The general pattern observed in linguistics is that accents/dialects/languages and language families have the greatest level of diversity in the area where they originated.
E.g. Austronesian is a huge language family that covers an enormous geographic area including Hawaii, the Philippines, Indonesia and even as far as Madagascar, and it contains over 1,000 distinct languages divided into 9 subfamilies - and yet all but one of those subfamilies are found exclusively in Taiwan, where proto-Austronesian first emerged roughly 5000 years ago.
E.g. Austronesian is a huge language family that covers an enormous geographic area including Hawaii, the Philippines, Indonesia and even as far as Madagascar, and it contains over 1,000 distinct languages divided into 9 subfamilies - and yet all but one of those subfamilies are found exclusively in Taiwan, where proto-Austronesian first emerged roughly 5000 years ago.