Africa is the continent on which humanity originated from, and peoples in other continents migrated in waves. So the most insular communities in Africa have had

Africa is the continent on which humanity originated from, and peoples in other continents migrated in waves. So the most insular communities in Africa have had more time to diverge than the most insular communities in other continents. They are talking with respect to internal diversity I believe. As an Anglophone you may notice a similar thing in language, and in English you can notice the large diversity in accent in native UK speakers.