sativa in the wild: it would probably not remain, because all the wild plants analyzed are genetically close to cultivars, and therefore they do not constitute populations of natural origin”, emphasizes Fumagalli.