Few copying processes are accurate enough to rule out the possibility of error. This chapter addresses the questions how and why cultural information varies as it spreads, and whether there are any limitations on the changes that can occur. In particular, it focuses on two of the possible causes of variation – mutation and recombination – and on the vexed issue of memetic alleles.

Innovation and Genes

For genes, variation occurs in two ways: mutation and recombination. Mutations are sudden changes in organisms' characteristics, resulting typically from alterations in the structure of genes or chromosomes, which have the potential to be passed on to offspring. Recombination occurs when genetic material of different origins is mixed together: you have two alleles of each gene, and your offspring will receive only one of them, together with one from their other parent; they may therefore exhibit traits not seen in either of you (e.g., two brown-eyed parents might produce a blue-eyed child).

Nevertheless, there are limits on the innovation that genes can produce by either method. Why is this? There are obvious limitations on possible recombinations, in that alleles have to correspond and the possible recombinations are, though rich, finite with respect to any given gene pool. Popularly, however, genetic mutation is referred to as “random”, with the unspoken implication that just about anything is possible. In fact, unless used with care, this term may easily lead to confusion.