As far as I've been able to ascertain, the original Scots came from Ireland and wore the leine, an ankle length pleated shirt, pulled up and belted at the waist.
This would have to figure in the original design of the kilt, as well as climatic conditions and availability of material.
Neighbouring cultures, such as the Norwegians, also wore skirted garments, so it was a common idea.
Length of garment and number of pleats are still debated but I think Matt Newsome has it right and the 4 yards of wool would have been sufficient to fend off the cold and allow maximum movement for working and fighting.
(We have to use common sense in our detective's search of history and from what we know, we can extrapolate what would have been most likely to have occurred.)
So, you take cold temps, an abundance of sheep, and traditional pleated garments, and you get the great kilt.
I'll leave the history of the modern kilt to those who prefer debate over discovery.
-- Angelus Uggae (cache-mtc-aa11.proxy.aol.com) -- 1/27/08 13:11