For thousands of years, humans have lit up around the world, enjoying the high that comes from cannabis.
But the controversial politics surrounding the drug has made it difficult for scientists to figure out its genetic origins. Where did cannabis come from and how did it evolve into the potent green that brings us pleasure?
Scientists finally have an answer to that question — and the evolution of modern-day cannabis and how it diverged from its very close relative hemp is even wilder than you might think.
New research published Friday in the journal Science Advances used genetics to trace the ancient birthplace of Cannabis sativa, from which we harvest pot today.
The cultivation of marijuana has much longer roots than we previously understood, according to the study — including evidence that our cultivation of pot may have led to the extinction of pure, wild, ancient strains of cannabis.
Cannabis “is one of the first cultivated crop species,” Luca Fumagalli, a co-author on the study from the University of Lausanne’s Laboratory for Conservation Biology, tells Inverse.
“Few crops have been under the spotlight of controversy as much as Cannabis sativa.”
How they did it — The researchers studied 110 genomes of Cannabis sativa using molecular analysis and “next-generation DNA sequencing” according to Fumagalli.
From their DNA analysis, the researchers build phylogenetic trees that show the relationships between and evolution of four genetically distinct groups of cannabis.
- Basal cannabis — This group is “sister to all other cannabis” categories, including all human-grown or “cultivated” hemp and psychoactive cannabis in the world. It includes wild plants and traditional cannabis hybrids, known as “landraces,” found in modern China.
- Hemp — This group includes all hemp varieties found around the world. Hemp is a variety of Cannabis sativa that is distinguished from other cannabis strains by its lower levels of tetrahydrocannabinol (THC) — the psychoactive ingredient that makes cannabis such a potent drug. Hemp, unlike its psychoactive counterpart, is not typically considered a drug and was traditionally used to make fiber for clothing and other materials.
- The first group of “drug” cannabis — This group includes wild strains of cannabis with drug-like properties similar to marijuana from China, India, and Pakistan, as well as one cultivated cannabis variety from India.
- The second group of “drug” cannabis — This group includes varieties of cannabis with drug-like properties that have been cultivated around the world.
This crucial basal cannabis group hadn’t been detected in previous research — a fact that Fumagalli found “very surprising.”
What they found — Through these genetic groupings, specifically, the basal cannabis grouping, scientists learned:
- The origin of cultivated or domesticated cannabis can be traced to East Asia, including parts of modern-day China. The finding challenges previous research stating that cultivated cannabis originated in Central Asia.
- The split between ancient basal cannabis and modern cultivated cannabis occurred roughly 12,000 years ago, placing cannabis in the distinguished categories of one of the first cultivated crops on Earth
- These early cultivated cannabis crops formed separate hemp and drug cannabis genetic groups about 4,000 years ago
This date coincides with the first appearance of fiber artifacts in East Asia, which spread west to Europe, according to archaeological evidence from the Bronze Age. Fiber from hemp is a popular source of clothing, food, and oil after a comeback in recent years.
The researchers state that psychoactive cannabis spread from East Asia to India around 3000 years ago. In the last thousand years, the drug reached Latin America and Africa, though it didn’t get to North America until much more recently — around the beginning of the twentieth century. European colonists introduced hemp varieties to North America in the 1600s, which were replaced by Chinese varieties by the 1850s.
Ultimately, the researchers find strong genetic differences between hemp and drug cannabis in their study. However, they also conclude cannabis was likely used as a “multipurpose” crop — not just a drug — in East Asia for thousands of years before humans used selective breeding to turn it into the potent, THC-laden green we know today.
“Possibly, ancient cannabis was a multipurpose crop — fiber, food, medicine, recreational — until 4,000 years ago, when it started to undergo strong artificial selection for either fiber production (hemp) or increased cannabinoid synthesis (marijuana),” Fumagalli says.
In fact, the human cultivation of cannabis had such a strong effect on the genetic evolution of cannabis that researchers suggested the pure wild ancestors of cannabis sativa have gone extinct.
Therefore, the human hand may have effectively engineered the most controversial plant into existence.
Why it matters — Due to the controversial and illicit nature of cannabis, which remains illegal in many countries and states in the U.S., it’s been difficult to track its genetic origins and evolutionary history.
The scientists write: “Clandestine drug breeding” has contributed to “the difficulties for reconstructing the species’ domestication history.”
This study takes a remarkable first step in tracing the evolutionary origins of modern cannabis, especially at a time when many lawmakers are reconsidering whether or not to legalize the drug.
As the researchers note: “Few crops have been under the spotlight of controversy as much as Cannabis sativa.” Their findings shed light on the complex history of cannabis evolution and domestication, helping us understand how it became the controversial crop it is today.
What’s next — Although Fumagalli doesn’t have any specific plans to expand on the research at the moment, the findings themselves provide enough fodder for heated debate among weed enthusiasts, geneticists, and drug regulators.
Through their research, the scientists were able to trace the genetic differences between hemp and psychoactive cannabis, with differences in gene sequences that code for the cannabinoid CBD in hemp and THC in other strains, respectively. Hemp is characterized by its lower THC content than its counterparts, which is why it doesn’t produce the typical “high” sense of other cannabis strains.
Although the scientists found genetic divergence in the expression of THC and CBD genes in all cannabis strains studied, they also found five hemp samples that contain more genetic complexity than we previously thought.
The evolutionary findings challenge the traditional legal divide between hemp and pot, suggesting it might be more arbitrary than scientific in reason.
The researchers state: “As such, 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.’”
So, in order to resolve the present-day cannabis debate, perhaps we need to look to an unexpected place: its evolutionary past.
Abstract: Cannabis sativa has long been an important source of fiber extracted from hemp and both medicinal and recreational drugs based on cannabinoid compounds. Here, we investigated its poorly known domestication history using whole-genome resequencing of 110 accessions from worldwide origins. We show that C. sativa was first domesticated in early Neolithic times in East Asia and that all current hemp and drug cultivars diverged from an ancestral gene pool currently represented by feral plants and landraces in China. We identified candidate genes associated with traits differentiating hemp and drug cultivars, including branching pattern and cellulose/lignin biosynthesis. We also found evidence for loss of function of genes involved in the synthesis of the two major biochemically competing cannabinoids during selection for increased fiber production or psychoactive properties. Our results provide a unique global view of the domestication of C. sativa and offer valuable genomic resources for ongoing functional and molecular breeding research.