Despite everything, we pick our noses.
Jennifer Ackerman, author of Ah-Choo: The Uncommon Life of Your Common Cold said colds spread most frequently from someone's nose to their hand to some object - a pole on the bus, buttons on an ATM - to your hand to your face. Colds were much worse news in the days "before hygiene became popular," 
as George Carlin put it. Natural selection would have favoured those who didn't pick their noses.
We still do, though.
Women find guys who pick their noses immature and disgusting. Unnatural selection would have favoured those who don't pick their noses.
We still do, though.
In Ashley Montagu's book Touching: The Human Significance of Skin, he suggests that various forms 
of handling the nose throughout life, including picking it, might be related to sensory memories of breastfeeding: "In nursing at the breast the baby's nose is frequently in contact with the mother's breast, and it is quite possible that the rhinal experiences there enjoyed or un-enjoyed may have something to do with these various later manipulations of the nose."
He notes that monkeys and apes pick their noses, and often eat what they find there - a behaviour commonly seen in kids, and sometimes in adults. He remarks "The association of picking one's nose and eating in such cases suggests the possibility of some form of early conditioning, and that nose picking alone may be a form of self-gratification regressive to such an early period of experience."
We carry bacteria in our noses, which builds up and becomes irritating, but this can hardly account for how much we pick.
We touch our faces one to three times every five minutes, according to Jennifer Ackerman. To avoid doing so greatly reduces one's chances of picking up colds. But try abstaining from something you do, usually unconsciously, two hundred to six hundred times a day. Good luck.
That kind of compulsive behaviour, despite negative consequences in health and sexual success, is quite probably rooted in deep, instinctual need.
The thesis of Montagu's book is that skin stimulation in infancy greatly affects psychological and emotional health throughout life, and we in the civilized West don't get nearly enough of it. As babies we're consigned to cold, prison-
like cribs. Clothes keep the mother's and baby's bodies separate, with the main point of cutaneous contact being the mouth (and little snub-nose) and the nipple. In childhood we become attached to blankets, soft toys and pets we can handle, pick up, carry around, take to bed and rub with our faces.
We should really pet and caress and stroke our babies (and each other) more often. Until we do, we'll keep touching our faces six hundred times a day. We'll get more colds. We'll pick our noses.
