Caffeine is an insecticide that effectively paralyzes or kills bugs chomping on the tree. Whether or not the insects go out experiencing the greatest caffeine high ever is not known. While caffeine is /technically/ lethal, it's adapted for 1g bugs, not monkeys 100,000 times more massive. So you'd really have to try to win this Darwin Award. But, if you must: to calculate the dose of caffeine you'll need to ingest to have a 50% of death, take your mass in kilograms and multiply it by 150mg. Or in terms of coffee, for every kilogram of mass you have you need to drink one latte to get a visit from the grim reaper. That's a lot of coffee so it's not surprising that there are no recorded deaths in healthy adults from this method and it's doubtful that it's even possible. Because, while you're busy getting the coffee in, your body is busy getting it out by one way or another. The rare recorded deaths from caffeine are from diet pills, pep pills and crazy people who eat the drug in its pure form. Poison though caffeine is, you do still develop addiction to the stuff. And it's is a real physiological addiction not a wimpy psychological addition like people claim for videos games and the internet. But caffeine isn't heroine -- rapid withdrawal won't kill you -- it might make you cranky and give you a wicked headache -- but since caffeine releases dopamine to make you happy and it gets rid of headaches there's really no reason to ever stop using it. And who would want to give up the stuff anyway? I mean, aside from converts to Mormonism and Rastafarianism. Caffeine is the world's most used psychoactive drug -- and with good reason it's pure awesome. It increases concentration, decreases fatigue and gives you better memory. This isn't just a placebo -- these are real effects replicable in a laboratory. And, contrary to popular belief, drinking coffee isn't a Faustian bargain where the devil gives you the ability to work faster but in exchange makes your life shorter. For normal, healthy humans there are no medical concerns. Coffee and the caffeine within it may even has medical benefits such as protection from cardiovascular disease, diabetes and Parkinson's Caffeine can even get rid of migraines, but the amount required and the and method of ingestion is uncomfortable. Moving right along you know what else you can thank caffeine for? A little thing called the enlightenment. In the 1600s people drank more beer and gin than water. But with the introduction of coffee and tea, people switched from a depressant to a stimulant. It's not surprising then that this time was an intellectual boon compared to earlier centuries. Ben Franklin and Edward Lloyd loved their coffee for the same reason that modern workers and students do. It's invaluable for staying awake and concentrating when you need to finish a TPS report or to get through that boring physics class. Coffee is the fuel of the modern world, so go grab a cup guilt-free and get working smarter and faster.