Abstract
The sound systems of the world’s languages adapt to biomechanical, aerodynamic and cognitive pressures associated with sound production and discrimination. Such pressures help to yield the greater frequency of some sound types and the reduced frequency of others. In this paper I explore such adaptation, pointing out that sound systems not only adapt to such pressures in ways that are clear from a typological perspective, but that they adapt in more subtle ways that are only now becoming apparent. Furthermore, I survey a host of recent studies suggesting that sound systems likely adapt to some pressures that vary across populations and environments. While the extent of adaptation to such variable pressures is certainly debatable, the mere existence of phonetic/phonological adaptation to pressures that differ across populations is increasingly well supported. The evidence in support of such adaptation ranges from large-scale quantitative data, to biomechanical modeling, to the speech of Freddie Mercury.