This discrepancy between our body function and our modern lifestyle is the source of many problems, one of which is the stress factor.

For our ancestors stress was a necessary life-saving function; for us it is a deadly poison.

Stress as we know it is mainly caused by the release of a hormone named norandrenaline into our body. This is the hormone that is responsible for the 'fight or flight' phenomenon.

When a stressful situation occurs, the brain recognizes the immediate danger and distress and so it commands a burst of chemical energy to be distributed throughout the body.

This energy, in the form of norandrenaline, is like a rocket fuel for the body to consume to create an appropriate reaction to the stressful situation. The reaction to an immediate danger is that you either fight for dear life or run for dear life.

Let's imagine a sunny day in the vast savannas of Africa many eons ago. A bunch of our hairy ancestors, the hunter-gatherer type, are migrating to the great woods in the east to camp for the winter. The summer was long and dry, and for the last couple of months they have survived only on roots and the very occasional animal. By now the elders and the young are frail.

Walking in a relaxed manner, they seem to be enjoying the day, yet they constantly raise their heads to sniff the air for the smell of danger or the lure of an opportunity. And, indeed, in the late afternoon a herd of gnus is spotted against the crimson horizon. The wind is blowing eastward, providing the perfect opportunity for the hunters to approach unnoticed by the beasts. A group of men leave the others and launch the chase - lean and perfectly toned, they are quiet and as swift as young antelope. Without any commotion they close the gap and embark on the well-coordinated attack.

A couple of beasts fall to the ground wounded and the hunters finish them off quickly to avoid unnecessary suffering. They have just started to gut the beasts when a roar raises the hair on their backs - a pack of lions have managed to sneak up behind them. The lions are starved and there's murder in their careful strides. They tread closer, preparing for their deadly attack.

This is an emergency and our ancestors are stressed. Their bodies are injected with a full dose of 'rocket fuel', norandrenaline. Tremendous power is bestowed upon them and their minds become sharp and clear. This is all about survival and they have a choice - to raise their sticks and fight the lions to death, or give up their precious game and run as fast as they can.

But no matter which choice they made, if they escaped or defeated the lions it was stress that saved their lives.