10 MYSTERIES

The top 10 mysteries scientists STILL can't explain


Magical moment: Kissing excited the pleasure centre of the brain
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Fiona Macrae and Claire Bates


They have put a man on the moon and unlocked the secrets of the human genome.

But when it comes to the basics of human behaviour, scientists still don't have a clue.

Kissing, blushing and laughing are among the traits that have defied explanation by

biologists, physiologists, psychologists or evolutionary theorists.


Some hold that a kiss brings with it pleasurable memories of breastfeeding, and the love, comfort and security that went with it.

A less savoury suggestion is that we lock lips because we equate sharing saliva with pleasure.

Blushing also has the world's best brains flummoxed. Do we do it to appease, to seduce or to advertise our trustworthiness?

And why do we laugh at things that are not that funny? Scientists don't know.

Some of our most noble and fantastic activities - dreaming, altruism, art and superstition - feature in New Scientist's top ten unanswered questions about humanity.

More mundane mysteries also made it on to the list, including body hair and nose-picking.

Teenagers, inevitably, also pose a conundrum, with no other species going through an adolescent phase.

The transitional years may have evolved to give the brain the breathing space it needs to reorganise itself to deal with the demands of adulthood.

Or perhaps their purpose is to allow tomorrow's adults to find their feet.

Boys can learn how to be a real man before their bodies mature into that of a strong and potentially dangerous adult male. Girls, who go through puberty earlier, get the chance to practise acting like a grown-up woman.

Even nose-picking scrapes on to the list. Scientists charged with pinning down the motivation behind the habit, have so far concluded only that 'there isn't any significant nutritional content in nasal mucus'.

An editorial in New Scientist accompanying the list ponders on the strangeness of humanity, remarking: 'There is nothing more fascinating to most of us than ourselves.

'So it is hardly surprising that we have expended large amounts of effort trying to get to the bottom of what it means to be human.

'What is surprising is that there are still so many traits that remain enigmatic.

'These range from the sublime, such as art, dreaming and altruism, to the ridiculous - think pubic hair, blushing and nose-picking.'

But it goes on to say that in many cases, unlocking their mysteries can bring us closer to the heart of what it means to be human.

'They may seem quirky but the best explanations for them often have profound implications,' the piece concludes.

With that in mind, here are some scientists' educated guesses at how to explain the ten human habits that still mystify them:


KISSING

Not all cultures kiss, so the urge cannot be in our genes. Our lips are certainly one of the most sensitive parts of our bodies, with plenty of sensory neurons linked to the brain's pleasure centres.


Some believe it floods the brain with the love, security and comfort chemicals associated with breastfeeding. And our ancestors probably weaned their babies by mouth-to-mouth sharing of food, reinforcing the connection between sharing spit and pleasure.

Another idea is our foraging ancestors were attracted to red ripe fruit and so developed red lips to tempt sexual partners.

Kissing has been shown to reduce levels of the stress hormone cortisol and increase the bonding hormone oxytocin, so is good for our health and happiness.


BLUSHING

The explanation for blushing - a uniquely human trait - eluded even Charles Darwin who called it 'the most peculiar and the most human of all expressions.'

We may have originally used it to diffuse aggressive approaches by more dominant individuals. Over time it became associated with higher emotions such as guilt and embarrassment.


Neuroscientist's have noted that women blush more than men and therefore women may use it to demonstrate their honesty to men and foster trust.


'Blushing it tell you that I can't cuckold you,' V.S Ramachandran from the University of California said.

'If you ask me about infidelity I can't lie - my blush gives me away.'


SUPERSTITION

Most of us act according to certain superstitions, even though logic tells us there is nothing inherently lucky or unlucky about a black cat such as the one pictured above.
According to scientists our brains are designed to see patterns and infer cause and effect, which leaves us open to irrational beliefs.


But tending to fear the worst would have given our ancestors a survival technique and ensured they did not dismiss a lion's approach as a rustle in the grass.


Others say we have an in-built tendency to believe in the supernatural, something that religion has tapped into. Robin Dunbar from the University College of London believes religion's main function is to persuade a community to toe the line and promote cohesion.

Superstition also tends to increase in difficult circumstances, when people feel they are losing control over their lives. A study of people living in high-risk areas of the Middle East found they were more likely to carry lucky charms than other people.


ALTRUISM

Biologists believe that doing good deeds is part of human nature. They just can't decide why we do them.

After all, what is the point of helping others, if they are not guaranteed to return the favour? Robert Trivers of Rutgers University in New Jersey argues that natural selection favoured our altruistic ancestors because they could expect to benefit. However these tendencies became misguided as we developed a globalised world.


Others say altruism may help with group bonding - or perhaps we just like the buzz of doing a good turn.



ART

Art may be like the peacock's tail - an outward display that someone is a good catch.


For instance, a study by Geoffrey Miller at the University of New Mexico shows that women prefer creativity over wealth when their fertility is at its peak.


Others believe the drive to seek out aesthetic experiences evolved to encourage us to learn about different aspects of the world - those that our brain's have not equipped us to deal with at birth.

Ellen Dissanayake from the University of Washington said making an object or event 'special' would bond a social group together. It may have started as a ritual and then become more aesthetic.


TEENAGERS

As no other animal species has to suffer adolescence, it may have evolved to give the exceptionally large human brain time to reorganise itself to deal with the demands of adulthood.

'The brain is roughly the same size at 20 as it is at 12, yet we can do so much more with it,' David Brainbridge from the University of Cambridge said.

He concluded our teenage years 'are the most important part of human life.'


The period may allow tomorrow's men and women to test out their behaviour, safe in the knowledge they have plenty of time to right any mistakes and increase their chances of reproducing.


DREAMING

Dreams help us process and consolidate emotions without the rush of stress hormones that would accompany the real experience.

They also help with memory and problem-solving. People are better at recalling lists of related words and links between them after a night's sleep than after the same time spent awake in the day.


It was recently discovered that we can dream even outside of REM sleep. REM dreams were found to involve long stories with more emotion, while non REM dreams often involved friendly interactions. Patrick McNamara of Boston University believes REM dreams help us to cope with aggression, while non REM dreams support cooperative behaviour.


Now that most researchers reject Sigmund Freud's belief that dreams express our unconscious desires, the meaning of our visions in our sleep remains a mystery.

LAUGHTER


The Prince of Wales and the Duchess of Cornwall share a joke...
but scientists don't know what makes us laugh
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Laughter boosts levels of feel-good endorphins, helping us bond with others. 'Laughing at' can be used to push people away.

But what makes us laugh is more tricky - a ten-year study found that most of us are more tickled by banal comments such as 'Do you have a rubber band?' than by supposedly funny jokes.

Apes maintain the ancestral 'pant-pant' laugh when they are tickled. In humans this developed into a 'ha-ha.' It can vary between natural laughter and aggressive, embarrassed or nervous laughter.

BODY HAIR

Humans are 'naked apes' but have thick hair around the genitals, while other primates have finer hair.


It may be that the hair may waft odours that signal sexual maturity and may also act as a visual signal of adulthood.


This situation is thought to have evolved 3.3million years ago - at the same time as lice.


PICKING YOUR NOSE

One in four teenagers engage in the habit, at an average of four times a day, a study found.

Scientists say the habit brings with it no nutritional benefits - although ingesting 'nasal detritus' might help build a healthy immune response. It may also decrease one's susceptibility to allergies.

The most recent research dates back to 1966 when Sidney Tarachow from State University of New York found people who ate bogeys found them 'tasty.'