Phonetic destiny

In Danish and its ancestral languages, medial (and final) stops have been undergoing reduction for more than a millennium: Old Norse often has voiced fricatives corresponding to stops in other Germanic languages (rauð corresponding to English red, German rot), and Danish then created more (ON hvít > hvid /við?/). And now the same thing seems to be happening in colloquial Danish: bakke /?b???/ can be pronounced as [?b??(?)] in rapid speech.

Likewise, German seems to be obsessed with hardening initial consonants. First the Germanic one, then the High German one, and now in many varieties, /ptk/ are aspirated and thus ready for another shift.

And Slavonic seems to have undergone several palatalisations, one after another.

It can thus feel like languages are destined to move in a specific directions, thus the title for the posting.

However, destiny is not a very scientific concept, so what is really going on?

One possibility is that it’s random. This cannot be dismissed out of hand, and further study is needed to determine whether phonetic destiny is statistically significant.

If it isn’t random, my best guess is that it’s caused by ways of speaking. Some languages are on average spoken faster than others, some are spoken more sloppily or with less jaw movement, and then there’s the contrast of syllable-timed vs. stress-timed languages.

My guess is that certain ways of speaking leads to certain sound changes being likely while effectively ruling out other sound changes.

For this to be the cause of phonetic destiny, it would require such ways of speaking to be much more stable than specific pronunciations, lasting centuries if not millennia.

This long time-frame makes this very hard to investigate scientifically. I guess one could try to find old perceptions of other languages. For instance, have any Norwegian or Swedish medieval sources commented on how the Danes pronounced their language?

One could also try to find unrelated languages that are known to have gone through similar sound changes recently and investigate whether their pronunciations are similar in other respects, e.g., whether they are spoken equally fast.

Does anybody know whether anybody has already investigated this topic?