Convergent evolution is well known in the biological sciences. Similar structures emerge independently in organisms that are not closely related, because the organisms in question are subjected to similar environmental or selectional pressures. For example, horns and armour have emerged amongst the mammals and reptiles; powered flight has emerged within the insects, bats, and at least twice within the reptiles (as flying pterosaurs and as birds); camera lens eyes have emerged within vertebrates, cephalopods, gastropods, certain annelid worms, jumping spiders, and cubozoan jellyfish. You can read more here about convergent evolution in biology. Evolutionary convergence has seldom been appealed to in linguistics. Apart from this paper published in Language, another recent paper to do so is this one by Dingemanse, Torreira and Enfield published in PLOS1.
Convergent Kin-based Grammar
One type of kinship inflection that is widespread among Australian languages are the “dyadic” or “kin-group” affixes. When the Kaytetye dyadic suffix -nhenge attaches to a kinterm, it indicates that two people are in the type of relationship specified by the kinterm. Thus, alkere-nhenge (elder brother-DYAD) indicates a pair of brothers, whereas arwaye-nhenge (father-DYAD) indicates a father-and-son pair (Koch 1982: 69).
A number of languages have systems of kin-inflected pronouns. The language Dalabon has two series of “dual” pronoun prefixes. Verbs that cross-reference pairs of people should inflect according to whether the persons involved are in “harmonic” generation sets (i.e., they are either in the same generation at each other, e.g., siblings, or they are separated by two generations, e.g., a grandparent and grandchild), or “disharmonic” generation sets (e.g., a parent and child). For pairs in a harmonic relationship, such as a pair of siblings, prefixes are chosen from the harmonic set, as with yarrah- in example 1. Reference to disharmonic pairs is done with a prefix from the disharmonic set, as with ngeh– in example 2, which cross-references a father-and-son pair.
Dalabon Dual Pronoun Prefixes (Alpher 1982:20)
Dalabon (Alpher 1982:19)
|‘My younger brother and I go’|
Dalabon (Alpher 1982:19)
|‘My father and I go’|
Murrinh-Patha free pronouns and verbs inflect for gender, number and “siblinghood”. For example, the subject of the verb in (3) is two male non-brothers. In (4) the subject is two non-siblings at least of whom is female. The subject of the verb in (5) is a pair of siblings (perhaps brothers, perhaps sisters, perhaps a brother and sister).
|“The two male non-brothers (♂♂) were following.”|
|“The two non-siblings at least one of whom was female (♀♀or ♀♂) were following.”|
|“The two siblings (♂♂, ♀♀ or ♀♂) were following.”|
The above kin-inflected phenomena, along with trirelational kinterms (words that indicate the relationships between three individuals) and kinship verbs (such as the Iwaidja verb inyimagan ‘he is husband to her’) are to be found in a number of Australian languages. Although there is evidence that some forms are related, many of these structures appear to independent innovations. This map reveals the distribution of Australian languages in which these structures have been attested.
Many of these structures have developed independently. The forms are convergent because they are subject to roughly equivalent selectional pressures. These pressures take the form of conversational preferences applying to person reference items in conversation.
Joe Blythe is a research fellow at the School of Language Studies, University of Melbourne, Australia and an affiliate of the Language and Cognition Department at the Max Planck Institute for Psycholinguistics, Nijmegen in the Netherlands. The research was funded by the Australian Research Council (DP110100961 and DE130100399) and the European Research Council (240853).