Why did the human body develop the ability to engage with cannabinoids? I’ve heard people postulating that we’re practically build to get high, as a justification for cannabis usage, but I can’t really believe it would be the main cause for this specific natural selection. I mean; from a darwinian perspective it doesn’t really make sense – how would getting high be survival of the fittest? Also, there exist other cannabinoids than THC, so what is the effect of these, and how present are they in our daily lives and what are the effect of these?
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There’s no natural selection involved. It’s just a coincidence that the shape of cannibinoids mimics the shape of certain neurotransmitters in our brain. There are many compounds in nature like that. For instance, aspirin originally came from the bark of the willow tree. It’s not like we evolved to eat tree bark when we had a headache.
There’s some artificial selection going on, though. Cannabis has been cultivated for more than a thousand years. The original versions probably just had mild pain-killing or calming properties. The modern strains are super potent because we bred them to be that way.
>Why did the human body develop the ability to engage with cannabinoids
This is a common, but totally backwards misunderstanding of how evolution works. Evolution isn’t directed. It doesn’t have goals or a purpose. Traits emerge at random, and positive *or neutral* ones stick around while negative ones get selected out.
There’s no evolutionary link between our endogenous cannabinoid receptors and cannabinoids found in plants like cannabis. Endogenous cannabinoids are just a class of chemicals in our bodies that aren’t fully understood but help regulate a variety of our bodily processes. It’s just a coincidence that the cannabinoids found in cannabis plants fit into the receptors for our endogenous cannabinoid receptors.
They’re receptors for chemicals your body makes at happy times, like laughter or orgasm.
But when your body makes the chemicals (called endocannabinoids, no way to age that word down), they break down in the body really quickly, so for a long time scientists didn’t even know they existed, and still have a hard time studying them.
A common practice in pharmacology is to name receptors after a chemical that can bind to them in an experimental setting. Muscarinic receptors bind to muscarine, nicotonic receptors bind to nictotine etc. Accordingly, the so called cannabinoid receptors are so named for what they were found to bind to experimentally.
Like all other receptors, they are acted upon by endogenous chemicals or neurotransmitters, (the main one is called anandamide off the top my head, will need to refresh my memory) to bring about a huge variety of effects throughout the body..
Cannaboid receptors aren’t specifically for cannabis. Read about the endocannabinoid system. The receptors are actually neurotransmitters that just so happens to interact with cannabis.
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You have natural selection backwards here. There was already an endocannabinoid system in our bodies, and the cannabis plant just happened to make these chemicals that interact with the system already in place. Once we discovered that, artificial selection has occurred to the cannabis species to select for production of those chemicals. The plant world has tons of different chemicals, some of which are good for us, some are heavily toxic, most are neutral or unknown. The original purpose of the endocannabinoid system was internal regulation of hunger, sleep and pain, as near as we can tell, which makes sense, as that’s what cannabis mostly affects when ingested. More of an ELI10, sorry.
In terms of evolving along selection pressures, it actually runs in the opposite direction. Most plants that have funky chemicals in them that don’t really do much for the plant in its internal life processes, evolved to produce those chemicals as a form of defence. Plants can’t really run away or physically fight back, so they have to use static defences, if at all.
Tobacco evolved to produce nicotine in its tissues to poison insects that want to eat it. Capsaicin-bearing plants (hot chilies, etc.) evolved those substances to ensure that only birds, which aren’t affected by the “heat”, would eat their fruit and spread their seeds. Mammals just grind them up and destroy them. Cannabis likely evolved the cannabinoid compounds because of a similar effect.
We big-brained humans, on the other hand, with our large bodies and the ability to eat almost anything, encountered these substances and liked the effects. So, we keep doing it, regardless of whether it was in the plants’ interests or not. Just happenstance that some plants defences were something we liked the effect of.
Endocannabinoids are signalers for neural activity. When one neuron sends a signal to another, the targeted neuron spits out endocannabinoids in response. Cannabinoid receptors are inhibitory, and the endocannabinoid molecules aren’t bound only to synapse and can float around.
This has two purposes. The first, called *retrograde signalling*, is to tell the sender neuron “message recieved”. The second, called *neural sharpening*, is to tell all the other neurons nearby, which may also be “listening in” on the communication, to “shut up” so the one actually getting communicated to can do its job.
Every single neuron uses this system, though some areas of the brain make greater use of it than others (hippocampus and cerebellum in particular.) The cells populating these areas have more cannabinoid receptors on their cell membranes, and so are more sensitive to their effects. Consequently, they are the regions most strongly affected by THC.
Human cells, neurons, receptors, etc. can be considered like a “puzzle piece” or a “lock”.
Chemical compounds can be considered like another “puzzle piece” or a “key”.
If you make one random lock and one random key, the odds are very low that the key will match the lock.
If you make *very many* random locks and *very many* random keys, you’ll probably eventually find some keys that happen to match some locks.
Some of those random matches are then selected for (evolutionary pressure), but not all of them; some of them just happen to exist because of chance and the very large numbers involved (consider how many plants there are, and how many compounds they all make; it would be surprising if *nothing* in the plant ecosystem happened to interact with our biology, even without any evolutionary pressure at all.)
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