Thoughts on Morphology and Cultural Evolution
Biological and cultural evolution are separate factors in determining the structure of language and languages. Cultural evolution allows us to understand properties of morphological systems that are often considered to be outliers without resorting to analytical sleights of hand. The inflectional systems of Dene-Yeniseian and Afro-Asiatic languages are notable for the persistence of their complex and unusual systems of verbal inflection. Both systems can be traced back several millennia over many languages covering a large geographical area. Both exhibit the telltale marks of cultural evolution: they are complex; they are not well designed; they are conservative; and they change incrementally, based on what is there. Almost all Afro-Asiatic languages share an unusual homophony of second and third person singular prefix and two agreement patterns, one containing both prefixes and suffixes and the other exclusively suffixing, serving quite distinct functions across the family. Dene-Yenisean languages (and especially the geographically far-flung members of the Na-Dene branch) are very conservative morphologically and share a templatic pattern of verb prefixes with numerous slots, followed by a verb stem with at most one suffix position. The recently discovered relation between the Yeniseian and Na-Dene families rests largely on this shared verbal morphology. The persistence of these two peculiar systems of verbal morphology can easily be understood as normal cultural evolution and defies other forms of explanation.
