In 1976, evolutionary biologist Richard Dawkins proposed an analogy between cultural and genetic evolution in his influential book The Selfish Gene by suggesting the existence of a new kind of replicator on the planet, a unit of cultural transmission which he called the “meme”. Memes are responsible for cultural evolution, in the same way that genes are responsible for biological evolution, except that in the case of the meme, evolution is much faster. Dawkins defined memes in the following words:
“Examples of memes are tunes, ideas, catch-phrases, clothes fashions, ways of making pots or of building arches. Just as genes propagate themselves in the gene pool by leaping from body to body via sperms or eggs, so memes propagate themselves in the meme pool by leaping from brain to brain via a process which, in the broad sense, can be called imitation.” 
As “living structures, not just metaphorically but technically”, memes parasitize brains and become vehicles for propagation. Dawkins in essence considers only this route of transmission (from brain to brain), but later it becomes clear that a meme can also be propagated independently in a book, a recording, a computer file or other medium. The author also applies the principles of natural selection to memes and considers their principal qualities to include longevity, fecundity and copying-fidelity. This last quality, however, is subject to the possibility that each transmission of a meme could create a mutation, a slight change that contributes to its evolution. Natural selection involves some competition, and even a metaphorical intent would lead a meme to seek to perpetuate and propagate itself as much as possible.
“The computers in which memes live are human brains. Time is possibly a more important limiting factor than storage space, and it is the subject of heavy competition. […] If a meme is to dominate the attention of a human brain, it must do so at the expense of ‘rival’ memes.” 
Dawkins concludes that “We are built as gene machines and cultured as meme machines”  and in fact propagates the idea of a fertile meme, which leads to popularisation of the study of cultural evolution. While memetics (defined by Elan Moritz as “a new field that deals with the quantitative analysis of cultural transfer” ) has been heavily criticised, the concept proposed by Dawkins nevertheless raises interesting thoughts about how ideas are transmitted and to what extent cultural heritage may even be more important than genetic inheritance. Among the authors who have explored memetic processes, Susan Blackmore highlights the value of imitation in the evolution of human beings, and while she warns that we should be cautious about drawing analogies between memes and genes, she states that memes have ultimately had an effect on biological evolution. According to Blackmore, “we have coevolution between replicators and their copying machinery” , which would make memes the co-architects in the evolution of the brain.
Parallel to these investigations, the meme has become a term widely used in popular culture, particularly with regard to user-generated content in Web 2.0. As a data network constantly fed by millions of people, the web is a perfect breeding ground for memes, which can replicate and spread rapidly. The viral distribution of content is a frequent phenomenon, fuelled by advertising agencies looking for new ways of gaining access to consumers and hoping that the users themselves will distribute their ads. At the same time, the desire to be part of a community and participate in a collective enterprise – even a running gag that is spread in forums, chat rooms and social networking profiles – feeds the creation of shared content. This content, which is distributed, copied and modified, offers up the memes of the internet, perhaps less momentous than those defined by Dawkins or less decisive in biological evolution than Blackmore suggests, but subject to the same rules.
The memes of Web 2.0, whether jokes featuring cats, anecdotes or YouTube videos, are, in spite of their banality, visible signs of the transmission of ideas and the dynamics of a cultural evolution in which variation, selection and inheritance are applied. Let us consider, for example, a recent viral distribution phenomenon of content on the Internet: the “Harlem Shake”.
In early February 2013 a video posted on YouTube, in which a group of Australian teenagers dance to electronic music, became an unprecedented media phenomenon. Entitled “The Harlem Shake”, the barely 30-second long video is in fact an imitation of a comedy sketch by the student George Miller, known on YouTube for his short films filled with absurd humour. In the original video, Miller and his friends groove in a somewhat ridiculous way to the song “Harlem Shake” by DJ Harry “Baauer” Rodrigues. The young Australians use the same music, but introduce a variation: in their video, first one of them dances while the others ignore him, then there is a jump cut and suddenly they are all dancing. Both videos spread quickly in a few days and the number of viewings reached five figures. At this point a third video appeared, created by Maker Studios, a company specialising in content marketing on YouTube. Maker created a clip imitating the Australians, but added a new twist: here there are employees dancing, wearing costumes and doing absurd things like punching an inflatable giraffe.
In just ten days, the Harlem Shake became a global trend. Students, soldiers, athletes, comedians, advertising agencies and all kinds of people posted thousands of videos in which they created their own version of the video by Maker Studios, with three inescapable elements: the same track by Baauer, a first segment in the video in which a person dances alone beside an indifferent group and a second segment in which the whole group dances, dresses up or does absurd things. The viral distribution of a video of this kind is nothing new. What distinguishes the Harlem Shake is the speed with which it achieved mass distribution, and then just as quickly died out.
As indicated by Kevin Ashton in an article outlining the history of this viral video, it was not the users, but companies that contributed to its success, from Baauer’s record label to the advertising agencies that took on the task of posting their own version of Harlem Shake (February 20, AdAge blog indicated that more than 60 agencies had joined this trend), and, of course, Google. The interest of advertising agencies in this mass participation (to avoid “being left behind” by the competition) and the profits gained by both Google and the record label catapulted the dissemination of Harlem Shake. However, what was also essential was the enthusiastic participation of thousands of people who not only got organised to create their own choreography, but who did so extremely quickly. As Ashton points out:
“A few years ago, few people would have posted a video of themselves singing or dancing on YouTube. Today, for many, doing so is not only second nature—it’s urgent. In our real-time culture, meme speed matters. Primacy is more important than privacy.” 
The Harlem Shake is one of those memes that, in the words of Dawkins, “achieve brilliant short-term success in spreading rapidly, but do not last long in the meme pool” . Before achieving its maximum dissemination, it underwent at least three mutations, the last of which (it is worth pointing out) was made by viral marketers. It is highly unlikely that the original video in which George Miller dances around in a pink suit would have been the subject of large-scale imitation, while the video by the young Australians is limited to the context of the home. The video by Maker Studios marks the equivalent of the biological fitness of the meme by introducing a series of parameters (the community of office workers, the contrast between the seriousness of the workplace and the party that breaks out), which encourage the action represented to be imitated and undoubtedly foster a certain kind of group catharsis.
The meme thus achieved maximum publicity, yet its excessive popularity brought its replication to a halt after only a short time. A comparison with other viral broadcast content on Google Trends over the past 12 months (see chart) reveals marked differences in the evolution of this meme. The blue line represents the popularity of the term “Gangnam Style”, referring to the track by South Korean rapper Psy: a curve that rises quickly, stays steady with a few bumps and then falls progressively. This is the usual course of a media product, supported by the communications industry and media. The yellow line shows the evolution of searches for the term “grumpy cat”, the label on a series of photos of a cat whose features have inspired a running gag. This curve is typical of a common meme in forums and chats, with small but steady popularity. Lastly, the red line marks the evolution of the popularity of the “Harlem Shake”: a steep rise and a precipitate decline. The unusual case of this viral video is thus a clear indication of how the “natural” evolution of a meme can be modified: if, as Dawkins argues, a meme needs to command the attention of the human brain by competing with other rival memes, in this case it seems that the meme has become its own rival.
This simple analysis shows that memetics can help us examine the seemingly chaotic dynamics of cultural transmission in a society in which virtually every receiver can be a sender and in which traditional mass media models have given way to a new and more complex system of relations between producers and consumers. The concept of the meme also opens a space for a new perception of evolutionary processes, which allows us to examine how the life of an idea develops.
 Richard Dawkins. The Selfish Gene. The biological basis of our behaviour. Spanish edition – Barcelona: Salvat Editores, 1993, 251.
 Richard Dawkins, op. cit. 257.
 Richard Dawkins, op. cit. 262.
 Elan Moritz, “Memetic Science: I – General Introduction”. The Institute For Memetic Research, 1990.
 Susan Blackmore, “Evolution and Memes: The human brain as a selective imitation device”, Cybernetics and Systems, Vol 32:1. Philadelphia: Taylor and Francis, 2001.
 Kevin Ashton, “You didn’t make the Harlem Shake go viral –corporations did”, Quartz, 28 March 2013
 Richard Dawkins, op. cit. 254.