All living organisms can transmit information between generations. The property of heredity – that like begets like – depends on this transmission of information, and in turn heredity ensures that populations will evolve by natural selection. If we ever encounter, elsewhere in the galaxy, living organisms derived from an origin separate from our own, we can be confident that they too will have heredity, and a language whereby hereditary information is transmitted. The need for such a language was central to Schrödinger's argument in What is Life?: he referred to it as a ‘codescript’. We can make some guesses about the nature of the language. It will be digital, because a message encoded in continuously varying symbols rapidly decays into noise as it is transmitted from individual to individual. It must also be capable of encoding an indefinitely large number of messages. These messages must be copied, or replicated, with a high degree of accuracy. Finally, the messages must have some ‘meaning’, in the sense of influencing their own chances of survival and replication: otherwise, natural selection will not operate.

In existing organisms, there are two such languages, not one. There is the familiar genetic language based on the replication of nucleic acids, DNA and RNA, and there is the even more familiar language, confined to humans, which we are using now. The former is the basis of biological evolution, and the latter of cultural change. In this essay we discuss the origins of both.

In fact, we will not discuss the origin of nucleic acid replication, although this was a crucial step – perhaps the crucial step – in the origin of life.