The theory of evolution is used to describe (or even generate) characteristics within some population based on three processes:
- Variance - there is variation of characteristic within the members of the population
- Reproduction - variation can be transmitted to offspring
- Selection - a variation will be selected, or filtered, by the environment
Consequently, the operation of these three processes can be used to describe the development of organisms and their characteristics.
For example, within a population of birds a characteristic of a single bird raising the alarm upon seeing a hawk can be described as follows: a community of birds with that characteristic will likely be more successful in a predatory environment than those without — even if it disadvantages the particular bird that does the warning! Note, that this "inclusive fitness" says nothing about the altruism or will of the bird, or even the desire of genes. While the term "selfish gene" or koan-like statements such as, "the chicken is merely a way for an egg to create more eggs," are useful as a rhetorical device to focus on the salience of the gene, it is inappropriate with respect to the theory. Once the point is made, an evolutionist warns that it is incorrect to associate genes with a desire of their own. It is merely a descriptive/generative theory for why certain organisms/characteristics emerge.
Richard Dawkins, a supporter of the theory above, was challenged as to whether he could identify any domain other than biology in which these three process operated; he responded with the theory of memes in the concluding chapter of his book The Selfish Gene. In memetics one can ask why a particular idea (a variation) is common within the population of ideas, and does it have any particular characteristics that favor its reproduction or selection within that environment? For example, one might identify chain letters within a population of postal mail. (See Chain Letters and Evolutionary Histories.) What can explain the appearance of this phenomena, what is the relationship of those characteristics to an environment such that they are reproduced or selected? A chain letter tends to be reproduced because it demands that you reproduce it; when you do reproduce it you are asked to send it to multiple recipients who do the same (a geometric growth rate); and it promises favors or threatens catastrophes. All good reasons to find that within a particular environment chain letters are common. Consequently, a theory of memes can be useful in identifying ideas, or even the boundaries of a collection of sympathetic ideas, and their characteristics that permit them to perpetuate within a cultural environment. Dawkins had proposed some interesting analytical variables for memes including copying-fidelity, fecundity (rate of reproduction), and longevity. However, these can be difficult variables to use, just as they are for genes. For example, when exactly can we say that a new species has appeared? Or when is an offshoot of a religion, no longer that religion?