Nothing is more human and fallible than the dynastic or hereditary principle, and Islam has been racked from its birth by squabbles between princelings and pretenders, all claiming the relevant drop of original blood. If the total of those claiming descent from the founder was added up, it would probably exceed the number of holy nails and splinters that went to make up the thousand-foot cross on which, judging by the number of splinter-shaped relics, Jesus was evidently martyred.