One of life's mysteries

Call it nature or nurture, but all the things we do and have learned can be attributed to the intricacies of human genetics or our surroundings. For instance, we inherit diseases and certain traits from our lineage, we wipe our asses clean after taking a dump because after our parents taught us how, we're familiar with using cutlery to eat our meals, we talk and think like a gangster because we watch too much of The Sopranos, we can speak several languages because we learned it from foreign dramas, dan lain-lain.

But what really stumps me is...

WHO TAUGHT US TO DIG OUR NOSES?

Interesting isn't it. That we don't really know how we came to pick up one of life's simplest hygienic pleasures. I don't recall my parents ever sticking their fingers into their nasal cavities and telling me, "Now look here Xian, this is pnee sai. Do this and that itch in your nose will finally go away."