It is presumed that evolution wise, being tickled shows us how to defend important and vital parts of the body (like armpits, neck etc…) from a very young age, and we laugh when being tickled to encourage others to tickle us – therefore learning this kind of defense.
If you ask me, The soles of your feet. One of the toughest parts of your body, that you walk on. Whats the deal with that? Is it that important?
I have my doubts.I’ll tickle you nonetheless.