Years ago when I taught linguistic-based English in 8th and 9th grades, I remember something that was so interesting that I mentioned it to Heaven Admin who also found it very interesting. I no longer have the book I used then, and I haven't found anything about this on the internet.
Here's what I remember:
Language changes. For example, hundreds of years ago, people from England who naturally spoke English came to the United States. Over the years, we now have British English and American English. The pronunciation is different, and some of the vocabulary is different. Language changes, and, over time, it also changes according to where the language is spoken.
Change in language was compared to change in sheep who were transported to other areas of the world.. After so many generations, the sheep that started out exactly the same are noticeably changed. For example, in some countries the sheep are much smaller, and in other countries larger. They are still sheep but not exactly the same as they started out.
I remember that this was called biologic or biological progression.
Does anyone know where to find out more about this? My special interest is in language.
Normand, I have a feeling you might know about this.