Name: Where Did the Cannabis Plant Come From?
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While the origins of the cannabis plant remain unknown, geneticists can trace its evolution and identify its closest living relative.

What cannabis DNA can reveal about the plant’s evolution.

While the origins of the cannabis plant remain unknown, geneticists can trace its evolution and identify its closest living relative.

Where Did the Cannabis Plant Come From?

What cannabis DNA can reveal about the plant’s evolution.

Evolution

Where Did the Cannabis Plant Come From?Published: December 16, 2021Narrator: Where did the cannabis we know today come from? Its wild beginnings remain unknown. But by looking at the plant’s genes, we can identify its closest living relative.Daniela Vergara: Hops, which we use for beer, is the closest existing species to cannabis. Narrator: Plant geneticists estimate that some 28 million years ago, cannabis and hops plants diverged. Today, cannabis contains special compounds—called cannabinoids—molecules like THC, which can make someone high, and CBD. Daniela Vergara: And we know that the cannabinoids appeared in cannabis, but hops does not have them. Narrator: Which means that the cannabinoids appeared after cannabis split from hops. We’re not sure if or how the evolution of these compounds benefitted cannabis, but they may have protected the plant against UV light or kept it from being eaten. Whatever the reason, humans took note and started growing cannabis for different uses.Daniela Vergara: We do know that there’s many different cultures, ancient cultures that have been using it for a long time. The Chinese, for example, the Greeks and the Romans, the Indians have used it for medicinal purposes, but also for industrial purposes, rope and canvases so they would use it for paper and also for medicinal purposes and for rituals Narrator: By studying the genes of over 100 different varieties of cannabis, geneticists estimate that around 12,000 years ago, the wild cannabis plant broke into two lineages. One of which was likely bred for crops. And this crop lineage split again about 4,000 years ago, into two more groups: hemp plants selected for fiber, food, and textiles, and a second one used for their psychoactive properties.These two characteristics—strong fibers and psychoactive effects—are largely due to domestication and the process of artificial selection. Which is when certain traits are chosen by people and reinforced through breeding. This kind of selective breeding, which started thousands of years ago, continues today.Dina Saleh: So let’s say they wanted to have high THC level in the plant, so they were breeding for high THC or they wanted certain colors. So that’s how they were selecting for the plants that we currently have in the market that have this available. Narrator: Both the hemp and psychoactive varieties belong to a single species — Cannabis sativa.Daniela Vergara: And so far we think it’s one species that has a lot of variation, both physically. So phenotypically and genomically so in the DNA.Narrator: Today, federal law draws a distinction between the two. The difference lies in their THC levels. Daniela Vergara: The legal definition of hemp is anything that produces less than 0.3 percent THC. And we found that those groupings from the industry really do not mean much. And we think that it’s more related to how people feel when they consume the different products.Narrator: Hemp and the psychoactive varieties may have some distinct physical features that set them apart. Hemp is taller, fibrous, and is less bushy than the psychoactive plant.In recent years, cannabis growers have artificially selected and bred plants with even higher amounts of THC. As a result, today’s cannabis may be far more potent than its ancestor - or even the cannabis of a couple decades ago. And now, scientists have managed to produce both THC and CBD without the plant at all - by genetically engineering bacteria and yeast.Dina Saleh: I am wondering how will governments and legal institutions look at this innovative aspect that we do have in science and that is actually growing big in the industry.Narrator: Completely replacing the cannabis plant, though, is unlikely. Humans have been cultivating it for thousands of years. And a relationship like that is hard to break.

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NOVA investigates the story of cannabis from the criminalization that has disproportionately harmed communities of color to the latest medical understanding of the plant. What risks does cannabis pose to the developing brain? How much do we know about its potential medical benefits? As cannabis becomes socially accepted, scientists are exploring its long-term health consequences. (Premiered September 29, 2021)Check out a previously recorded panel discussion and audience Q&amp;A featuring experts and producers from "The Cannabis Question" <a href="https://youtu.be/nSTT5RZ_hxA">here</a>.

As state-legalized cannabis spreads, NOVA explores its little-known risks and benefits.

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Where Did the Cannabis Plant Come From?

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Support Provided By

Explore More

Why is Researching Cannabis so Hard?

Georgia’s First Black-Owned Hemp Farm

How Does a Brain on THC Compare to a Brain on CBD?