Would anyone know or theorize why a guitars fretboard markers were originally placed where they are?

I think there may be a very clever relationship between a guitars tuning, fingering forms/positions, and music theory that I can't figure out.

They seem to be related to the circle of fifths and the "CAGED" forms/positions method, but I can't quite put it all together.

"I think there may be a very clever relationship between a guitars tuning, fingering forms/positions, and music theory that I can't figure out."

Not that I can tell with markes at the usual 3rd, 5th, 7th, 9th, and 12th fret-spaces. Chording fingerings change with different tunings anyway. The same fret locations are on banjos too. One thing though in my opinion the side dots should be right at the fret location, not in between two frets. You would have to readjust to it but in the long run you would fret more accurately.
Rick

Interesting idea. From my practical point of view, though, it's much simpler. My guess is that the primary marker would be the one at the 12th fret, to indicate the octave. Then, starting with the 1st fret, every other fret would be marked. If one follows this pattern, there will naturally be a two-fret gap between frets 9 and 12 (which is probably why some builders leave off the marker on the 1st fret, which results in a two-fret gap on either end: more pleasing to the eye than the asymmetrical arrangement if the 1st fret is marked).

Just my opinion. Anyone else?