Part of the challenge of language is coming up with some way to distinguish thousands or tens of thousands of words from one another. It would be hard to come up with that many unique sounds. What human languages do instead is to come up with phonemes and rules for stringing phonemes together into syllables, and then create words by arbitrarily pairing up one syllable, or a few, with a meaning. Phonemes are the individual sounds of a language, roughly comparable to individual letters. There are about forty phonemes in most dialects of English. (English spelling does a pretty sloppy job of matching up phonemes and letters. Finnish comes close to one phoneme per letter.)
Often in evolution organisms don’t solve new problems from scratch, but instead harness preexisting adaptations. I argued earlier that the abstract “space” of possession (“The Crampden estate went to Reginald.”) may have developed by harnessing preexisting concepts of physical space. And our abilities to recognize speech sounds may harness our preexisting capacities for recognizing the sounds of solid objects interacting. At least that’s the argument of a recent book by Mark Changizi, Harnessed: How Language and Music Mimicked Nature and Transformed Ape to Man.
Changizi notes that even though we’re mostly not aware of it, we’re very good at using our hearing to keep track of what’s going on in our physical surroundings. For example, people easily recognize the difference between someone going upstairs and someone going downstairs, and we’re pretty good at recognizing individuals by their treads. The sounds that solid objects make can be broadly categorized as hits, slides, and rings. Hits: one object collides with another and sends out a sharp burst of sound. Slides: an object scrapes against another and sends out a more extended sound. Rings: an object reverberates after a collision. Changizi argues that these correspond to the major categories of phonemes.
- Hits = plosives, like p b t g k
- Slides = fricatives, like s sh th f v z
- Rings = sonorants, including sonorant consonants, like l r y w m n, and vowels
These are not the only sounds we can make with our mouths. We can do barks and pops and farts and so on. But our auditory systems are especially cued into solid object physics, so when we try to come up with easy-to-distinguish phonemes, that’s what we focus on. And a lot of rules about how phonemes hook up also follow from this principle – for example hits followed by rings are more common than the reverse.
There’s surely more going on with speech sounds than Changizi allows for. But if imitating nature is not the whole story of phonemes, it may at least be where they got started.
Later on when we talk about writing systems, we’ll see there’s a similar argument about how these are tuned to tickle our primate visual systems.