is there an evolutionary reason for drugs being addictive? do animals get high on them?
I had a cat that would go right to a catnip plant, chew a few leaves, then pass out underneath it regularly.
Back in the 70’s a friend had a Husky named Bosco and anytime a marihuana cigarette was lit in the house - Bosco would come running - he would sit and receive a “shotgun” (blowing the smoke directly into his mouth/nose.) He would also take a paw and knock the flame off of the “roach” and then eat it.
I have heard stories about beer and whiskey drinking dogs but never actually saw one drunk.
Yes, animals can get addicted to substances which addict, particularly opiates and cocaine. Tobacco too, to a lesser extent. They will sacrifice sex and food to obtain them. Both genetics and environment seem to play a role in determining which of a population of test animals will display extreme addictive behavior. (Gosh, just like in people!)
Vast oversimplification:
Certain drugs trigger the ‘reward’ system, which usually only gets triggered for behaviors which are pro-survival, such as obtaining food, water, sex, etc. The drug short-circuits the system, providing gratification while not providing those things needed to sustain life.
i have zero experience with drugs. does it benefit the plant to be addictive? as opposed to being merely tasty?
These things don’t evolve because they are addictive. They evolve because they affect the central nervous system. They are deadly poisonous. Nicotine for example is one of the most tocic substances known to man, with even tiny amounts proving lethal wihtin minutes. There is a good reason why hard drug addicts die from overdoses: too much of the stuff kills them. Humans take in very small measured doses. Anything feeding on the plant takes in very large unmeasured doses. It don’t feed on the plant for long.
No, but we do give them a helping hand by cultivating them. At some point, someone ingested a plant that made them “feel good” or had some sort of healing effect. Once they figured out which plant it was (i.e. coca, opium poppies, tea, coffee, etc), they “unnaturally” gave the plant an evolutionary advantage to be more potent by breeding and selecting for increased potency. Unfortunately, the increased potency usually was coupled with increased addictiveness, so in a manner of speaking, these plants DID evolve because they’re addictive, but that’s not why they came into existance.
As for why these plants make people feel good and relieve pain, that’s more or less coincidence that the alkaloids in them are similar to natural endorphins that bind to pain receptors and block the pain response.
Some good information on the origins of drugs and how exactly they’ve become so widespread can be found in the book Napoleon’s Buttons by Penny LeCouteur and Jay Burreson, both chemists.
Oh I forgot to address this in my post. This statement is quite wrong, at least when referring to alkaloid drugs. The concentration of a drug in the plant is actually quite low, but humans extract it to purify and concentrate the molecule they’re interested in. The reason addicts die is actually the opposite of what you stated, Blake: they take large measured doses as opposed to small unmeasured doses 
To be fair, sometimes the substances are prepared so that they have low doses; nicotine in tobacco is a good example.
Some examples: tea actually has more caffeine than coffee, but the way it’s brewed results in lower dosage per cup.
A quote from the book I cited: “Coca leaves have been used as a stimulant for hundreds of years in the highland areas of Peru, Ecuador and Bolivia. The leaves are mixed with a paste of lime, then tucked between the gum and the cheek, where the alkaloids, released slowly, help counter fatigue, hunger and thirst. It has been estimated that the amount of cocaine absorbed this way is less than half a gram daily, which is not addictive. This traditional method of coca alkaloid use is similar to our use of the alkaloid caffeine in coffee and tea. But cocaine, extracted and purified, is a different matter.” Interestingly enough, cocaine was originally isolated as a treatment for morphine addiction…
Ack. so I’ve danced around the original question… I need to look for the cite, but yes animals can get addicted to drugs. A PhD in physiology told me about a study with monkeys who were given buttons for food, water, and cocaine. The monkeys eventually found the cocaine button and starved to death because that’s all they wanted. Animals just aren’t smart (stupid?) enough to learn chemistry and isolate addictive compounds from plants 
It could be coincidental, but given that the same chemicals have evolved time and again in unrelated plant families and serve little to no purpose within the plant, I think such a belief is less than logical. A more plausible explanation is that the plants have evolved a chemical defence that interacts with animal nervous systems for the very specific purpose of harming the animals. The fact that they mimic animal neurotransmitters etc is not coincidental.
That statement is perfectly accurate particularly when referring to alkaloid drugs. You refer to an example of a person using cocaine as a drug, not an animal eating the plant. An antelope or caterpillar browsing off a coca bush will not mix a leaf with a paste of lime, chew it for a while and spit it out. Such an animal will eat most of the leaves on the plant. This may amount to more than the animal’s body weight. This will of course result in a massive and unmeasured dose of not just cocaine, but a cocktail of other nasty and often synergistic drugs.
erm…, so the plants (in defence) evolved a poison to kill animals by making them come back for more? evil
They did tests with rabbits, where they made them smoke. When not given their scheduled cigarettes, they became anxious and twitchy (well, more so than rabbits usually are).
I can’t find a cite, though.
Errm, let me assure you, if you ate more than 4 grams of nicotine or 8 grams of cocaine you wouldn’t come back for more of anyting ever again. These things are dealy poisonous.
I thought it was first isolated for use as an anesthetic (which it still is used for today) and a stimulant (which it, less legally, still is used for today).
IIRC: Heroin, not cocaine, was developed to replace morphine. They didn’t know heroin would turn out to be even more addictive.
. A more plausible explanation is that the plants have evolved a chemical defence that interacts with animal nervous systems for the very specific purpose of harming the animals. The fact that they mimic animal neurotransmitters etc is not coincidental.
How do you explain certain tryptamines in plants that are not active when taken orally but are extremley potent hallucinogens when processed and then smoked? That would seem to counter the argument that all compounds in plants that can be abused as drugs are there for the protection of the plant although I agree that this is usually the case. Also it was Sigmund Freud who suggested that cocaine could be used to treat morphine addiction, but then again he thought cocaine was a new wonder drug to rival pennicillin and that all men want to shag their mothers so make of it what you will.
I don’t know what you’re referring to, but I’d be inclined to explain it the same way that I explain that theobromine isn’t at all toxic to primates, but will kill a dog at forty paces. Thee things didn’t all, or even primarily evolve, as defences against mammals. Most of them are insecticides. The effects against mammals are either secondary derivations or else co-incidental. Subtle alterations of chemicals induced by heating makes them active.
You have two possibilities don’t you?
Maybe you have found the correct reagents an cooked them up, and the substance was never a drug at all, in which case it doesn’t invalidate any comments concerning the evolution of drugs within plants.
Maybe it can be explained the same way that I explain that theobromine isn’t at all toxic to primates, but will kill a dog at forty paces. These things didn’t all, or even primarily evolve, as defences against mammals. Most of them are insecticides. The effects against mammals are either secondary derivations or else co-incidental. Subtle alterations of chemicals induced by heating makes them active.
Well yes, as with everything in this world if you want to look hard enough I am sure that you will find an exception. By application of the same type of nitpicking approach i deduce that you would never say that humans walk on two legs or that the sun rises in the morning.:dubious:
I expect the poster was referring to DMT ingested via ayahuasca. There is quite a bit of ethnobotanical research on that topic.
Blake, you’ve made a number of increasingly strong arguments but haven’t backed them up with citations.
In particular, I would like to see evidence that it is “given” that these chemicals “serve little to no purpose within the plant”. You would have to know nearly everything about plant biology to make such a claim, and I am unconvinced. I think the most you can say is that their purpose is unknown, in many cases.
Considering that you didn’t know about tryptamines (!), I need more authoritative sources than you have provided so far give your assertions credibility.
Tobacco hornworms eat lots of tobacco.
can anyone explain why THC is present in marijuana? As far as I know that isn’t fatal to anything even insects. Also i’m not nit picking Blake, I am genuinley interested as to why certain plants have chemicals in them that either seem to serve no other purpose other than to get high: marijuana, catnip (for cats obviousley), as a medicine, or that only kill certain animals: theobromine for example. For what reason do plants have chemicals in them that seem to serve no other purpose? (cite will be forthcoming - I think I remember something about aspirin being a derivative from willow bark)