Cannabis has been domesticated in East Asia, new study finds


Written by Mike Ives; Joy Dong and Maria Cramer contributed reporting.

People who feel the effects of marijuana are subject to what scientists call “divergent thinking,” the process of finding solutions to a loosely defined question. Here’s one to ponder: where does the grass come from? No, not where it was purchased, but where and when was the plant first domesticated.

Many botanists believe that the Cannabis sativa plant was first domesticated in Central Asia. But a study published Friday in the journal Scientists progress suggests that East Asia is the most likely source and that all existing strains of the plant come from an “ancestral gene pool” represented by wild and cultivated varieties growing in China today.

The study’s authors found the plant to be a “predominantly multipurpose crop” cultivated around 12,000 years ago during the early Neolithic period, possibly for fiber and drug purposes.

Farmers began cultivating the plant specifically for its mind-altering properties around 4,000 years ago, as cannabis began to spread across Europe and the Middle East, the study’s authors said.

Michael Purugganan, a biology professor at New York University who read the study, said the usual assumption about early humans was that they domesticated plants for food. “This seemed to be the most pressing problem for humans at the time: how to get food,” said Purugganan, who was not involved in the research. “The suggestion that even at the beginning they were also very concerned about fiber and even intoxicants is interesting. This would raise questions about the priorities of these Neolithic societies.

A 2016 study by other scientists said the earliest records of cannabis came mainly from China and Japan, but most botanists believe it was probably first domesticated in the eastern part of the country. Central Asia, where wild varieties of the plant are widespread.

Gene study

Genetic sequencing from the latest study suggests the species has a “unique domestication origin” in East Asia, the researchers wrote. By sequencing genetic samples of the plant, they found that the species had most likely been domesticated during the early Neolithic period. They said their conclusion was supported by pottery and other archaeological evidence from the same period found in present-day China, Japan and Taiwan.

But Purugganan said he was skeptical of findings that the plant was developed for drug or fiber use 12,000 years ago, as archaeological evidence shows that cannabis use or constant presence for these purposes began about 7,500 years ago. “I would like to see a much larger study with a larger sample,” he said.

Luca Fumagalli, study author and biologist in Switzerland specializing in conservation genetics, said the theory of a Central Asian origin was largely based on observational data from wild samples in that region. region. “It’s easy to find wild samples, but they’re not wild types,” Fumagalli said. “These are plants that have escaped captivity and have re-adapted to the wild. “By the way, that’s why you call it weed, because it grows anywhere,” he added.

The study was led by Ren Guangpeng, a botanist at Lanzhou University in Gansu Province, western China. Ren said in an interview that the origin site of the domestication of cannabis was most likely northwestern China, and this finding could aid current efforts in the country to breed new types of hemp.

To conduct the study, Ren and his colleagues collected 82 samples, seeds or leaves, from around the world. The samples included strains bred for fiber production and others from Europe and North America that were bred to produce large amounts of tetrahydrocannabinol (THC), the most mood-altering compound in the world. plant.

Fumagalli and his colleagues then extracted genomic DNA from the samples and sequenced them in a laboratory in Switzerland. They also downloaded and reanalyzed sequencing data from 28 other samples. The results showed that the wild varieties they analyzed were in fact “historical escapements of domesticated forms” and that the existing strains in China – cultivated and wild – were their closest descendants from the ancestral gene pool.

“Although further sampling of wild plants in these key geographic areas is still needed, our results, which are already based on very large sampling, suggest that the pure wild progenitors of C. sativa have disappeared, ”they wrote. As hemp’s function as a global source of textiles, food and oilseeds dried up in the 20th century, the use of cannabis as a recreational drug has increased, the new study notes. But there are still “big gaps” in knowledge about its history of domestication, he said, largely because the plant is illegal in many countries.

It can also be difficult to understand precisely how plant species are domesticated in the first place, said Catherine Rushworth, a postdoctoral researcher at the University of Minnesota who studies the evolution of plants. Although scientists can make basic predictions of how a given plant species will diverge in nature, she added, such predictions “go out the window” when a process of natural selection is driven by. humans. “So, for example, we might think that species would diverge as they adapt to different habitats or different pollinators,” she said. “But people are often the pollinators and people have created these habitats.

This article originally appeared in The New York Times.

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