Look over here, jerks, it's a history of flipping people the bird
A brief history of showing the middle finger as an insult, from ancient Greece to the modern day

As the above image shows, there is no insult quite like either being shown or showing someone the middle finger. Why, exactly, anyone cares at all about seeing a digit stuck up in the air is one of those mysteries that we all kind of just accept, but, in a noble attempt to demystify our long history of being offended by flipping the bird, a recent video from YouTube channel Weird History traces the gesture from its earliest known uses to some famous modern-day examples.
The clip begins with examples from ancient Greece, highlighting “the phallic nature” of a single raised finger sticking out from the center of a fist and mentioning an early recorded instance of it being used when the philosopher Diogenes needed a good, unsophisticated way to show disrespect to another philosopher, Demosthenes.