I begin this post with the premise (or the assumption, if you will) that many of us are attracted to drugs, and I ask the question, "Why is it so"?

The answer I wish to offer for the reader's kind consideration is based on the observation that to improve our survival - our species began to transition (it is approximated 20,000 years ago) from solutions that are evolved (that is, changes that are embedded genetically) to those that are learned (that is, changes that are embedded memetically).

Now, for concise narrative's sake, let's agree to consider a 'speciation event' as a single point in time AND that the single point in time that the species Homo sapiens came into being was 200,000 years ago. So, for over 180,000 years, we have been operating in "hunter-gatherer mode," and we did so in small, isolated communities. I am of the belief that evolution refined this mode by carefully balancing the ratios of various neurotransmitters and their corresponding receptors to correctly activate important neural pathways.

One of the tools that helped us survive as a species during this 180,000-year period is our ability to experience stress and fear. After all, when a herd of stampeding mammoths rushes in your direction – stress is a healthy thing that should spur you into action and get you to quickly climb a tree or find shelter behind a rock before the mammoth tramples you into a carpet.

Stress is the product of a hormone called cortisol and a neurotransmitter called adrenalin. As hinted earlier, cortisol is secreted when, according to evolutionary memory, we are in mortal danger. What happens then? The hormone agitates us to feel "that something must be done." Adrenaline follows soon after to change the energy regime in our bodies. It redirects energy availability – temporarily switching off the digestive, reproductive and immune systems. It channels the freed-up energy to the muscles and the brain so that we can think fast and act fast. To continue the example from above - it's best to put everything we've got into climbing a tree before the mammoth flattens us; when the crisis has been averted things can go back to normal.

But then, after 180,000 years, when we started living in permanent settlements, two things happened. First, there were no more mammoths or dangerous predators in the vicinity. Second, we suddenly started meeting a lot more people. Interacting with strangers is inherently stressful, and before it was clearly established that the state had a monopoly over the use of violence - it was justifiably stressful. In modern society, it is usually a good idea NOT to stress. It is here that we find "a bug" in the way we evolve. The triggers that invoke the stress molecules are all around us, but to act on that stress is either forbidden or inadvisable. Nevertheless, our genetics have wired us to respond in specific ways to these endogenous stress molecules. Yet to reverse the genetics, we need a selective pressure that favours "chilling" over "stressing." But what that means is that cool cats should have more children than stress-buckets (so to speak)... but there is no natural force that drives this kind of skew, so the old genetics continue to hold.

How does this relate to psychoactives? Well, psychoactives, simply put - reduce stress – They replace the unpleasant feeling of stress hormones with feelings of pleasure and joy. That's why people love drugs, or, to be more precise, why some people will always be attracted to drugs.