SCIENTISTS have split the atom, put men on the moon and discovered the DNA of which we are made, but there are 10 key mysteries of human behaviour which they have failed to fully explain. The New Scientist magazine compiled a list of the everyday aspects of life which continue to confound the worlds greatest brains, including the reasons behind kissing, blushing and even picking your nose. Here are some theories on why we do those things we do and some of the problems: 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. 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. Dreaming: Sigmund Freuds 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. Superstition: unusual but reassuring habits make no evolutionary sense; however, ancient humans would have benefited from not dismissing a lions rustle in the grass as a gust of wind. Religion seems to tap into this impulse. 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. Telegraph