in the 15th century, spanish had developed a large number of sibilant phonemes: seven by some accounts, eight by others (depending on whether and are considered contrasting)—in either case, more than any present-day variety of the language. during the 16th and early 17th centuries these phonemes merged differently as they evolved into those of the different modern dialects. there were four pairs of voiceless versus voiced sibilants: dental/alveolar affricates vs. (spelled or vs. ); dental/alveolar fricatives (spelled when intervocalic, otherwise) vs. (intervocalic only, spelled ); postalveolar affricates (spelled vs. ; and postalveolar fricatives (spelled ) vs. . both and were spelled before or), and elsewhere. it is likely that deaffricated and merged with before the year 1500. the main difference between the prestige dialect of north central spain and dialects to the south (such as andalusian spanish) was that, in the north, the dental/alveolar continuants were more retracted than the affricates (the former pair can be represented as and and the latter as and ), keeping their phonemic distinction, while in the south they were homorganic. the first step away from that system was the deaffrication of in the first quarter of the 16th century. because of a differing place of articulation, this still contrasted with in the prestige dialect of north central spain, though it was a complete merger for southern dialects.