Specifically, we have evidence of beer older than we have evidence of cereal domestication. There is evidence that beer's side effects were considered important for social and religious gatherings (as they are today as well). People wanted to make more beer and so figured out how to plant it. The process to make bread is actually a lot more involved than to make beer and porridge... and porridge just doesn't make as much sense as a motivating factor for domestication when the grains ripen at the same time as many many other easier and tastier foods are also ready in the natural environment.
Arguably, the domestication of grain and invention of agriculture played a role in the rise of many civilizations.
There's no reason to think that humans 10k years ago didn't enjoy getting buzzed, just like humans today do.
An often missed point about grains is that distilling or fermenting them into beverages made for easier transportation, storage, and resilience. Yeah, you could store grains in granaries nearby, but there is a lot of volume that makes it unwieldy for ox carts or train cars. If farmers can bottle their excess grain, then there is a diversified portfolio that can smooth over crop failures or market dips.
Of course, today the tail is wagging the dog, because liquor production is demanding far more than just the excess harvest or a portion to transport. But you can see historically why its benefits were being touted to the consumer.
Caffeine in Floral Nectar Enhances a Pollinator's Memory of Reward - https://www.science.org/doi/10.1126/science.1228806
> Caffeine improves memory in humans, millions of whom find that their daily dose enhances clarity, focus, and alertness. The human relationship with caffeine is relatively recent, however, and thus its impact on our brains is likely a by-product of its true ecological role. Caffeine occurs naturally in the floral nectar of Coffea and Citrus plants. Wright et al. (p. 1202; see the Perspective by Chittka and Peng) found that caffeine presented at naturalistic levels significantly improved the ability of bees to remember and locate a learned floral scent and potentiated the responses of neurons involved in olfactory learning and memory.
PBS Eons Why Does Caffeine Exist? (5:13 for the bit on bees) - https://www.youtube.com/watch?v=PzshAqowsyI
> In experiments on bees, researchers have found that once they've had a sip of caffeine-laced nectar, it boosts their memory, makes them preferentially revisit the plants, and even helps them pollinate faster and more efficiently. So, for plants, caffeine is a multi-purpose molecule with a lot of adaptive benefits. But, for us, it has one main benefit: it gets us through Monday morning. ...
I honestly wish mind-altering drugs were more accessible sometimes, mostly because of safety. Millions are killed by adulterants in their street drugs.
Not only drugs, almost everything is bad at the wrong dosage. Case in point: water.
That said, the state of mind must be so wild that "is it poisonous in this specific/usual sense" is probably not the right thing to discuss.
I've struggled to tell the difference between doses of LSD that exceed 100µg. Maybe I just take it too frequently to make much of a difference. It's also possible that it only increases duration, but not intensity.
What’s you’re arguments it’s not a drug?
Most people who use drug as a pejorative term also wouldn't use it to describe caffeine.
That's primarily because it's most commonly diluted 90%. Spirits (or everclear) have much lower intake required.
GHB ~8x
Ethanol ~10x
Methamphetamine ~10x
DXM ~10x
Cocaine ~15x
MDMA ~16x
Codeine ~20x
Methadone ~20x
Mescaline ~24x
Flunitrazepam ~30x
Ketamine ~40x
Phenobarbital ~50x
Nitrous oxide ~150x
LSD ~1000x
Cannabis/THC ~1000x or greater
Citation: Gable RS. Comparison of acute lethal toxicity of commonly abused psychoactive substances. Addiction. 2004;99(6):686–696. doi:10.1111/j.1360-0443.2004.00744.x
Statins for example are probably 10x to 20x (quick napkin math based on an animal study I found). Tylenol is 10x and is OTC.
Personally I consider alcohol to be much safer than many other substances given the form it typically takes. Utterly irresponsible binge drinking aside, most people will suffer serious adverse effects long before they're in danger. Compare that with pills or injections where an OD can be entirely inadvertent even when observing basic common sense.
Imagine what effect alcohol has