Long before humans first appeared, this profuse natural pharmacopeia encouraged an equally wide variety of drug-seeking behaviours. Many animals root out and consume plant drugs for medical purposes - to poison intestinal parasites, for example - but there are also abundant examples of the deliberate pursuit of intoxication. Cats abandon themselves to the ecstasy of catnip, which has little effect on humans but causes felines to head-twitch, salivate, give love-bites and apparently experience sexual hallucinations: in the wild, the plant may perform the function of bringing females into heat. Siberian bears and reindeer seek out fly agaric mushrooms and appear to relish their mind-altering effects. Migrating birds make regular seasonal detours to gorge on fermented fruits. For many villages across the Indian subcontinent, a herd of drunken elephants on the rampage after feasting on rotten windfalls or raiding illegal stills is an all too familiar hazard. Our closest relatives, the primates, display many sophisticated drug-seeking behaviours. Baboons chew tobacco in the wild, and apes in captivity readily learn the habit of smoking it. Male mandrills in Gabon have even been observed to dig up and eat the hallucinogenic iboga root, then wait for an hour for its effects to take hold
Before engaging rivals in combat.
In many human cultures, the origin stories of plant-derived drugs involve tales of people observing and copying the habits of animals. In Ethiopia, for example, the discovery of coffee is attributed to goatherders who observed their flock becoming frisky and high-spirited after consuming coffee beans. Goats are very fond of coffee, and modern plantations must be robustly fenced against them; their taste for the effects of caffeine may have prompted the plant, which spreads its seeds via animal droppings, to produce it. Theirs is a long-standing symbiosis, though human participation in the cycle is relatively new. The practice of coffee drinking seems only to have developed around the tenth century AD-recently enough, perhaps, for the legends of its discovery to have some historical validity. It seems plausible that the practice of roasting the seeds of one among many hard, bitter and inedible desert shrubs and then percolating boiling water through them might have emerged only in modern times, and with some peculiar prompting.
Monkeys ‘aping’ the new habit of tobacco smoking was a popular theme of seventeenth-century prints, such as this engraving after the Flemish artist David Teniers the Younger. Apes and monkeys use a particularly wide range of intoxicants, and are easily taught to smoke tobacco in captivity. (Wellcome Library, London)
Plants, then, use their drugs to nudge and manipulate the animal kingdom, repelling some species and attracting others; but what benefits do animals derive from drugs? It is often assumed that they consume them instinctively for chemical rewards: the stimulation of neurochemicals such as dopamine and serotonin, and the pleasurable sensations they deliver to the brain. Indeed, the modern neurological understanding of drugs leans heavily on the responses of laboratory animals: the ‘addictiveness’ of substances such as cocaine and opiates is measured by, for example, how many times a caged rat will press a lever to receive a dose. But there is more to animal drug-taking than reflex response. Environment is also a factor: many animals, for example, are more inclined to take drugs in captivity. This tendency was explored in a startling series of experiments by the Canadian addiction psychologist Bruce Alexander.
Alexander’s clinical work involved tests on laboratory rats. Initially the rats were kept individually in small cages with two drinking bottles, one containing plain water and the other morphine solution, which were weighed daily to generate behavioural data. But Alexander became curious about the effects of environment, and constructed alongside the cages a habitat that became known as Rat Park. Several rats, who are naturally gregarious, were housed together in a large vivarium enriched with wheels, balls and other playthings, on a deep bed of aromatic cedar shavings and with plenty of space for breeding and private interactions. Pleasant woodland vistas were even painted on the surrounding walls.
In Rat Park, he discovered, drug use diminished markedly: some rats reduced their morphine intake to one-twentieth that of their caged neighbours. Even if pre-addicted to morphine, they would suffer withdrawals rather than maintain their habit. When the morphine water was sweetened with sugar, most of the rats still chose plain water, though they would drink the sugared water if Alexander also added naloxone, which blocks morphine’s effects. It seemed that the standard experiments were measuring not the addictiveness of opiates but the stresses inflicted on lab rats caged in solitary confinement, with catheters inserted into their jugular veins.
The Rat Park experiments conducted by Bruce Alexander in the late 1970s at Simon Fraser University in British Columbia, Canada. Some of the laboratory rats typically housed in cramped and solitary cages (left) were moved to a spacious, open-plan social environment (right), where their drug use diminished dramatically. (Courtesy Bruce Alexander)
Such experiments do not disprove the claim that animals take drugs for their chemical rewards, but they do indicate that the impulse to take drugs is more than a simple behavioural reflex. In humans, of course, the variables become far more complicated. Sensory pleasure is an obvious component of most drug use, though the definitions of pleasure are as varied as human culture itself. But some drugs offer strictly functional benefits. The ability to alter consciousness in dramatic but controllable ways has many uses, and there is much evidence to suggest that humans have long used such drugs instrumental!/: even, in some cases, elaborating their entire social systems around the heightened states of consciousness such substances produce.
World History
