1.2 billion years ago you were a flatworm crawling through the mud trying to get on land. You typically got the immune system of other more highly evolved animals sprayed into your face. This other immune system that got sprayed on you contained molecular C31b attack complexes that would put your system out-of-balance, when this happens, it's emergency kill or be killed time. This is where "fight or flight" comes from inside you. Over the millions of years this dynamic walked in to be between plants and herbivores who used it to create a simbiotic relationship, you spread caffeine seeds, with energy, and I'll give you a hit of your own fight or flight emergency response.
Today, The adrenaline 'head rush' you get from caffeine is the body's internal "fight or flight" alarm mechanism that something is wrong and to "be smart now, remember what you did just now and perfect that action (Punding) to isolate the cause of the neurotransmitter problem". Priority 1 is eject/slow the intestines to mitigate the uptake of the poison (providing more energy), don't sleep, because you might die from the neurotransmitter problem, and adrenal glands should give us a jolt to get things moving and clear out the problem.
Youtube Video Vox: Colombia Coffee Shortage from Global Warming:
https://www.youtube.com/watch?v=6IN4ZcZAUbA 