Richard Dawkins noted the three conditions that must exist for evolution to occur:
variation, or the introduction of new change to existing elements;
heredity or replication, or the capacity to create copies of elements;
differential “fitness”, or the opportunity for one element to be more or less suited to the environment than another.
Dawkins emphasizes that the process of evolution naturally occurs whenever these conditions co-exist, and that evolution does not apply only to organic elements such as genes. He regards memes as also having the properties necessary for evolution, and thus sees meme evolution as not simply analogous to genetic evolution, but as a real phenomenon subject to the laws of natural selection. Dawkins noted that as various ideas pass from one generation to the next, they may either enhance or detract from the survival of the people who obtain those ideas, or influence the survival of the ideas themselves. For example, a certain culture may develop unique designs and methods of tool-making that give it a competitive advantage over another culture. Each tool-design thus acts somewhat similarly to a biological gene in that some populations have it and others do not, and the meme’s function directly affects the presence of the design in future generations. In keeping with the thesis that in evolution one can regard organisms simply as suitable “hosts” for reproducing genes, Dawkins argues that one can view people as “hosts” for replicating memes. Consequently, a successful meme may or may not need to provide any benefit to its host.
Unlike genetic evolution, memetic evolution can show both Darwinian and Lamarckian traits. Cultural memes will have the characteristic of Lamarckian inheritance when a host aspires to replicate the given meme through inference rather than by exactly copying it. Take for example the case of the transmission of a simple skill such as hammering a nail, a skill that a learner imitates from watching a demonstration without necessarily imitating every discrete movement modeled by the teacher in the demonstration, stroke for stroke. Susan Blackmore distinguishes the difference between the two modes of inheritance in the evolution of memes, characterizing the Darwinian mode as “copying the instructions” and the Lamarckian as “copying the product.”
Clusters of memes, or memeplexes (also known as meme complexes or as memecomplexes), such as cultural or political doctrines and systems, may also play a part in the acceptance of new memes. Memeplexes comprise groups of memes that replicate together and coadapt. Memes that fit within a successful memeplex may gain acceptance by “piggybacking” on the success of the memeplex. As an example, John D. Gottsch discusses the transmission, mutation and selection of religious memeplexes and the theistic memes contained. Theistic memes discussed include the “prohibition of aberrant sexual practices such as incest, adultery, homosexuality, bestiality, castration, and religious prostitution”, which may have increased vertical transmission of the parent religious memeplex. Similar memes are thereby included in the majority of religious memeplexes, and harden over time; they become an “inviolable canon” or set of dogmas, eventually finding their way into secular law. This could also be referred to as the propagation of a taboo.