Once upon a very, very long time ago, someone discovered a cave and realised it might be just a little bit safer and more comfy to live in than the great big wild and dangerous savannah outside. And, ever since they put up a "Home, Sweet Home" sign at the entrance to that cave, we have – for the most part – preferred the domesticated part of our lives to be indoors.
It seems to have been one of mankind's better ideas, especially in a British winter, but apparently too much of an indoor existence can cause unseen problems.
So much so that the latest scientific thinking is that many people should spend a week or two every year living out of doors – or camping – in order to right some of the wrongs that our modern cave-like, artificially lit, lifestyles can cause.
A week in the wilderness, with nights lit only by the glowing embers of a camp fire, may be just the thing to re-set the biological clocks of people who have trouble sleeping and getting up in time for work, according to new research.
It seems that given the chance, our bodies naturally adjust to the light-dark cycle of the rising and setting sun.
"By increasing our exposure to sunlight and reducing our exposure to electrical lighting at night, we can turn our internal clock and sleep times back and likely make it easier to awaken and be alert in the morning," says US sleep expert Dr Kenneth Wright, from the University of Colorado at Boulder.
As an experiment his team took a group out summer camping and although camp fires were allowed, all forms of artificial light – including torches – were banned.
After a week of being exposed to nothing but natural lighting, their biological clocks were re-set roughly two hours back. And even though the total amount of time they spent asleep stayed the same, the volunteers awoke at daybreak and were ready for bed when the sun went down.
The researchers discovered this was more than just habit. Tests showed changes in fluctuating melatonin levels contributed to feeling more refreshed and alert in the morning.
In our modern electrically lit conditions, melatonin only reduces to daytime levels some two hours after waking, which explains why it can be hard to rise and shine when the alarm goes off. But after exposure to natural light-dark cycles, the hormone dips during the last hour of sleep, according to the scientists writing in the journal Current Biology.
As a result, the brain is able to rouse itself earlier, and waking up is not accompanied by grogginess.
To me, this is yet more evidence of all the evolution-busting we humans go in for. We are civilised and sophisticated despite ourselves. We occupy our modern hi-tech world inside bodies and brains which, really, were designed for hunting wildebeest, while doing the odd bit of procreating, at the same time as beating off the local sabre-toothed tiger.
One of the world's top experts on human posture once told me: "When you look at your upper body you will see that most of the major muscle groups are at the front – we have big chest and stomach muscles to help us fight. When we were surviving like wild animals out on the savannah, these would have been very useful – but now the only thing we have to fight is the bank manager, and we don't do that physically.
"However the same muscle groups are constantly tightening and stressing as we go through the daily conflict of our lives, and that is why so many millions of people suffer from bad backs. Our spines, which would have had the benefit of rigorous exercise in primeval times, are pulled out of alignment by the more powerful muscles at the front of the torso."
I find all this inner-caveman stuff fascinating. There's a sort of universal denial going on that seems to assume we are not really animals at all but some kind of super-beings, entirely removed from nature.
Yet increasingly scientists are learning that we need to be in touch with that inner creature. For example, I have written in these pages before about the public forests that are being planted near cities in countries like Japan and South Korea because experts have discovered that wandering among trees can be hugely (and cheaply) beneficial to human health in many ways.
I am also always banging on about the advantages of taking long country walks, which countless research studies show are also massively good for us.
At the same time I regularly write opinion columns damning the Government for relegating the importance of nature and the environment – the idea that we can make profits that will benefit everyone by lifting planning restrictions that will, in turn, help wreck the countryside seems insanely short-sighted to me.
A few nights camping out in the sticks might well help reset levels of melatonin, but being at one with our place in nature is about for more than that. The fact is we are as much part of the natural environment as, say, an oak tree – it's when we forget it, or try to pretend we're not, that we get ourselves into trouble.
