While the brain represents just 2% of a person’s total body weight, it accounts for 20% of the body’s energy use, Raichle’s research has found.

That means during a typical day, a person uses about 320 calories just to think.

Different mental states and tasks can subtly affect the way the brain consumes energy.

“If we were to put you in a scanner and we looked at what’s going on [in your brain] while in front of the TV or doing a crossword, your brain’s activity would change if we gave you a demanding task, and it would use more energy,” Raichle says.

Doing difficult cognitive tasks like philosophising and arranging those thoughts into logical order by writing them down is a bit like the mind doing harder aerobic exercises and burning even more calories.

Using your brain is also a proven antidote to diseases like dementia. People who sit and stare at TV screens all day tend to lose it quicker than people who keep their minds active.

This suggests that earlier peoples without any mind numbing technologies were actually better off in the long run.

Having spent time with tribal people, especially in Australia, I can see how their rich philosophical lives not only mentally enriched them but contributed to their health.

The Dreaming, or Tjukurpa, beats television soap opera ‘Days of Our Lives’ hands down.

Incidentally, they also had better diets than us. They ate unprocessed animals and plants, including meat, fish, eggs, vegetables, fruits, nuts and seeds.

There didn’t have any processed foods soaked in sugar and salt and neither did they eat large amounts of grain or dairy.

There is a trendy modern version of their diet called the paleo diet but the jury is still out about its benefits.*

Like most modern diets it is being sold as a weight loss program. Tribal people didn’t have weight problems, nor did they have problems with things like tooth decay.

Part of my job at the Aboriginal Heritage Branch in South Australia was rescuing old Aboriginal burials dug up during development work.

None of the pre-contact skeletons exhibited dental caries. The teeth of the older skeletons were worn flat from the roughage in their diets but none of them had any decay.

Maybe our grandiose civilisation, comfortable as it is, will end up doing us in if we are not careful.

What seems to have been the major threat to our ancient ancestors, apart from old age, was physical trauma.

Then again, philosophising can be dangerous too. Just ask Socrates. He was sentenced to death for allegedly corrupting the young people of Athens with his thoughts.

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* The respected Mayo Clinic in the USA says of the paleo diet: “A paleo diet may help you lose weight or maintain your weight. It may also have other beneficial health effects. However, there are no long-term clinical studies about the benefits and potential risks of the diet. You might be able to achieve the same health benefits by getting enough exercise and eating a balanced, healthy diet with a lot of fruits and vegetables.”