I read an interesting paper the other day by Andy Butcher from Flinders University in South Australia. The paper was about phonological systems and contrasts in Australian languages. It ended with some rather interesting speculations.
Australian phonologies are rather unusual. These languages have very few voicing contrasts, very few vowel contrasts, and very few fricatives. That is, the languages make little use of distinctions manifested below 400 Hz, and above about 4000 Hz. These languages have no vowel distinctions which depend on formant distinctions below 400 Hz, and moreover they lack distinctions in consonants which depend on low-frequency cues such as voicing, and high-frequency cues such as frication.
Butcher points out that these are precisely the frequencies which are most affected by chronic middle ear infections — that is, people with chronic middle ear infections are most likely to suffer significant hearing loss, and the frequencies between 500 Hz and about 4000 Hz are the areas most likely to be preserved.
It’s well known that middle ear infections are a very serious problem in present day aboriginal communities, but it’s not known whether this is a post-contact phenomenon caused, or whether this could have been around in aboriginal populations long enough to have shaped sound change over hundreds if not thousands of years. I had always assumed that the high incidence of ear infection was a result of poor community housing, poor access to antibiotics, and generally dusty living conditions. I talked about this with a community nurse at one point and she was under the impression that the coastal communities had a much lower incidence than the desert communities. Andy cite some evidence that it’s possibly longer term.
I think this is a really interesting idea. We know of cases of a high incidence of deafness in a community leading to signing — spoken bilingualism (such as Martha’s Vineyard) but this would be a case of a high incidence of deafness in the population leading to changes which exploited the frequencies that are most likely to remain intact, that is, the sounds which people are most likely to be able to hear.