A snippet on phoneme change

 TIL that phoneme change doesn't happen gradually like I always thought. I assumed Grimm's Law was a slow burn. When those P's became F's, I thought there was a point in time when people said... something in between a P and an F. Which now that I think about it, makes little sense. What in heck would be between a P and an F??

But no, instead, it happens quickly. A group of people start to pronounce something in a new way. That group increases in size. The previous group dwindles or maybe dies out. Think about how a portion of the English speaking population says the word "think" as "fink?" There was no point in time where people said something in between those two sounds. Will fink ever replace think? Who knows? But it just might...