The earliest evidence of this dates back to the Paleoithic period, the most notable example of which being the paintings and engravings contained within the Lascaux caves. These were unwittingly discovered in 1940 by four teenagers. The images depict scenes of every day life, predominantly animals and hunting, and were incised into the cave walls with animal bones and/or painted with natural pigments. It is, however, subject to debate whether these images are in fact graffiti as it is likely they were allowed to be created by members of the society at that time.
Another primal example was found in the Ancient Roman era in Pompeii, where, in the Villa of the Mysteries or Villa dei Misteri, there is one of the earliest caricatures of a politician.
A particularly recognisable example of early graffiti is Kilroy, or Chad in the UK, a character who originated around World War I and was widely known and replicated by Americans during World War II. The doodle of a man peeking over a wall accompanied by the words "Kilroy was here" would show up on the walls of places where they were stationed, their equipment, and, later, the WWII Memorial in Washington D.C. In the UK, he would appear with the slogan "Wot, no sugar" and similar statements indicating the shortages of food and rationing.
The popularity of the expression is thought to derive from the outrageousness of the places it would turn up, and the stark contrast it would emphasise between a lighthearted cartoon and the darkness of the war and poverty of the era.
Graffiti holds the power of giving every day people a voice, and of being a means to make their opinions heard. As such it was prevalent in the huge May 1968 protest in France. The frustration felt by the protestors - most of which young people and students who longed for a more liberated moral ideal - led to civil unrest, which inspired cultural creative material, particularly in the form of posters and slogans. The internet holds exhaustive lists of these, but generally they express the anarchism, rebellion and millenarian spirit of the students involved in the protest.
The art also became popular in the 1970's in New York, particularly in the form of spray can graffiti, and ran alongside the rise of hip-hop culture. It was a way for people living in run-down and neglected areas of the city to cry out against the huge contrast between classes; between the rich and poor. The addition of signatures increased this idea of announcing a presence, and essentially was a way to say, "we will not be ignored".
This point in history was very well captured by the photographer Jon Naar.
The medium has increasingly been used as a means of commenting on society, and inspired a new art style known as Neo-expressionism, produced by artist Jean-Michel Basquiat. It rose as a reaction against minimalist and conceptual art of the 70s. Painters of the style mostly portray recognisable shapes and objects, such as the human body, but in a rough expressive way, using vivid primary colours.
In 1984, famed Pop artist Andy Warhol collaborated with Jean-Michel Basquiat to create the Neo-expressionist painting General Electric with Waiter. The company General Electric is one of America's largest corporations, yet they have been known to not pay taxes; the painting, which includes a large image of the logo, acts as an expression of resentment against this fact, and against corporations in general.
Graffiti has inspired public conceptual installations, such as Jenny Holzer's Times Sqaure Show in the 1980s, in which short statements are projected in huge text upon the side of buildings. The aphorisms, or "truisms" are statements of which we are already aware, but the sheer scale of the projections reminds us and forces us to further contemplate the truth.
The influence of graffiti in the video game and animation worlds is clearly seen. Jet Set Radio is a game for the Dreamcast released in 2000 which features a pioneering use of cel-shaded graphics. The general story of the game is set in a future Tokyo where freedom of speech has been outlawed. The player is a "rudie", a term used in the game to refer to young people who use skating and spray-painting as a form of self expression. Much of the game, therefore, is spent completing challenges which test your speed and in-game graffiti skills.
Similarly, games such as the PSN's Sideways: New York and also Grand Theft Auto feature graffiti and tagging as in-game elements.
In animation, the illusion of movement has been created by images being painted on the walls of public spaces. The anonymous Italian street artist Blu created a popular film entitled MUTO which features a lot of surreal and ambiguous imagery.
A similar effect has been replicated digitally for the purpose of advertisements, as seen in numerous adverts such as for the Vauxhall new "Corsa" (here), Credit Confidential (here) and BBC 6 Music (here). However this has caused some controversy as the origins of the style were not intended for commercial purposes, and indeed the original artist Blu probably wouldn't be pleased to know his style is being imitated by advertisement agencies.
I find it quite ironic that graffiti-inspired art has ended up becoming a significant tool for advertisements, as that's what earlier graffiti artists were fighting against: corporations and greed. However, aside from that, the videos and images themselves remain compelling and charming. Street art, also, has evolved to become something to marvel at and not treat with scorn and disapproval, and the fact that these artworks are freely available to see, and not created with the intention of making money, shows a true artist's spirit at work, and therefore I admire it greatly.