Posted by Mike Ives; Joy Dong and Maria Cramer contributed to the coverage.
People who feel the effects of marijuana tend to what scientists call “divergent thinking,” the process of finding solutions to a loosely defined question. Here’s a question to think about: where do the weeds come from? No, not where it was bought, but where and when the plant was domesticated for the first time.
Many botanists believe that the cannabis sativa plant was first domesticated in Central Asia. But a study published Friday in Science Advances suggests that East Asia is the more likely source and that all existing strains of the plant come from a “genetic gene pool” represented by wild and cultivated strains growing in China today.
The study authors found that the plant was a “primarily multi-purpose plant” that was grown about 12,000 years ago in the early Neolithic, likely for fiber and medicinal purposes.
Farmers began breeding the plant specifically for its mind-altering properties about 4,000 years ago when cannabis spread across Europe and the Middle East, according to the study’s authors.
Previously, the domestication history of #cannabis wasn’t well understood – largely due to legal restrictions – but a new study suggests the plant has its earliest roots in what is now northwestern China. https://t.co/5mV564TzXb pic.twitter.com/6gHcAUYiiV
– Science Advances (@ScienceAdvances) July 19, 2021
Michael Purugganan, a professor of biology at New York University who read the study, said the common assumption about early humans is that they domesticated plants as food. “That seemed to be the most pressing problem for humans at the time: How do you get food,” said Purugganan, who was not involved in the research. “It is interesting to note that they also dealt with fiber and even intoxicants very early on. It would call into question the priorities of these Neolithic societies.
A 2016 study by other scientists said the earliest records for cannabis were mostly from China and Japan, but most botanists believe it was likely first domesticated in eastern central Asia, where wild varieties of the plant are widespread.
Genetic sequencing for the latest study suggests the species has a “single origin of domestication” in East Asia, the researchers wrote. By sequencing genetic samples from the plant, they found that the species was most likely domesticated in the early Neolithic. They said their conclusion is supported by pottery and other archaeological evidence from the same period discovered in what is now China, Japan, and Taiwan.
But Purugganan said he was skeptical of the conclusions that the plant was developed for drug or fiber consumption 12,000 years ago, as archaeological evidence shows the consistent use or presence of cannabis for these purposes some 7,500 years ago. “I would like a much larger study with a larger sample,” he said.
Luca Fumagalli, author of the study and a biologist in Switzerland who specializes in conservation genetics, said the theory of Central Asian origin is largely based on observational data from wild samples in that region. “It’s easy to find wild specimens, but they’re not wild types,” said Fumagalli. “These are plants that have escaped captivity and adapted again to the wild environment. “That’s why you call it grass, by the way, because it grows all over the place,” he added.
The study was led by Ren Guangpeng, a botanist at Lanzhou University in western China’s Gansu Province. Ren said in an interview that the original location of cannabis domestication was most likely in northwest China and that the discovery could help in the country’s current efforts to breed new strains of hemp.
To conduct the study, Ren and colleagues collected 82 samples, either seeds or leaves, from around the world. Samples included strains selected for fiber production and others from Europe and North America bred to produce high levels of tetrahydrocannabinol (THC), the plant’s most mood-altering compound.
Fumagalli and his colleagues then extracted genomic DNA from the samples and sequenced them in a laboratory in Switzerland. They also downloaded and re-analyzed sequencing data from 28 other samples. The results showed that the wild varieties they analyzed were indeed “historical escapes from domesticated forms” and that existing varieties in China – cultivated and wild – were their closest offspring of the ancestral gene pool.
“Although additional sampling of wild plants is still required in these key geographic areas, our results, which are already based on very broad sampling, would suggest that pure wild ancestors of C. sativa are extinct,” they wrote As Hemp’s function as a The global source of textiles, food and oilseeds dried up in the 20th century, and recreational cannabis use increased, according to the new study. However, there are still “large gaps in knowledge” about their domestication history, mainly because the plant is illegal in many countries.
It can also be difficult to understand exactly how plant species are domesticated in the first place, said Catherine Rushworth, a postdoctoral researcher at the University of Minnesota who studies plant evolution. Although scientists can make some basic predictions about how a given plant species will diverge in nature, she adds that such predictions “go out the window” when a natural selection process is driven by humans. “For example, we might think that species would diverge as they adapt to different habitats or different pollinators,” she said. “But humans are often the pollinators, and humans created these habitats.
This article originally appeared in the New York Times.