The perception of taste and flavour (a combination of taste, smell, and chemesthesis), here also referred to as chemosensation, enables animals to find high-value foods and avoid toxins. Humans have learned to use unpalatable and toxic substances as medicines, yet the importance of chemosensation in this process is poorly understood. Here, we generate tasting-panel data for botanical drugs and apply phylogenetic generalised linear mixed models to test whether intensity and complexity of chemosensory qualities as well as particular tastes and flavours can predict ancient Graeco-Roman drug use. We found chemosensation to be strongly predictive of therapeutic use: botanical drugs with high therapeutic versatility have simple yet intense tastes and flavours, and 21 of 22 chemosensory qualities predicted at least one therapeutic use. In addition to the common notion of bitter tasting medicines, we also found starchy, musky, sweet, and soapy drugs associated with versatility. In ancient Greece and Rome, illness was thought to arise from imbalance in bodily fluids or humours, yet our study suggests that uses of drugs were based on observed physiological effects that are often consistent with modern understanding of chemesthesis and taste receptor pharmacology.
Keywords: chemosensory perception; ethnobiology; ethnopharmacology; evolutionary biology; herbal medicine; history of medicine; medicine; none; taste of medicine.
In ancient times people used trial and error to identify medicinal plants as being effective. Later, diseases were believed to arise from imbalances in body fluids (or ‘humours’), and botanical drugs were thought to restore this balance through the power of their taste. Modern science rejects this theory but does recognise the importance of chemosensation – our sensitivity to chemicals through taste and smell. These senses evolved in humans to help us seek out nutrients and avoid toxins and may also have guided the ancient uses of botanical drugs. There are many records of historical medicinal plant use and ailments, which makes it possible to explore possible relationships between therapeutic uses of botanical drugs and their chemosensory qualities. To investigate if therapeutic uses of botanical drugs could indeed be predicted by taste and flavour, Leonti, Baker et al. collected 700 botanical drugs identified in an ancient text, named De Materia Medica, which dates back to the 1st century CE. The researchers asked volunteer tasters to classify the botanical drugs using 22 taste descriptions, such as bitter, aromatic, burning/hot, and fresh/cooling. The volunteers were also asked to score the strength of these tastes. Leonti, Baker et al. then used statistical modelling to see if the participant’s taste descriptions could be used to predict the therapeutic uses of the drugs identified in the ancient text. This revealed that of the 46 therapeutic indications described in the text, 45 showed significant associations with at least one taste quality. Botanical drugs with stronger and simpler tastes tended to be used for a wider range of therapeutic indications. This suggests that chemosensation influenced therapeutic expectations in ancient, prescientific medicine. The study of Leonti, Baker et al. brings ancient medicine to life, offering valuable insights into the chemosensory aspects of medicinal plants and their potential applications in modern medicine. A next step would be to explore whether these insights could have relevance to modern science.
© 2023, Leonti et al.