Evolve

Ever think about why we do certain things?
Caroline Williams of the New Scientist published a list of ten things we do yet science cannot explain...

Here are some theories on why we do those things we do and some of the problems:

1 – Blushing: Charles Darwin struggled to explain why evolution made us turn red when we lie, which alerts others. However, some think it may help diffuse confrontation or foster intimacy by revealing weakness.

2 – Laughter: mood-improving endorphins are released when we laugh, which seems an obvious reason to do it but a 10-year study muddied the waters when it found more laughter is produced by banal comments than jokes.

3 – Kissing: the explanation for kissing is unlikely to be genetic as not all human societies do it. There are theories that it is associated with memories of breastfeeding and that ancient humans weaned their children by feeding them from their mouths, which reinforced the link between sharing saliva and pleasure.

4 – Dreaming: Sigmund Freud’s theory of dreams expressing our subconscious desires have been generally discredited and it is recognised that they help us process emotions, but the reason why we see such strange visions has not been properly explained.

5 – Superstition: unusual but reassuring habits make no evolutionary sense; however, ancient humans would have benefited from not dismissing a lion’s rustle in the grass as a gust of wind. Religion seems to tap into this impulse.

6 – Picking your nose: the unappealing but common habit of ingesting ‘nasal detritus’ offers almost no nutritional benefit, so why do a quarter of teenagers do it, on average four times a day? Some think it boosts the immune system.

7 – Adolescence: no other animal undergoes the stroppy, unpredictable teenage years. Some suggest it helps our large brain reorganise itself before adulthood or that it allows experimentation in behaviour before the responsibility of later years.

8 – Altruism: giving things away with no certain return is odd behaviour in evolutionary terms. It may help with group bonding or simply give pleasure.

9 – Art: painting, dance, sculpture and music could all be the human equivalent of a peacock’s tail in showing what a good potential mate someone is. However, it could also be a tool for spreading knowledge or sharing experience.

10 – Body hair: fine hair on the body and thick hair on the genitals is the opposite of what occurs in primates, our close animal relatives. Suggested reasons for pubic hair include a role in radiating scent, providing warmth or even protecting from chafing.

via

Each topic goes into more detail (above someone that wasn't cited sumarized the articles), for example :

Kissing - in the amorous, lip-locking sense - is not practised in all cultures, so the urge to pucker up cannot be in our genes. Still, you have to wonder why so many of us do it and why it feels so darn good. There is no shortage of speculation.

One idea is that our first experience of comfort, security and love comes from the mouth sensations associated with breastfeeding. Added to this, our ancestors probably weaned their babies by mouth-to-mouth feeding of chewed food, as chimpanzees and some mothers do today, reinforcing the connection between sharing spit and pleasure.

Another idea is that kissing has its origins in foraging. The story goes that our ancestors were first attracted to ripe, red fruit, then co-opted this attraction for sexual purposes, developing pronounced red colouration on the genitals and lips. "Instead of reinventing the wheel you use the same template for other kinds of attraction," says V. S. Ramachandran at the University of California, San Diego. Since red lips are most obvious in Caucasians, he suggests kissing may have started at northern latitudes and then spread culturally around the world. Without solid evidence, however, even Ramachandran is wary of his own idea, acknowledging that kissing may have arisen independently several times throughout human history.

When it comes to the physiology of kissing we are on slightly firmer ground. Our lips are among the most sensitive parts of our bodies, packed with sensory neurons linked to the brain's pleasure centres. Kissing has been shown to reduce levels of the stress hormone cortisol and increase the bonding hormone, oxytocin.

There may even be a link between kissing and the way we assess our biological compatibility with potential partners. In recent years it has become apparent that we are most attracted to the smell of sweat from people whose immune system is most dissimilar from our own - with whom we are likely to produce the healthiest children. And of course kissing lets us get up close and personal enough to sniff that out.