How Did The Middle Finger Become Offensive?
Giving someone the middle finger is known in the United States, Europe, and other parts of the world as a nonverbal articulation of "f*** you." It's an expression of anger or a put-down, and a versatile one at that, a way to tell others that an opinion is disgusting, that they're a terrible or worthless person, and more. The insult is often referred to as "flipping the bird," a phrase which, according to Slate, became associated with the gesture in the 1960s in England, where residents had a 700-year history of expressing distaste by making bird noises or using bird as a pejorative verb.
Other countries have their own equivalents. The "okay" gesture is Brazil's version of the middle finger, as Richard Nixon once embarrassingly discovered. In Italy, Spain, and some Latin American countries, the "rock on" or "hook 'em, horns" symbol is a way to call someone's wife a whore. Crossed fingers represent female genitalia in Vietnam, used to insult. And the thumbs-up is a way to say "up your..." in some Middle Eastern nations (via How Stuff Works).
Naturally, the middle finger likely began in the same place as many other Western traditions: Ancient Greece.
The history of flipping the bird
We know that in 4th-century Athens, a philosopher named Diogenes raised his middle finger to Demosthenes, calling the orator "the great demagogue" (via BBC). In a play at about the same time, "The Cloud" by Aristophanes, a character connects the sign with the penis when he gives the finger and then gestures with his member. The finger was representative of the phallus and the knuckles were the testicles, and their presentation was meant to say that the receiver was offering people nothing but a penis, rather than a sound argument, moral guidance, noble truths, or any other positive thing.
In other words, the finger was always offensive. The Romans, who shared the Mediterranean and Adriatic seas with the Greeks, and later conquered them, copied and adopted much from their culture, and this may have included the bird. According to Vice, Emperor Caligula had subjects kiss his swaying middle finger instead of his hand, connoting oral sex. As the BBC notes, the Romans dubbed the gesture digitus impudicus, the "indecent finger." Poets like Martial featured it in their works, and the historian Tacitus recorded that its use spread to the German tribes, who displayed it in defiance of Rome's legions.
The science of flipping the bird
Remarkably, the middle finger has received some scientific study alongside the historical. A 2019 study showed that Americans no longer associate the middle finger with a penis (via Plos One). This could seem like a surprising result. Even if the visual association was lost, the modern use of the middle finger alongside or representative of "f*** you" seems to somewhat preserve the sexual connotation of the sign from over 2,000 years ago. However, this appears not to be the case, perhaps because the f-bomb itself doesn't always carry a sexual meaning.
Earlier research showed that when you raise the finger, it makes you perceive others as more hostile than they are, according to the Journal of Experimental Social Psychology. This is because our aggressive acts prime us to judge others as more aggressive, readying us to fight to survive. In the same way, more peaceful acts on our part make us perceive others in more positive lights. Finally, there appears to be a stark difference in the benefits of verbal versus nonverbal expressions of anger. Unlike using swear words, giving the finger does not reduce pain (via Psychology Today).