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All the substances that are the main drugs of abuse today originate in natural plant products and have been known to human beings for thousands of years. Opium, the basis of heroin, is an extract of the Asian poppy Papaver somniferum. Four thousand years ago, the Sumerians and Egyptians were already familiar with its usefulness in treating pain and diarrhea and also with its powers to affect a person’s psychological state.
Cocaine is an extract of the leaves of Erythroxyolon coca, a small tree that thrives on the eastern slopes of the Andes in western South America. Amazon Indians chewed coca long before the Conquest, as an antidote to fatigue and to reduce the need to eat on long, arduous mountain journeys. Coca was also venerated in spiritual practices: Native people called it the Divine Plant of the Incas. In what was probably the first ideological “War on Drugs” in the New World, the Spanish invaders denounced coca’s effects as a “delusion from the devil.”
The hemp plant, from which marijuana is derived, first grew on the Indian subcontinent and was christened Cannabis sativa by the Swedish scientist Carl Linnaeus in 1753. It was also known to ancient Persians, Arabs and Chinese, and its earliest recorded pharmaceutical use appears in a Chinese compendium of medicine written nearly three thousand years ago. Stimulants derived from plants were also used by the ancient Chinese, for example in the treatment of nasal and bronchial congestion.
Alcohol, produced by fermentation that depends on microscopic fungi, is such an indelible part of human history and joy making that in many traditions it is honoured as a gift from the gods. Contrary to its present reputation, it has also been viewed as a giver of wisdom. The Greek historian Herodotus tells of a tribe in the Near East whose council of elders would never sustain a decision they made when sober unless they also confirmed it under the influence of strong wine. Or, if they came up with something while intoxicated, they would also have to agree with themselves after sobering up.
None of these substances could affect us unless they worked on natural processes in the human brain and made use of the brain’s innate chemical apparatus. Drugs influence and alter how we act and feel because they resemble the brain’s own natural chemicals. This likeness allows them to occupy receptor sites on our cells and interact with the brain’s intrinsic messenger systems. But why is the human brain so receptive to drugs of abuse?
Nature couldn’t have taken millions of years to develop the incredibly intricate system of brain circuits, neurotransmitters and receptors that become involved in addiction just so people could get “high” to escape their troubles or have a wild time on a Saturday night. These circuits and systems, writes a leading neuroscientist and addiction researcher, Professor Jaak Panksepp, must “serve some critical purpose other than promoting the vigorous intake of highly purified chemical compounds recently developed by humans.” Addiction may not be a natural state, but the brain regions it subverts are part of our central machinery of survival.
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