One of the fundamental properties of our Universe is that it is crowded with bits of information. Everything is quantifiable and everything is measurable, in fact, to describe absolutely anything in the world all you need are two digits: 0 or 1. This is a mathematical approach. Another unit of information that is commonly found in nature is the gene. Genes rely on a more sophisticated alphabet - nucleotides. These are the building blocks of DNA and they exist as a one of four "letters": adenine (A), guanine (G), cytosine (C) or thymine (T). The gene-centric theory of information is what I would call a biological approach.
In one of the relatively recent theories (1976) a new unit of information has emerged. The unit "meme" is used to describe an idea, concept or a symbol that can spread from an individual to individual. It is not a coincidence that a word ‘meme’ sounds similar to ‘gene’. The term was coined by Professor Richard Dawkins and comes from a Greek word ‘mimeme’ which translates to imitation. Memes are the cultural equivalents of genes, and just as genes do, they replicate, mutate and respond to selective pressures.
A meme, unlike a gene, is not easily definable, but is fairly easy to conceptualise. If you have ever been humming to yourself and someone else has picked up that melody, you witnessed the meme transfer. Sometimes, something as simple as an icon of a bitten apple on the phone can be enough to make the majority of the world desire to have this icon on their phone as well. It has also been seen in history; a simple cross known as the swastika made millions of people turn against each other in pre-WWII Germany.
Whenever you see a certain behaviour or style becoming popular you see memes in action. If you still do not believe me, I have to ask if you have ever heard of Mozart’s "Eine kleine Nachtmusik"? If not I highly suggest that you search for it on YouTube. I believe this will demonstrate how potent an element like melody can be while the actual name will be only known to few.
But memes are not unique to humans. Although animals do not form cultures, we observe that some animals can learn certain behaviours and then teach them to other individuals. This usually applies to animals phylogenetically related to humans like apes, but some examples of meme transfer can be observed in birds as well.
Memes do not have to be solely restricted to simple systems like icons or behaviours. The term ‘memeplex’ has been coined to describe a cluster of memes that co-replicate and coevolve in a system as a whole. The largest and oldest known memeplexes form religions and doctrines. Just like genes, memes have a higher probability of being replicated (passed on) if they act together rather than individually. This is very similar to the operons found in bacteria. An operon is a cluster of genes that is coordinated by a single control unit (promoter). Usually genes from an operon have to cooperate to fulfil a certain function. Therefore, if all genes from an operon are needed, they have a higher probability of being passed on as a whole.
But genes aren’t the only biological analogy we have for memes - they’re also similar to viruses, hence the term ‘going viral’. The meme propagation in today’s culture is similar to the pattern of a spread of contagions and even some epidemiology models can be used to assess it. The only restriction is that a viral-like spread of memes has to be through the imitation. Therefore, the spread of laughter among people (or any other behaviour that you knew before), cannot be considered as a spread of a meme. Spread of hysteria in a group or suicidal behaviours on the other hand can be considered as a viral-like spread of memes, as it is a learned behaviour.
The largest criticism regarding the meme theory comes from its biggest weakness. The problem is that the unit (meme) used in that theory is not easily definable. How to give a single definition to elements as different as Beethoven's 9th Symphony, the phenomenon of racism or The Ten Commandments? Another problem, one that might even seem paradoxical, is that it is a unit without any specific size. "To be, or not to be…" is an extremely fruitful meme, yet many would probably also agree that the entire Shakespeare’s Hamlet can be a meme on its own. Lastly, until recently there was no empirical way of testing the meme theory. Nowadays a neuroimaging techniques can be applied to test certain models.
It seems that our knowledge of memes cannot be applied as a tool in many science disciplines, yet if we consider memes from the evolutionary point of view they may become exceptionally powerful mean of getting insight into the development of human culture.