Interesting Facts about Mestia, No. 6

All of Mestia's many roughly millennium-old stone watchtowers have either 2 or 3 "eyes" (windows) per side.  In other words, they're very regular.  Compare this to Ushguli, 44 km away, Europe's highest village, with slightly fewer towers (about 34 to Mestia's more than 40).  In Ushguli, you'll find:  a set of twinned towers, others with 2, 3 or 4 eyes per side, and one with 4 eyes on each of one pair of opposing sides and 5 eyes on the other pair (the Museum, in Chazhashi hamlet).  Astonishing variety.  My question is:  Were Mestia's towers made first - the 2-3-eye pattern quickly established - followed by later experimentation with the form in Ushguli; or was Ushguli the place of original play with the form until it was firmly decided and then implemented later in Mestia?  In other words, which community can claim the earlier set of towers?  And, by the way, what about the other main kind of watchtower found in the Caucasus, the one with a pyramidal roof, as in Khevsureti and the North Caucasus?  Are these older than the Svan types?  What a hornet's nest to stir up!