Evolution is normally seen as a time sequence based on fossil records over millions of years. Unfortunately brain capabilities such as language do not petrify or fossilize very well, so that we cannot find that kind of record.
An alternative approach is through an examination of presently existing species to piece together a possible time sequence. Unfortunately there are no easily identifiable capabilities that clearly indicate pre or proto language functions.
A third approach is to look for DNA structures that clearly indicate language capabilities and functions. Unfortunately no such structures have been identified as yet.
We suggest a fourth approach that sees vertebrates as information processors with legs. We conjecture about the information processing that must support the activities that we know about. Unfortunately, we find it difficult to understand the organic 'hardware' that we find in today's species, and we are unable to obtain a blueprint of the information processing architecture from the fossil and DNA information that we can find. In consequence a bottom up approach is blocked. We therefore focus on a top down approach that examines high level requirements for information flow and transformation without worrying about the specifics of how the information might be processed and transmitted.
There is some evidence that a transformational grammar (N. Chomsky) is universal in human languages. This gives support to the concept that there is a basic capability for spoken language that is part of the species rather than being a local cultural and historical artifact.
The traditional approach to theories about language comprehension is based on the assumption that language is for communication between individuals. It also assumes that there is a common grammar and a shared semantic reality among members of a language community, as demonstrated by professional qualifying exams. There is some evidence that there is no genetic barrier to comprehension, i.e. that an infant from a group or tribe with limited language utilization can be immersed in a different culture and become fully functional at the highest levels of language proficiency.
Computational (formal) models have focused on simulating language behaviour in humans, primarily simulating questions and answers (description rather than instruction, persuasion, or entertainment). Despite over 40 years of research, this approach has stalled.
Research on language in other species has started with the same assumption that language is for communication between individuals of the same species. There has been only minimal progress in showing how language capabilities might have evolved similarly to locomotion capabilities or sight capabilities.
We propose a very different approach. We hypothesize that there is both an inner language and an outer language. The inner language is for communication and information within an individual, such as for controlling locomotion and integrating perception with action. The outer language is for information exchange between individuals of the same species. We hypothesize that the development of the inner language precedes and underlies the outer language.