Category one and two combine when considering that the "universal characteristics of language may be so because they are aspects that make it more easily acquirable."2
The evolutionary nature of language is a new category of investigation that attempts to determine what occurred in our ancestral lineage that gave rise to a form of communication that is distinct from other species. This category involves genetics, paleontology, and archaeology.
However, whereas these studies benefit from a rich fossil record, evolutionary linguistics suffers from a lack of evidence. To overcome these shortcomings, linguists often make use of studies in the four categories already discussed.
However, Kinsella's research is unique in that it will not rely on the four categories. Instead, she utilizes evidence from evolutionary studies that will shed a critical light on the theory of linguistics.
The essential argument Kinsella makes is that this research is a step in developing a more unified theory of linguistics. This is much like psycholinguistics or neurolinguistics before it, which incorporate diverse disciplines in founding new conclusions.
Kinsella frames the current discussion on language within syntactic theory. She criticizes these theories for relying on theories that are based only in linguistics and don't incorporate multi-disciplinary perspectives in their analysis.
She contends that syntactic theory needs to be critiqued not merely as a means of recording observable data. In addition, syntactic theory must also be critiqued as a theory of language that must be consistent with theories in other fields.
While she acknowledges that there are many competing syntactic theories, the research focuses on the Minimalist Program and contrasts it with theories in evolutionary biology to test its validity. It's notable that the analysis focuses the validity of the linguistic side and not the biological side.
This seems to be due to the foundational role evolutionary biology plays in the Minimalist Program. Also, there is a continued view of linguistic philosophy as a 'soft' science.
Kinsella is vague in distinguishing the exact specifications of the Minimalist Program. She writes that, "...syntactic theory tells usthat the grammatical structure of language is the mediator between signal and meaning"3 and references Chomsky as privileging the internal aspects of language over the external.
While she discusses the MP's emphasis on creativity within syntactic structures, it seems that she is ultimately positioning it as a strongly internal theory of languag