Science commentary
Cannabis confusions
Debates about cannabis are not confined to its value as a medicine or to its possible hazards as a recreational drug.1 Something much more fundamental has been engaging the experts for years: its taxonomy. Are all plants belonging to the genus Cannabis mere varieties of a single species—or is it correct to recognise at least three separate species?
In his original 1753 classification, Carl Linnaeus identified just one, Cannabis sativa. The first indication of dissent came in 1785 when another eminent biologist, Jean-Baptiste Lamarck, was given some plant specimens collected in India. On the basis of several characteristics including their firm stems, thin bark, and the shape of their leaves and flowers, Lamarck felt that they should be distinguished from C sativa. Accordingly he invoked a new species, C indica.
In a lengthy and detailed review of the cannabis species problem, Ernest Small of the Canadian Biosystematics Research Institute commented that Lamarck seems to have reached his decision after “relatively little study.”2 He adds that “in the ‘exploratory age’ of plant taxonomy scientists often were forced to come to conclusions on the basis of very limited material.”
The third and least well founded species is C ruderalis. This was the name that a Russian, Janischevsky, gave to the cannabis plants he found growing in the south eastern central region of his country. The differences he noted were mostly in the size, shape, and casing of the seeds. And even Janischevsky himself seems not to have been totally convinced that these justified a new species.
Debates among “splitters” and “lumpers” over the correct classification of Cannabis rumbled on for much of the last century, although the lumpers seem to have won the majority vote. One commonly expressed opinion is that indica, ruderalis, and other so-called species should be regarded as no more than sub-species or even variants of C sativa.3
More recently, haplotype analyses of mitochondrial and chloroplast DNA from 196 cannabis samples seized by the Australian police, has led to another subgroup dubbed (so far unofficially) rasta.4 What are we to make of this addition to the fold? Not very much, in all likelihood—except a further indication that nature has little regard for human attempts to categorise it.
Potency
Equally unhelpful are the scores of names by which the users of marijuana refer to their drug. Terms such as bhang, blow, pot, weed, dope, grass, ganja, hash, etc, bear less relation to botanical science than to the user’s culture, the material’s geographical origin and concentration, and methods of preparation, delivery, or use. The many websites devoted to cannabis carry subjective accounts of the various effects of the different varieties; but scientifically reliable data on the quantity of tetrahydrocannabinol—the main psychoactive ingredient in cannabis—is predictably sparse.
One organisation that publishes potency figures bearing some relation to botanical nomenclature is the Independent Drug Monitoring Unit, a research company specialising in data on UK drug use. Thus Big Bud, an indica-sativa hybrid is said to be 2-12% tetrahydrocannabinol by dry weight5 and Haze, a late flowering sativa variety, is usually 6% or more. Skunk, originally another indica-sativacross, comes out at 10-12%, although the label skunk now tends to be applied to any powerful strain of herbal cannabis.
What’s in a name?
Besides professional taxonomists, and possibly dealers, who cares how Cannabis plants are classified? Lawyers, it seems. When a Californian court convicted John Anthony Van Alstyne of selling marijuana6 he appealed on several grounds, including the legal definition of the word. His advisers maintained that the term “marijuana,” as used in Californian statutes, referred only to material from C sativa. They argued that there was “no evidence that the marijuana involved in his case was Cannabis sativa L as opposed to one of the other species.”
The judges accepted the appellant’s claim that even experts couldn’t agree over the Cannabis species. That said, they went on to point out that the basis of the appeal was, in essence, that when the legislature had passed the law on marijuana it “meant to outlaw the euphoric effect of the sativa L species but not the effect of other species.” To suggest it had any such intention, declared the judges, would be absurd. They therefore concluded that, while the aim of the law was perfectly clear, scientific advance had rendered its wording obsolete. Denying Van Alstyne his appeal, they added that the statute had become “a potential trap for the unwary, and the legislature would be well-advised to rewrite the section so that it plainly says what it means.”
Against a background of such fundamental ambiguity it is unsurprising to find epidemiologists and neuropharmacologists concluding that the issue is “likely to remain contentious.”1 Proponents of legalisation and banning confront each other through a pungent haze of smoky uncertainty.
References
