Pashto, why so bizarre?

From: Rick McCallister
Message: 64376
Date: 2009-07-14


After reading Comrie, I saw how bizarre Pashto looks compared to Persian. I understand they have about 3,000 or more years of separation but they are still right next to one another and Pashto is virtually surrounded by other Indo-Iranian languages. I checked Wikipedia and this is what it says about the vocabulary.
Wikipedia "Pashto": In Pashto, most of the native elements of the lexicon are related to other Eastern Iranian languages languages; those words can be easily compared to those known from Avestan, Ossetic and Pamir languages. However, a remarkably large number of words is special to Pashto.[24] Post 7th century borrowings came primarily from Arabic. Modern borrowings come from Persian[25] and Hindi-Urdu,[25], with the modern educated speech borrowing words from English,[26] French[26] and German.[26] Many words of the educated and scientific vocabulary come from the Persian Arabic tradition.[26]

So why did Pashto undergo such a radical phonological restructuring? It seems as out there as Armenian and Albanian. Is there some kind of unknown substrate underneath Pashto?