The history of medical cannabis is quite long: Humans have been using marijuana to cure headaches and chronic pain, as an anesthetic, and to treat wounds throughout the majority of human existence. In ancient China and Taiwan, surgeons used cannabis as an anesthetic during surgery; in Egypt, it was used to relieve hemorrhoid pain.

It shouldn’t be surprising, then, that new research suggests that hunter-gatherer tribes used cannabis as a way to unconsciously stave off intestinal worms. The study, conducted by Washington State University anthropologists, examined cannabis use among Aka foragers — a group of people in Central Africa who are known as tropical forest foragers — in order to see whether people outside of the Western way of thinking used the drug therapeutically.

“In the same way we have a taste for salt, we might have a taste for psychoactive plant toxins,” Ed Hagen, an anthropologist at Washington University Vancouver and an author of the study, said in the press release. “So we thought, ‘Why would so many people around the world be using plant toxins in this very recreational way?’ If you look at non-human animals, they do the same thing, and what a lot of biologists think is they’re doing it to kill parasites.”

They analyzed 400 adult Aka who lived near the Lobaye River in the Central African Republic, finding that 70 percent of the males and six percent of the females used marijuana. Next, they sampled stool from the participants to measure helminth infections — and found that 95 percent of them contained the infection. Interestingly, the people who used cannabis had lower rates of infection than those who didn’t use the drug.

It’s important to note that this study was conducted by anthropologists acting on assumption. There’s no evidence yet to suggest that the Aka foragers used the drug because of its medicinal benefits, or if it was simply a correlation. In addition, researchers still aren’t sure whether cannabis can treat parasites and worms. In a previous study, author Ed Hagen and a team of researchers found that cannabis can kill worms in a petri dish, but it hasn’t been proven to work in humans yet.

Their study might be a long stretch, but one thing is clear: Cannabis has been an integral part of human religion, spirituality, and civilization for thousands of years. It’s considered entheogenic, or a substance that is used for religious, shamanic, or spiritual reasons (such as meditation, enlightenment, or celebrating holidays). And it's very likely that humans have been using it for medicinal purposes as well, though we need to fund the research to fully understand how it works therapeutically.

Source: Roulette C, Kazanji M, Breurec S, Hagen E. High prevalence of cannabis use among Aka foragers of the Congo Basin and its possible relationship to helminthiasis. American Journal of Human Biology. 2015.