By Emily Ledger
Most people will realise that – far from an inconsequential crop that only gained popularity due to its coincidental ability to get us ‘high’ – the cannabis plant has been an important part of many human societies for millennia. Twelve millennia, to be more precise, according to recent findings.
A recent analysis of the genomes of 110 plants from around the world, has found that cannabis was first domesticated in what is now northwest China around 12,000 years ago. This finding confirms cannabis as one of the oldest cultivated plants in history.
The original domestication of the crop is believed to have been a result of the many uses of many parts of the plant. For example, abundant evidence collected from various archaeological sites from across the world shows that cannabis, or hemp, has been used for many things, including fibre for clothing and weapons, food and oil, medicines, and even as a spiritual and religious tool.
Despite the plant’s long history in human culture, access to cannabis is still largely restricted – making the research necessary to discover the domestication date of the crop with its difficulties.
According to Luca Fumagilli from the University of Lausanne in Switzerland – one of the researchers who worked on the analysis, it was hard to get hold of the strains from around the world that were needed for the genetic study: “You can’t just go and collect samples because you go to jail,” he explained.
Nonetheless, Fumagilli collaborated with researchers from all over the planet to collect and sequence 80 different strains of cannabis that were either cultivated by farmers or grew in the world. The data collected from this research was added to the 30 previously sequenced genomes included in the analysis.
While the original wild ancestor of cannabis is believed to be extinct, the researchers found that strains growing in northwest China today are its closest living relatives. The findings of genome sequencing are supported by existing archaeological evidence, including pottery with hemp cord markings that are also believed to date from around 12,000 years ago.
However, the crop isn’t believed to have been bred selectively by farmers until around 4,000 years ago. At this point, farmers are thought to have chosen particular strains of cannabis that had distinct features that would make them suitable for a specific use – for example, for fibre production or medicinal use.
The team of researchers identified a number of the genetic changes brought about by this selective period over a long period of time. For example, according to the study, “several genes bearing signals of positive selection in hemp-type–improved cultivars are involved in inhibiting branch formation, associated with flowering time and photoperiodism and involved in cellulose and lignin biosynthesis.”
These genetic changes, believed to have been brought about by selective breeding by farmers, resulted in plants growing taller and having more fibre in their stems.
On the other hand, in strains that have proven to be more valuable for their medicinal properties, the researchers identified mutations that resulted in shorter plants with more flowers. These changes are seen to maximise resin production – the part of the plant that is particularly high in cannabinoids.
Strains that are commonly used for medicinal and recreational purposes also have been identified as having many other mutations that boost the production of tetrahydrocannabinol (THC) – the most common cannabinoid that causes a ‘high’ when consumed.
Despite the incredibly long-standing relationship between humans and cannabis, the crop fell out of favour relatively recently due to a number of developments.
The boom of industry in the 19th and 20th centuries offered us a growing portfolio of synthetic fibres, able to replace those derived from the crop. However, the prohibition of cannabis was almost the nail in the coffin for cannabis – including low-THC hemp – for almost a century.
However, the general population, as well as the medical and scientific communities, are increasingly showing an interest in the diverse potential of the ancient crop. In some places, this curiosity is even beginning to end cannabis prohibition and expand production – but we still have a long way to go.