The Roots of Cannabis: Origin and Uses in Ancient Central Asia
Genomic sequencing reveals some Chinese landraces as close descendants from which hemp and marijuana landraces have derived.
Forget dual passports — cannabis has multiple citizenships in just about every country and terrain you can think of, from the wintry steppes of Siberia to the equatorial climes of South America. And as any fan of the cannabis travelogue series The Strain Hunters would know, there’s no shortage of wild (also known as “feral”) strains growing in remote areas throughout Asia. At which point in human history those feral strains became the cultivated hemp and cannabis varieties we know and love has been an ongoing question for plant researchers. This makes the publication of an ambitious paper, detailing the theoretical roots of cannabis domestication, a major event for fans of cannabis genetics.
The authors of the paper, which is titled Large Scale Whole Genome Sequencing Unravels the Domestication History of Cannabis Sativa, hold that, “Contrary to a widely accepted view, which associates Cannabis with a Central Asian center of crop domestication, our results are consistent with a single domestication origin of C. sativa in East Asia, in line with early archaeological evidence.” Further, they state “some of the current Chinese landraces and feral plants represent the closest descendants of the ancestral gene pool from which hemp and marijuana landraces and cultivars have since derived.” (For clarification, Webster defines a landrace as “… a local variety of a species of plant or animal that has distinctive characteristics arising from development and adaptation over time to conditions of a localized geographic region.”)
The paper’s findings were derived from the careful genomic sequencing of 110 varieties of hemp and medicinal/recreational cannabis found in Asia, Europe and North and South America. Researchers separated these varieties into four groups: “hemp type”, “drug type”, “drug type feral” and “basal” cannabis varieties, which are genetically related to the aforementioned Chinese landrace/feral strains. From there, they used genomic dating to estimate an approximate domestication date of 12,000 years ago, which falls within the early Neolithic period. Cross-referencing their data with archeological finds in East Asia and China, the researchers found that a small number of early domesticated cannabis plant types expanded into the plants now used for food, medicine and, yes, even recreational purposes. They believe that cannabis was cultivated as a multipurpose crop until around 4000 years ago, at which point growers started selecting certain varieties of the plant for specific hemp and drug uses and cannabis began its slow march towards Southeast Asia, Europe, and eventually Africa and the New World.
In addition, the researchers examined specific portions of the genome to show which genes correspond to physical characteristics of hemp and cannabis, and how the genes that eventually give birth to THC and CBD are expressed in both the industrial and recreational forms of cannabis. In general, the researchers found that industrial and psychoactive cannabis varieties could not be distinguished by their potential ability to make THC or CBD. Genes to make both were found in both the hemp-type and drug-type plants genomes they analyzed. “The results call into question, from both a biological and functional point of view, the current binary categorization of Cannabis plants as “hemp” or “marijuana,” the paper adds.
The data for the paper came from field studies performed by researchers and geneticists in several of the countries where the sampled domesticated plants and their feral descendants are grown, namely Pakistan, China and Switzerland. Once the paper was published, it was reported in the popular press.
In response to the paper, Dr. Michael Purugganan of NYU disputed the findings in the New York Times, estimating the beginnings of domestication at 7500 years. He suggested that the sample size of 110 plants was too small. Another’s critique suggested that the invisible hand of human intervention throughout the history of cannabis, even when coupled with genetic information can only say so much about how or if the plant changed “naturally.” Of course, the plant’s illegality throughout the world hasn’t helped to increase our understanding of these dynamics either.
Still, the paper has created a treasure trove of data for plant geneticists the world over. One of the paper’s Chinese authors specifically highlighted the potential improvements his country could make to his country’s hemp crops based on the research. And regardless of any particular nation’s current laws, these details will probably come in handy for those looking to perform some innovations on their own crops as well, whether it’s for medicine, fiber, or fun. Clearly, they wouldn’t be the first.