The Origins of Marijuana: Have Researchers Finally Verified It?

Whenever you read about the history of cannabis, you usually discover that it has possibly been used by humans for at least 12,000 years. Hemp rope dated to 30,000+ years ago suggests that it has been used for even longer. However, details on the plant’s origins have proven to be more elusive; until now.

27.8 Million Years in Tibet?

It has long been assumed that weed originated in Central Asia but a study by McPartland, Hegman, and Long, published in Vegetation History and Archaeobotany in May 2019, sought to provide a more precise location. Not only did it appear to succeed, but it also offered a timeline!

The research team analyzed 155 fossil pollen studies in Asia and concluded that the marijuana plant originated in Tibet, some 27.8 million years ago. In a somewhat ironic twist, it appears as if our favorite source of psychoactive activity first grew high above sea level; approximately 3,260 meters to be precise!

Scientists have long sought to pinpoint the location of weed in Central Asia but were unable to do so due to a lack of ancient marijuana in fossil impressions. However, the McPartland team found plenty of fossil pollen representing the Cannabis genus. In the past, analysis of Asian fossil pollen included plants in the Humulus genus. As you may know, this genus is related to weed, and some produce the hops used to make beer.

In this study, the researchers were able to separate the Humulus and Cannabis pollen from the 155 studies and mapped them to various Asian regions to finally discover where Cannabis originated.

For the record, the team identified pollen from Cannabis plants if it was discovered beside other pollen types from the treeless, open habitats where weed is known to grow. They found that the oldest Cannabis fossil pollen placed the genus in China’s northwest from approximately 19.6 million years ago.

However, as Cannabis diverged from the Humulus genus around 27.8 million years ago, it must have originated in a different location. Unfortunately, the McFarland team didn’t uncover any Cannabis pollen from that era. They DID find pollen from another genus of steppe plant known to have grown alongside cannabis at a later date. This pollen from the Artemisia genus was found at the Tibetan Plateau and was dated to 27.8 million years ago.

At this point, the team used educated estimates via a statistical model. As plants such as Artemisia were found with Cannabis in different locations several million years later, it is likely that the plant was also found in Tibet near Qinghai Lake. The main problem is the lack of direct evidence of Cannabis pollen in the region.

An Unprovable Theory?

The general location of marijuana’s origins has been known for over 1,000 years. Hashish was probably discovered by an Arab physician called Ibn Wahshiyah in approximately 930 AD. In his book, On Poisons, he claimed that the odor of weed was lethal! While the physician knew little about the actual effects of weed, he at least knew of its existence. He suggested that it came from India or China.

Few physicians of that era knew much about weed and those that did tended to take their ‘knowledge’ from the famous Roman physician, Claudius Galen, who lived in the second century AD. Galen wrote that if marijuana was consumed in great amounts, it “affects the head by sending to it a warm and toxic vapor.”

Galen didn’t write about the likely origins of marijuana, and it has been the subject of intense debate for a long time. McFarland’s team used precise geographic coordinates for each specimen which were localized to within 0.01 of a degree of latitude and longitude. Ultimately, while the study made an exciting possible discovery, it is arguably impossible to prove it.

Overall, the research team is confident that cannabis’ center of origin is close to Qinghai Lake in the northeastern Tibetan Plateau. According to the study, this “co-localizes with the first steppe community that evolved in Asia.”

The Plateau possibly drove the entire evolution of the plant. Remember, weed thrives in arid, steppe-like environments. It was only the formation of the Tibetan Plateau that promoted the spread of these conditions in Asia.

In case you were wondering, the Plateau was formed when the Asian and Indian landmasses collided. Therefore, the next time you’re cursing the boredom of a plate tectonics lecture, be grateful because it may well be the reason you get to light up after class!

The Spread of Marijuana

According to the study, Cannabis spread west and reached Europe approximately six million years ago. Next, it made its way back east and reached Eastern China around 1.2 million years ago. Cannabis pollen appeared in India before 30,000 BC with archaeological evidence of its existence in Japan 12,000 years ago.

What’s interesting is that Qinghai Lake is a few hundred kilometers from Baishiya Karst Cave. This is significant because archaeologists have found evidence that the Denisovans visited the cave around 160,000 years ago. The Denisovans are a now-extinct species or subspecies of archaic humans in the Homo genus.

It is believed the lineage that developed into Homo sapiens of the anatomically modern variety separated from the lineage that developed into Neanderthals and Denisovans at least 600,000 years ago. Within 300 generations, the Denisovans and Neanderthals diverged from one another in a genetic sense.

In 1980, a Buddhist monk found a partial mandible in the Baishiya Karst Cave. It remained under-researched for 30 years and, in 2019, a research group led by Jean-Jacques Hulin, Fahu Chen, and Dongju Zhang discovered that the fossil from the cave had a ‘close affiliation’ with what was found in the Denisova Cave in Siberia.

Uranium decay dating indicated that it was around 160,000 years old. Does this mean that the Denisovans discovered cannabis long before anyone else? Not necessarily. Hublin points out that the world was in the grip of an ice age at that time. Therefore, we don’t know whether weed could have grown in the Tibetan Plateau in those terrible conditions.

However, cannabis pollen was discovered in the Siberian Denisova Cave. Artefacts found at the cave were dated to around 38,000 BC. Other excavations have found human artifacts which suggest a presence going back 125,000 years! Further research revealed that the Denisova hominin “diverged from a common ancestor” long before modern humans or Neanderthals did; approximately one million years ago!

Final Thoughts on the Origins of Marijuana

We already knew that cannabis had a long and interesting history, even though we only know a fraction of it! This recent discovery only whets the appetite further. Although we may never be able to prove that weed originated in the Tibetan Plateau conclusively, it seems extremely likely.

What is arguably even more fascinating is the possibility that an earlier species may have used the herb long before we did. It makes sense when you think about it: We evolved through curiosity, which led to discovery. The likes of the Denisovans would almost certainly have used the marijuana plant if they found it. The discovery of Cannabis pollen in their Siberian cave suggests they did.

It is possible, perhaps likely, that the first use of marijuana predates what we believe we know.