The Origins of Cannabis: Diverse Theories

Since the cannabis plant was first classified by botanists in the 16^th century, numerous theories have been proposed for its origins. The debate continues; the issue is not yet settled and agreed on by all botanists despite the enormous amount of work that has gone into scientific research.

In the last twenty years or so, several different theories have emerged. In this blog, we will examine the main theories about the origins of cannabis that have been historically proposed.

The First Botanical Identifications of Cannabis Sativa

Although the cannabis plant was described by several Greco-Roman authors, in more recent times, the botanical classification began in 1542 with the identification and image of Cannabis sativa (‘cultivated cannabis’) in a work on plants (De Historia stirpum commentarii insignes) by the German physician and botanist Leonhart Fuchs (Russo 2007:1616).

However, the name ‘Cannabis sativa’ was actually coined by Ermolao Barbaro between 1480 and 1490 but only published twenty-three years after he died (McPartland and Small 2020:82).

More than 200 years later, Carl Linnaeus, the Swedish ‘father’ of modern botanical classification, also identified Cannabis sativa from specimens growing in Holland and Sweden (Stearn 1975:17) in his 1753 compendium Species Plantarum. Linnaeus assumed that the centre of origin of cannabis was in India Orientali, encompassing the Indian subcontinent, Southeast Asia, the Malay Archipelago, and Japan (McPartland et al. 2018:635).

These so-called ‘sativa’ varieties of cannabis, studied by Linnaeus in Europe, were psychoactively weak and generally known as ‘hemp’. They were farmed for fibre, rope and cloth on a large scale in Europe, Russia and North America between 1600 and 1920.

The Origins of Cannabis: Theory 1

Jean-Baptiste Lamarck: Europe and India

The classification of cannabis into Cannabis sativa and Cannabis indica began with the Frenchman Jean-Baptiste Lamarck in his Encyclopédie méthodique, published in 1785 (Schultes and Hofmann 1980:88). Lamarck believed that the indica (‘Indian’) variety, known for its distinctive psychoactive properties, is the kind native to India and is different from Cannabis sativa, which grew in Europe, and which he suggested may have also been native to Persia. Cannabis indica, besides being distinctively psychoactive, is shorter, bushier and has broader leaves than Cannabis sativa.

The Unresolved Classification of Cannabis

Lamarck’s influential botanical classification was widely accepted. However, the publication of reports of a third variety of cannabis described by the Russian biologist D. E. Janichevsky in 1924 challenged the earlier binary sativa/indica classification of Lamarck. Janichevsky described Cannabis ruderalis (‘roadside cannabis’), a small (two feet high), dark green, weedy variety found primarily in parts of southern Russia, Siberia, Eastern Europe and Central Asia (Koren et al. 2020:3), making a tripartite classification of the naturally growing cannabis plant (Clarke and Merlin 2013:316ff.).

Cannabis ruderalis, similarly to Cannabis sativa growing in Europe and Russia, was found to be hardly psychoactive at all. It is used neither for fibre or cloth, as it is so small and weedy, nor for intoxication, as it has very low CBD and THC content.

By the 1960s, most botanists had accepted the polytypic classification of the cannabis plant as Cannabis sativa, indica and ruderalis (Schultes et al. 1975:24). However, more recently, some scientists have argued, based on extensive chemotaxonomic, pollen and genetic studies, that all cannabis types derive from one ancestor, Cannabis sativa (Lynch et al. 2017:358; McPartland 2018:209; McPartland and Small 2020; Ren et al. 2021:6). The evidence now seems conclusive, that the simple binary classification of (non-psychoactive) hemp and (psychoactive) marijuana is invalid.

Nevertheless, the issue of how exactly the diversified cannabis plant should be classified remains unresolved. Although cannabis has been of great importance to agricultural and social history, it is presently the only multi-billion-dollar crop without a complete sequence-based genetic linkage or physical genome map (Lynch et al., 2016:351). The classification of types of cannabis, as sketched above, remains one of the most controversial among plant species (see the blog ‘Sativa vs. Indica’).

Besides the issue of classification of types of cannabis, another continually evolving inquiry concerns the origins of the cannabis plant. In the early 21^st century, several new scientific propositions which supersede Lamarck’s theory have been published; these are reviewed below.

Theory 2

Karl Hillig: Afghanistan and Uzbekistan

Nearly twenty years ago, Karl Hillig, who is in the Department of Biology, Indian University, began publishing his pioneering cannabis research. Using both genetic and chemotaxonomic methods, Hillig and his team measured the chemical content of 147 cannabis plant samples from around the world. Hillig endorses the basic, historical, binary classification of sativa/indica and considers ruderalis a possible third original species. He proposes two areas in Asia as the original sources of two main gene pools of cannabis: sativa from Central Asia, around Uzbekistan, and indica from further south, in and around Afghanistan (Hillig 2004:881; 2005:173–176; Hillig and Mahlberg 2004).

Hillig proposes that the two original types of cannabis (sativa and indica) diversified into seven main taxa. The diversification would have resulted from cannabis plants being selectively bred for fibre, cloth, rope, food (from seeds), or psychoactive effects.

Theory 3

Robert C. Clarke and Mark D. Merlin: Caucasus and Eastern China

In a comprehensive study of cannabis by two of the world’s leading experts, Cannabis: Evolution and Botany by Robert C. Clarke and Mark D. Merlin, published in 2013, the researchers maintain, based on the available scientific evidence of the time, that cannabis probably had two main centres of origin, one in Eastern China, and the other in the Caucasus mountains area, which is mostly in what is now Georgia, between the Black Sea and the Caspian Sea.

Map from Clarke and Merlin (2013:125), showing the primary dispersal of cannabis between c. 10,000 and 2,000 BP [before present]

On the map by Clarke and Merlin, it can be seen that there is a putative hemp ancestor (PHA) in the Caucasus region, which they suggest was introduced in the Bronze Age (c. 3200–1600 BCE) by migrants to Europe, where it diverged into the narrow leaf hemp ancestor (NLHA).

Also seen is a putative drug ancestor (PDA), with marked psychoactive properties, in Eastern China. This type, they suggest, diverged into broadleaf hemp (BLH) and a narrow leaf drug ancestor (NLDA), which they maintain probably arrived in India from the eastern Tibet region.

Theory 4

John McPartland: Eastern Asia and Europe

Several botanists in the 19^th and 20^th centuries argued that Europe was the centre of origin of cannabis (McPartland and Hegman 2018:628). Revisiting the question of origins, John McPartland et al. (2018), after extensive work on 479 different pollen samples, propose that besides eastern Asia (see below), cannabis is also indigenous to Europe. A problematic issue with pollen samples of cannabis is that they are very similar to those of hops (Humulus). However, taking this into account, the study indicates (p. 643) that although pollen samples indicating cannabis in the late Miocene period, 6.1–5.3 million years ago, are slightly ambiguous, the oldest pollen samples consistent with cannabis in Europe appeared during the Olduvai cold stage of the earth’s climate, 1.8 million years ago (p. 643). Pollen samples from ten different sites in indicate that cannabis was quite widespread in Europe by 13000 BCE.

Map from McPartland et al. (2018:640), showing evidence of cannabis in Europe, from c. 18,500–15,000 BP [before present] 

McPartland et al. (2018:648) suggest that at least two Copper Age cultures (5500–2700 BCE) in Europe had the potential to domesticate wild cannabis, which is confirmed by pollen samples: the Greek Chalcolithic culture and the Cucuteni-Tripolye culture, which was centred in modern-day Moldova, covering parts of western Ukraine and north-eastern Romania. Subsequently, cannabis has been either found (as seeds) or identified in at least eight Bronze Age cultures (3200–1600 BCE).

In answer to whether or not cannabis was domesticated and cultivated separately from its domestication in eastern China, McPartland et al. believe that it was probable that the cultivation of hemp arose simultaneously and independently in several places (p. 645).

Besides the evidence from pollen samples for the prehistoric flourishing of the plant, the earliest evidence so far for the use and probable cultivation of cannabis by humans comes from Japan, in the Jōmon culture in 8000 BCE, and later in the Yāngsháo culture in China (5000–3000 BCE). The earliest evidence in Europe for cannabis use comes from a site in Moldova dating to 5500­–5000 BCE (McParland and Hegman 2018:627–630).  

Theory 5

Guangpeng Ren et al.: Eastern China

Ren et al. (2021) analyzed the genetic sequences of eighty-two cannabis samples collected worldwide, adding to the sequences of twenty-eight cannabis varieties that had already been profiled (see the blog ‘Cannabis Origins: A Recent Study’). This made a total of 110 varieties that had a full genetic profile. The results indicated that some current Chinese landraces and feral plants represent the closest descendants of the ancestral gene pool from which hemp and marijuana landraces and cultivars have since derived. Ren et al. also observe (p. 3) that the pure, wild progenitors of Cannabis sativa have become extinct.

They propose that cannabis originated in Eastern Asia, where several other important crops, including rice, broomcorn millet, foxtail millet, soybean, foxnut, apricot and peach, were first cultivated. Ren et al. maintain that cannabis subsequently diversified over many centuries, as a consequence of selection for either cloth, fibre, rope, food or for psychoactivity, into four main genetic groups: 1. basal cannabis; 2. hemp-type; 3. feral drug-type; 4. cultivated drug-type.

Genomic dating suggests that both the early domesticated ancestors of hemp and drug types diverged from basal cannabis around 12,000 years ago, in early Neolithic times. The evidence indicates that early domesticated cannabis was initially used for both fibre and psychoactivity until around 4,000 years ago, when there was a strong divergence between fibre and drug types, owing to selective breeding (p. 4).

Where did Cannabis come From? The Conclusion:

In the last twenty years or so, significant progress has been made in tracing the history of the origins, use and cultivation of cannabis. The latest research indicates that eastern China is one region where cannabis most probably originated. However, it also seems certain that cannabis was also indigenous to Europe for many thousands of years. In the 9th century CE that cannabis was introduced to East Africa, and only in the 16^th century did it first reach South America.

References

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