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The evolution of drug abuse
- By News Services
- Published 03/24/2008
- Understanding Addiction
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World Science
A new study proposes that humans and other animals have a long evolutionary relationship with brain-influencing drugs.
New research challenges traditional accounts of why we wallow in chemical gratification
Why do people abuse drugs? It’s not only a question worried parents ask their wayward, substance-dabbling teenagers. It’s also a deeper question asked by biologists.
In general, nature has designed all creatures as exquisite machines for their own protection and propagation. Yet we’re easily and often drawn into self-destruction by nothing more than lifeless chemical lures. This weakness seems such a jarring exception, such a dismal Achilles’ heel, that it calls out for explanation.
Scientists typically offer the following one. Drugs are chemicals that inappropriately trigger activity in brain circuits designed for very different purposes: to provide a sense of reward for having satisfied ordinary needs, healthfully.
The brain has few defenses against this chemical deception, the standard account goes, because drugs were unknown in the natural environment that shaped human evolution.
This traditional view, though, is coming under attack. A new study proposes the brain evolved to account for and even exploit drugs. Although their abuse is still unhealthy, the authors suggest it’s wrong to think they cheat the brain in the sense traditionally theorized.
“Evidence strongly indicates that humans and other animals have been exposed to drugs throughout their evolution,” wrote the scientists in the study.
The research, by anthropologist Roger Sullivan of California State University and two colleagues, appeared March 19 online in the journal Proceedings of the Royal Society B: Biological Sciences.
The most popular drugs of abuse are plant toxins that evolved to protect plants from predators, as evolutionary biologists have “convincingly argued,” Sullivan and colleagues wrote.
For example, nicotine, the key addictive ingredient of cigarettes, helps ward off an array of insects, mammals and other creatures from munching on tobacco plants. Further evidence of the fundamentally poisonous nature of drugs of abuse, the three scientists argued, is that first-time users often report unpleasant reactions.
Since plants long predate humans, the presence of these substances in plants would seem to indicate we and our ancestors have long dealt with them, the researchers continued.
But further evidence of this, they added, is in our own makeup. All animals produce molecules known as cytochromes, whose functions include detoxifying ingested plant poisons. Cytochromes that specifically neutralize brain-affecting plant toxins have remained a consistent feature of human evolution, Sullivan and colleagues wrote.
All this shows “our ancestors were regularly exposed to plant neurotoxins,” they added, so the view of our brains as unsuspecting victims of the new chemical threat is untenable.
It remains unclear what might be the true evolutionary explanation of drug abuse, they wrote: the “paradox” stays of why substances designed as poisons, are pleasurable to so many.
One possibility, the scientists suggested, is that animals co-opted some plant toxins and used them for their own defenses against parasites. If this is true, then evolution, the process by which species adapt and change to meet environmental demands, might have designed our brains to encourage some drug use. This could involve shaping our brains to associate drug intake with feelings of reward. “But there are, of course, other possibilities,” the researchers wrote.
World ScienceMarch 21, 2008
A new study proposes that humans and other animals have a long evolutionary relationship with brain-influencing drugs.
New research challenges traditional accounts of why we wallow in chemical gratification
Why do people abuse drugs? It’s not only a question worried parents ask their wayward, substance-dabbling teenagers. It’s also a deeper question asked by biologists.
In general, nature has designed all creatures as exquisite machines for their own protection and propagation. Yet we’re easily and often drawn into self-destruction by nothing more than lifeless chemical lures. This weakness seems such a jarring exception, such a dismal Achilles’ heel, that it calls out for explanation.
Scientists typically offer the following one. Drugs are chemicals that inappropriately trigger activity in brain circuits designed for very different purposes: to provide a sense of reward for having satisfied ordinary needs, healthfully.
The brain has few defenses against this chemical deception, the standard account goes, because drugs were unknown in the natural environment that shaped human evolution.This traditional view, though, is coming under attack. A new study proposes the brain evolved to account for and even exploit drugs. Although their abuse is still unhealthy, the authors suggest it’s wrong to think they cheat the brain in the sense traditionally theorized.
“Evidence strongly indicates that humans and other animals have been exposed to drugs throughout their evolution,” wrote the scientists in the study.
The research, by anthropologist Roger Sullivan of California State University and two colleagues, appeared March 19 online in the journal Proceedings of the Royal Society B: Biological Sciences.
The most popular drugs of abuse are plant toxins that evolved to protect plants from predators, as evolutionary biologists have “convincingly argued,” Sullivan and colleagues wrote.
For example, nicotine, the key addictive ingredient of cigarettes, helps ward off an array of insects, mammals and other creatures from munching on tobacco plants. Further evidence of the fundamentally poisonous nature of drugs of abuse, the three scientists argued, is that first-time users often report unpleasant reactions.
Since plants long predate humans, the presence of these substances in plants would seem to indicate we and our ancestors have long dealt with them, the researchers continued.
But further evidence of this, they added, is in our own makeup. All animals produce molecules known as cytochromes, whose functions include detoxifying ingested plant poisons. Cytochromes that specifically neutralize brain-affecting plant toxins have remained a consistent feature of human evolution, Sullivan and colleagues wrote.
All this shows “our ancestors were regularly exposed to plant neurotoxins,” they added, so the view of our brains as unsuspecting victims of the new chemical threat is untenable.
It remains unclear what might be the true evolutionary explanation of drug abuse, they wrote: the “paradox” stays of why substances designed as poisons, are pleasurable to so many.
One possibility, the scientists suggested, is that animals co-opted some plant toxins and used them for their own defenses against parasites. If this is true, then evolution, the process by which species adapt and change to meet environmental demands, might have designed our brains to encourage some drug use. This could involve shaping our brains to associate drug intake with feelings of reward. “But there are, of course, other possibilities,” the researchers wrote.
World ScienceMarch 21, 2008
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1 Response to "The evolution of drug abuse"
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said this on 08 Apr 2008 2:33:16 AM EDT
Drugs come from plants and later were synthesized so patents could be added to make more money. Opium was used for pain, diarrea, coughs and worked fine used in moderation. The same goes for stimulents used in their place in moderation. There are others from tree bark for asparine like effects. .......Just as an example chronic pain could be treated with opium and the side effects would be much less and it is much harder to overdose. Just a thought!
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