Indica vs Sativa: What the DNA Actually Says

Watch the episode · 4:26

Indica or sativa? It is the first question everyone asks. One is tall, thin-leafed and slow; the other short, broad-leafed and fast. But a 2021 genetic study found that, across the genome, you cannot tell the labels apart. And the names themselves ended up the wrong way round.

Source · Watts et al., Nature Plants (2021)

Where the names began ▶ 0:34

These names are older than you think. In 1753 Linnaeus named the hemp grown in Europe Cannabis sativa, meaning "cultivated". In the 1780s Lamarck named a second kind, Cannabis indica, from plants collected in India. By the 1980s both had become growers' slang.

Here is the twist. According to a 2020 botanical review, the tall, narrow-leafed plants growers now call sativa have their roots in South Asia, including India: the original home of the name indica. The short, broad-leafed "indicas" trace back to Afghanistan and Central Asia, the afghanica plants of episode 12. Same words, swapped plants.

Source · McPartland & Small, PhytoKeys (2020)

What the DNA says ▶ 1:25

In 2021, researchers compared the labels with the plants' DNA. They analysed the chemistry of nearly 300 samples and the genomes of 137. Genome-wide, indica-labelled and sativa-labelled plants were genetically indistinct.

Source · Watts et al., Nature Plants (2021)

Then a 2022 study of almost 90,000 lab-tested samples from six US states found the same story in the chemistry: a sample labelled indica would likely have a terpene profile indistinguishable from one labelled sativa or hybrid.

Why? Decades of crossbreeding. Most modern plants are hybrids of hybrids. It is like a deck of cards shuffled for fifty years: the label on the box no longer tells you what is inside.

What the labels track ▶ 2:19

So are the labels meaningless? Not quite: they follow your nose. The 2021 study found the labels did line up with a handful of aroma compounds. Indica labels went with myrcene, guaiol and eudesmol; sativa labels with bergamotene and farnesene. All are controlled by clusters of terpene genes, like the ones in episode 8 on aroma.

In other words, growers and breeders have mostly been naming plants by smell, not by ancestry. And when the 2022 study sorted samples by chemistry instead, three clear aroma families appeared: caryophyllene and limonene, myrcene and pinene, and terpinolene and myrcene. Even labelling by the dominant terpene sorted samples better than indica or sativa.

Source · Smith et al., PLOS ONE (2022)

The real family tree ▶ 3:11

The DNA does have a family tree, just not the one on the label. A 2016 study of more than 300 varieties found at least three major genetic groups: hemp, broad-leaf drug types and narrow-leaf drug types.

Source · Lynch et al., Crit. Rev. Plant Sci. (2016)

The original, unmixed versions of those groups survive mainly in traditional landraces, which botanists now describe as critically endangered.

Source · McPartland & Small, PhytoKeys (2020)

For growers ▶ 3:37

Look at the plant and its terpene profile, not the sticker. A plant's shape tells you how it will grow: tall and stretchy, or short and bushy. Its terpene profile tells you how it will smell. The indica or sativa label tells you much less than you would think.

The names began in the 1700s and then swapped plants. Genome-wide the labels are indistinct; they mostly track a few aroma genes. The real groups are hemp, broad-leaf and narrow-leaf types.