Don't worry, we're happy

Which raised a lot of chicken-and-egg questions. Was happiness an outcome or the basic temperament that allowed them to negotiate all the rest with ease? When surveys show married people report being happier, for example, is this because marriage leads to happiness or because happy people are more likely to get married and stay that way?

New research is leaning to temperament being a more significant factor than circumstance, explaining why happiness levels don't change much between countries or tax brackets. Wealth matters up to the point of a reasonable living standard, after which diminishing returns set in.

Which is to say, if you are hungry and you get something to eat it makes you very, very happy. If you have eaten six courses and are offered "a wafer, monsieur" you're as likely to need a bucket as a napkin.

So, if we're born with a basic predisposition to happiness, how is it that we instinctively feel that our life experience determines our happiness?

Part of the answer is in our brains. The human brain devotes large capacity to recognising people, keeping score of debts, evaluating trustworthiness and forming alliances. This is integral to human success and thus rewarded in evolutionary terms.

Reciprocity is as essential to our genetic success as self-preservation because we have mutual interest in living in big communities where we can, through specialisation, increase exponentially the resources available to all. This was as true 5,000 years ago when humans made tools and hunted as it is now in highly mechanised production. Nobody can fully prosper making their own clothes, killing their own food and defending their own territory but if we form a group and each do one thing well we can have more of everything than we need.

We can even start worrying whether we have too much.

Since reciprocity is vital to our survival, it's not surprising that humans are concerned about networks of trust and fearful of their erosion. Our brains are well designed to detect cheating; in fact, we identify it much faster and more effectively than we detect altruism or goodness. We are on the lookout for cheaters, liars and charlatans because they undermine the social survival contract we have made to co-operate with people beyond our immediate gene pool.

Anxiety is real but it isn't new. Evolutionary behaviouralists suggest we are programmed to seek the better campsite, richer hunting fields and superior tools. When scientists monitor serotonin and dopamine responses, it's clear the human brain believes the chase is in fact better than the kill. Which goes some way to explaining why the possibility of sex with a new partner is usually more exciting than the certainty of sex with an existing partner. Or why we eat beyond the point of pleasure. Or why we sometimes buy dresses that are never worn. Dissatisfaction with the status quo and a desire to improve our circumstances is wired into our neural pathways.

For all the theorising that the mouse wheel is a plot by capitalism to keep us working, it appears more likely to be a plot by our DNA to keep us living. Evolutionary biology teaches that fear is ingrained into our survival behaviours because it serves to help us assess risk and respond to threats. We survive today because thousands of our ancestors knew to run from the sabre-tooth tiger, not eat the strange berries, and get under cover at the sound of thunder.

The sensibly fearful bore our DNA through countless mortal perils and emerged to breed. Generations of reinforcing behaviour have left us intelligently scared of infection, injury, starvation, physical assault, removal from our group, freezing, burning, drowning and multiple other perils, chief among them the fear of death itself.

Anyone who has held their child at night explaining in vain there are no monsters in the shadows has seen our inner caveman at work. A small child, though carefully preserved from commercial television, junk food, pedophiles, famine, weapons of mass destruction and the lash will nonetheless wake in fright, vigilantly alert for danger.