Your mother may not approve, but there is a way to clear your nose without sticking anything inside it.
It’s called the snot rocket.
Just push against the side of one nostril to close it off, take a deep breath, close your mouth and exhale as hard and sharply as you can through your other nostril.
You’ll be amazed how fast the contents shoot out. Just make sure you tilt your head away from your body to avoid peppering yourself.
Nose-clearing tactics like the snot rocket mean there is no life-or-death reason for the co-evolution of digging digits and large, inviting nostrils.
After all, nose blockage is easily managed by breathing through your mouth. In fact, a blocked nose is really only a problem if something gets lodged near your nasal bones, where it is dangerously close to your brain.
That is a region where human fingers are too podgy to be of any use. A rather thrilling story of a primatologist, some tweezers and an engorged Ugandan tick comes to mind.
Sexual selection might have favored the relationship of finger to nostril if, say, females in the Pleistocene preferred mating with males who picked their noses, or if males and females picked each other’s noses in a courtship ritual.
However, that would be taking reciprocal grooming a little far.
So we must conclude that, yes, it is mere coincidence that your fingers fit so nicely into your nostrils. I doubt the made-for-each-other argument is going to change your mum’s opinion of rhinotillexomania. I suggest you demonstrate the snot rocket instead and see what she says.
Organs commonly correspond in size and shape to other organs with which they must function.
Conspicuous examples include the male and female sexual organs of many insects and some mammals, the mouths of baby marsupials and their mothers’ nipples, and, in many animals, elongated claws or toes that have been adapted for grooming.
However, a mismatch need not mean that the organs cannot work together.
For example, the mammalian female birth channel can obviously accommodate the passage of young that are far bigger than the male sexual organ. Apertures often expand or shrink to fit the organs that they match.
Conversely, it does not follow that, because an organ fits an aperture, it is other than coincidental. There are some other places your finger would fit into that your mum would tell you firmly to leave alone, especially if you were in public.
You have five sizes of finger and two nostrils, so to get some sort of fit does not demand much of a coincidence. Nor is there any obvious reason why there should be any selective pressure to adapt nostrils to finger-reaming.
More likely, nature intended us to dribble snot just as elephant seals do. The fine art of nose-picking is just another adventitious one in the eye for intelligent design.
We’d also like to add a word of warning that this method isn’t particularly hygienic, and could spread any number of diseases. Snot rockets should really only be practised when you are by yourself.
An expertly executed unilateral snot-rocket is indeed a thing of beauty and wonder, but we would caution against Holly Dunsworth’s suggestion that you “exhale as hard and sharply as you can” from one nostril.
Developing expertise in this technique as a schoolboy is often brought to an abrupt halt by a burst sinus and severe nosebleed.