We present evidence that the geographic context in which a language is spoken may directly impact its phonological form.
I've heard this claim before actually, and I'm very skeptical about it. There was a talk at the Portland, Oregon (Jan. 2012) LSA conference a few years ago. Not sure if it's related to this particular research.
The idea was that environment changes acoustics enough to eventually result in these relationships.
Again, I'm skeptical.
In this case, a much simpler explanation is that languages in higher elevation tend to be more isolated and therefore less susceptible to outside influence. And that's how ejectives are preserved, because they're relatively rare sounds. Note that plenty of languages (for example, in western North America) do have ejectives at lower elevations (even sea level) so there is probably some other explanation.
As is said too often (but perhaps not often enough?) correlation does not imply causation.
Certainly interesting, though.
