BY BEN THOMAS
Everywhere we look, the world seems to be full of binary distinctions. “Morning people” versus “night owls.” Introverts and extroverts. Cat people and dog people. And of course, the classic cannabis dichotomy: sativa and indica.
Most of us know the difference from firsthand experience: Sativa strains make for heady, energetic daytime highs, and indica strains serve up a soothing dose of late-night couch-lock—while hybrids provide a blend of both.
But is this distinction really as sharp as it appears? Not when we look to history, or to the latest scientific research. In fact, the “sativa/indica” binary reveals some surprising truths about how “species” get defined in the first place—and how slippery those definitions can become when we put them under a microscope.
It all boils down to a classic case of “lumpers versus splitters.” You find these people in every fandom, hobby, and scientific discipline: those who lump similar things into broad categories—and their archenemies, the people who prefer to split categories (and hairs) as finely as possible. Do the Fantastic Beasts movies count as Harry Potter films? Depends whether you ask a lumper or a splitter.
In 1753, the eminent Swiss naturalist Carl Linnaeus lumped all cannabis plants into a single species: Cannabis sativa. Case closed, it would seem—until 32 years later, when the equally eminent French biologist Jean-Baptiste Lamarck split cannabis into two species: C. sativa, which had lighter, narrower leaves, and C. indica, whose leaves were darker and broader.
The issue appeared settled until 1930, when the Russian botanist Dmitrij Janischewsky claimed to have identified a third species (or subspecies, depending who you ask): Cannabis ruderalis, whose flowering cycle differed from those of its two cannabis cousins. In a 1974 paper, a team of American biologists agreed with Janischewsky’s three-way split, arguing that the three “species” exhibited not only physical differences, but also distinct THC-to-CBD ratios.
Although the “ruderalis” thing never really caught on, the “sativa/indica” distinction proved invaluable for 21st-century dispensaries, who could recommend “sativa” strains for an energizing head high, “indica” strains for a relaxing body buzz, and “hybrid” strains for the best of both worlds. The problem was, however, that salespeople tended to lump (or split) cannabis strains based on their effects, rather than on any real biological differences.
Today, we can breed cannabis to produce any THC/CBD ratio we want, in just about any concentration we want. We’ve got strains that focus almost entirely on THC—while gardeners in anti-weed states can grow legal “hemp” strains that produce massive CBD concentrations while generating so little THC that they’re not legally considered “marijuana” at all.
It’s also becoming increasingly common for cannabis vendors to distinguish strains based on their terpene profiles. Terpenes, a class of biomolecules produced by a wide variety of plants, have been demonstrated to lend cannabis cultivars their distinctive scent profiles—and since these compounds provide a variety of health benefits for plants, many budtenders are now claiming terpenes may be “even more important than THC” in delivering weed’s anti-anxiety and couch-lock effects.
A 2018 study found that crossbreeding between sativa and indica strains has effectively made them all hybrids, rendering the distinction "almost meaningless."
However, scientific research on cannabis terpenes is still in the very preliminary stages—and more importantly, most terpene molecules are destroyed by smoking, vaping, or cooking with cannabis resin. As a result, the majority of cannabis chemistry experts agree that the so-called terpene “entourage effect” is little more than an interesting hypothesis, which we’re going to need a lot more data to confirm or disprove. In the meantime, all we know for sure is that different cannabis plants produce different terpene profiles, whose functions are unclear.
And even despite these differences, a 2020 study led by Jeff Chen at the UCLA Cannabis Research Initiative concluded that all strains of cannabis are too molecularly similar to be split into separate species. What’s more, a 2018 study led by Cambridge University’s John M. McPartland found that crossbreeding between sativa and indica strains has effectively made them all hybrids, rendering the distinction “almost meaningless.” Like chihuahuas and rottweilers, our favorite weed strains may differ wildly in size, shape, and temperament—but deep down in their DNA, they’re all mutts.
Which begs the question:
The most obvious answer is, “animals (or plants, or fungi) that look alike.” But here we run into immediate difficulties, because nature is chock-full of plants and animals and fungi that look very similar, yet differ in extremely important ways. For example, a tasty and harmless Amanita caesera mushroom looks deceptively like an Amanita muscaria, which can send you on a psychedelic trip—or possibly kill you, depending how much of it you eat.
Today, most biologists define a species as “a group of organisms which can or do reproduce with each other but not with other groups.” Even this definition turns out to be slippery: Donkeys and horses can make baby mules together, so does that make them the same species, or two different ones? Why are domestic dogs considered different species from wild wolves, which can (and do) interbreed with them? Does the word “interbreed” even mean anything, if two separate species cannot, by definition, breed with one another? In other words, shouldn’t “interbreeding" be, by definition, kind of a logical impossibility?
Questions like these have vexed philosophers since the days of ancient Greece. When Plato defined a human as a “featherless biped,” his nemesis Diogenes came back with a plucked chicken and announced, “Here, Plato; I’ve brought you a man.” Two thousand years later, Charles Darwin fared no better. “It is really laughable to see what different ideas are prominent in various naturalists' minds, when they speak of 'species,’” the great biologist wrote to a friend. “It all comes, I believe, from trying to define the undefinable."
Nature itself—in the immortal words of Alan Watts—"is wiggly."
In other words, a species is not a physical, measurable object in the natural world. Rather, it’s an attempt by humans to squeeze nature into neat little boxes, when nature itself—in the immortal words of Alan Watts—“is wiggly.” Lions and tigers can make ligers. Bacteria can swap DNA with entirely different species. And cannabis plants can exhibit a staggering range of variation while remaining indistinguishable from each other, right down to the molecules.
So while dispensaries may recommend “sativa” and “indica” strains as if the distinction was a clear-cut scientific fact, the truth is that it’s much more a matter of opinion. Much like how (contrary to the widespread myth) tequila doesn’t make us any “crazier” than any other type of alcohol, a “sativa” strain like Blue Dream can provide a refreshingly chill high—while an “indica” like Girl Scout Cookies can prove surprisingly energizing in a different setting.
In short, every cannabis plant (like every dog) is unique—and so is your body’s endocannabinoid system. The only way to find out for sure what a new variety will do for you is to sample it for yourself, and remember that finding the "right" strain that suits your particular needs at any given time is an ever-shifting personal journey.
Ben Thomas is a journalist and novelist who's lived in 40+ countries. He specializes in telling stories from the frontiers of science, history, culture, and the cosmos—and the points where all these fields intersect. Find him on Twitter at @writingben.