There exists an alternate structure of taxonomy for cannabis which has not been adopted by our culture, yet appeals to the scientific community. This taxonomic structure goes against the grain of what we're used to hearing: sativa is an upper and indica is a downer. What if that were too simplistic? What if we've been saying it wrong? You can hardly blame our ignorance given that the US government has intentionally supressed the scientific inquiry of cannabis by disallowing studies to be accepted outside of the federal compound that cultivates marijuana in Mississippi. That only recently ended in 2016. Our common knowledge on this matter is therefore inadequate. The recent statements by the Whitehouse on medical marijuana and the fact that the US Department of Health and Human Sciences holds a patent on non-pyschoactive cannabis sativa (6,630,507) with the claim that cannabis can be used as "a method of treating diseases caused by oxidative stress," should give cause for us to have a more educated discussion on naming what we smoke.
Robert C. Clarke and Mark D. Merlin, authors of Cannabis Evolution and Ethnobotony (2013) posit that the taxonomy of cannabis is broken down into three sub-species: cannabis sativa (includes narrow leaf hemp, feral and non-feral), cannabis indica (includes narrow-leaf drug, broad-leaf drug, broad-leaf hemp, feral and non-feral), and possibly a third genus called cannabis ruderalis (anciently used for seeds and fiber in central Asia). This differs from our understanding of what sativa and indica really mean. These scientists claim that the genus sativa is for non-pyschoactive plants like hemp and only indica refers to pyschoactive cannabis. They break down each species into two groups, feral (wild) and non-feral (human cultivated). Over thousands of years, various cultivars have spread across the continents from human interference, whether done purposefully or by accident. These scientists have traced the geographic areas in which various species of cannabis eminated and make theories on how they evolved based on ethnobotnic evidence. Geneticist Mowgli Holmes, cofounder and Chief Science Officer of Phylos Bioscience believes that the popular nomenclature is meaningless because of the never ending hybridization of various phenotypes.
It's extremely difficult to trace the history of various species of cannabis because we don't know if it grew spontaneously or if it was cultivated and then released into the wild. Think of all the cross-breeding and selection processes used by our ancestors to get the desired characteristics of the plant, whether their goal was to select a stronger hemp fiber or a more potent hallucinogen for ceremonial purposes. We have various accounts of explorers identifying certain species of cannabis as they traveled throughout Africa and Asia, which allowed scientists to corroborate their findings, but this is essentially the basis of our ethnobotnic understandings and so much has changed since early discovery.