When we have to give a talk to a group of people, we feel anxious and experience the bodily fear responses that do not make sense now: The system is not meant to function in this safe context.

As a psychiatrist specialized in anxiety and trauma, I often tell my patients and students that to understand how fear works in us, we have to see it in the context where it evolved. Ten thousand years ago, if another human frowned at us, chances were high one of us would be dead in a couple minutes. In the tribal life of our ancestors, if other tribe members did not like you, you would be dead, or exiled and dead.

Biological evolution is very slow, but civilization, culture, society and technology evolve relatively fast. It takes around a million years for evolutionary change to happen in a species, and people have been around for about 200,000 years. Each of us, however, sees drastic changes in our lifestyle and environment over a matter of a few years.

Let’s compare the life for which this body and brain has evolved with the life we live, from my perspective as a scientist and a physician.

What we eat

We evolved in a context of scarcity, and had to walk or run for miles and scavenge to find food; we had to work for it. When we ate, we did not know when the next time would be. When we had it, we were better off eating the high-calorie food that increased our chance of survival when hungry (greasy food feels appealing). Food was not quick to digest, stomachs also had to work hard for it: meat, fruits, vegetables, seeds and nuts. None of these contained “easy” sugary calories. The body that was prone to starvation, evolved to eat it all when available, and store it, and be stingy in its use.

Research on how self-control works could help you stick with New Year’s resolutions

But now, food is just a few feet away, and we can easily consume thousands of calories in one serving. Fatty food, which required days and miles of hunting and scavenging to acquire, is now right there in the fridge or at the McDonald’s. It is like giving full fridge privileges to your Labrador. Easy calories like soda and candies provide a very large amount of energy in a very short amount of time and confuse the whole system. We end up fat and fatigued.

How we move

Our ancestors had to be active to survive in the wild. They had to walk miles a day, and were frequently involved in high intensity physical activity: moving heavy objects, climbing, fighting, chasing a prey or fleeing predators.

This body did not evolve to sit at a desk eight hours a day, and then lie on a couch for the rest of the day munching on high calorie food, looking at a small or large screen. A contemporary American may only walk a few dozen steps to the car, drive to work, ride the elevator to the office, walk a few dozen steps back to the car, get drive-thru food, then be back on the couch. Suboptimal muscles use leads to weaker joint support, and weird postures cause pain. Pain leads to reduced activity, more obesity and weaker muscles; then comes opioid epidemic, overuse of pain medications, and back surgeries for all!

How we sleep

Before TVs, halogen lamps, and video games, our sleep was regulated by diurnal change in exposure to the big lamp in the sky and environment temperature. Light and sounds got dimmed, the body and brain had time to slow down and get ready for sleep.

Choosing between devil and angel in the fight against temptation

Well now, we go 60 miles per hour with TV and music and video games and intense stimulation by the social media (switching through hundreds of subjects in a matter of minutes), and then hope for a good night sleep – that ain’t happening. Quick 60 to 0 is not how our brains are wired.

How we fear