http://elanguage.net/journals/sal/article/view/1402/960The Rahaweyn people and most of the Digil federation, living the lower Jubba Valley and the Baay-Bakool plateau of the Shebeelle Valley, speak Maay, while the speech of the Jiiddu and Tunni clans are classified as separate languages. Most Garre in Somalia speak Garre as a mother tongue, but Maay is the mother tongue of some. The Garre language is close to Boni. (Most Garre and Ajuuraan in Kenya speak an Oromo language named after them: Garre-Ajuuraan.) The Debarre clan of the Garre also speak their own language, more closely related to Maay. Many Somalis speak various languages as a second language. Clans are genealogically based and cut across language lines. Comparative language studies show that Maay, Tunni and Jiiddu retain older vocabulary and structure than "standard Somali" language forms.
Here's Professor Abdalla Omar Mansur (expert linguist) discussing the differences between Af Maay & Af Maxaa tiri. One being af-guri, while the other is af-guur. Probably one of the most interesting interviews about the Somali language.
http://www.bbc.co.uk/somali/war/2010/11 ... suur.shtml
If you skip over to 11.20, you'll hear where he discusses that Maay is much older than Af Maxaa tiri (standard Somali) and evidence is in how much of Maay is retained, while much of Maxaa tiri has been lost over time, then replaced with either Arabic, Harari, English or Italian. So much for Mudug, Nugaal and Northern Somali being the only "original" one.
On how much Maay & Southern dialects have retained the Somali language, while others have lost it:
On the origins of most clans & their relationship dynamics:
Some of Professor Abdalla Omar Mansur's published works include:
http://www.cfpar.org/1981 Afafka Bahda Kushitigga iyo taariikhda af-Soomaaliga (The Cushitic Languages and History of the Somali Language), 159 pp. Mogadishu.
1984 "Some traces of Somali History in Maay Dialect," in Labhan T. (ed.) The proceedings of the II International Congress of Somali Studies, vol.I, pp.271-6, Humburg: Helmut Buske Verlag.
1988a "A lexical aspect of Somali and Eastern Cushitic Languages" in Puglielli A. (Ed.)
The Proceedings of the III International Congress of Somali Studies, pp.11-18, Rome.
1988b Le lingue Cuscitiche e il Somalo, Studi Somali No.8, 130 pp., MAE, Rome.
1995a "The Nature of the Somali Clan System", in Ahmed Ali Jumale (ed.) The Invention of Somalia, The Red Sea Press, Inc. Lawrance Ville.
1995b "The Cancer of the Somali State," in Jumale Ahmed Ali (ed.) The Invention of Somalia, The Red Sea Press, Inc. Lawrance Ville.
1998 "Somali: From an Oral to Written Language in" DIOGENES in No. 184, vol. 46 / 4, pp. 91-101, Bergbahn Books, New York. Oxford.