The Revolutionary Genius of Plants by Stefano Mancuso

Author:Stefano Mancuso
Language: eng
Format: epub
Publisher: Atria Books

Turtles from the Galápagos islands and Mauritius were once among the most important transporters and diffusers of seeds on their respective islands.

CHEMICAL MANIPULATION

The example of the chili pepper and its alkaloid is hardly an isolated case. Many chemical compounds of plant origin affect the functioning of the brain, and the mechanisms through which these psychoactive molecules operate are well explained. What is not clear is why compounds produced by plants have an effect on the brains of animals. Indeed, why should plants spend energy on producing molecules that cause effects on the brains of animals?

The current neurobiological theories about drug use are based on the observation that all molecules that are addictive activate an area of the brain involved in managing the reward system. Every time we do something useful for our survival, this ancient area of the brain—which evolved to activate in response to stimuli, such as food, water, and sex—rewards us with pleasure, thus causing us to repeat the action. Acting on the same system, the drugs induce us to repeat the consumption of the molecule that triggered the reward system, thus creating dependency.

Yet all the hypotheses on the origin of plant-based drugs consider the main alkaloids (caffeine, nicotine, and so on) as neurotoxins that were developed to punish and deter herbivores. According to this theory, evolution should not have produced compounds that, acting on the reward system, increase the consumption of the plant. In an ecological context, this apparent contradiction is known as the “drug-reward paradox.” However, if we accept the idea that the neuroactive molecules produced by plants are not a mere deterrent but rather a tool with which to attract animals and manipulate their behavior, the paradox is easily resolved by placing the plant-animal interaction in a very different ecological context and opening new angles in the neurobiological search for effective tools to combat drug abuse. Going back, therefore, to the extrafloral nectar at the beginning of the chapter, the relationship between plants and ants and their long history of coevolution offers the ideal model on which to test this hypothesis. And if, as I believe, we can show that even in the interaction with ants, the production of neuroactive molecules is used by plants to manipulate their behavior, we will have further evidence of this not inconsiderable ability, which would radically change our image of plants from simple beings, passively at the mercy of animal needs, to complex living organisms capable of manipulating the behaviors of others—a notable reversal of roles.

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