contoured nut?

[Scott Reed]

While looking over my bass last night, I noticed that the nut is contoured. Is this for aesthetic reasons only or does it serve some sort of purpose (like mass reduction)? Also, has Smith ever experimented with other materials, or possibly an adjustable nut?

I am rebuilding one of my old basses and toying with the idea of making my own nut (and bridge maybe). I've found very little information about the theory behind materials and mass and what affect they have on tone. Pearl, Bone, Nylon, Graphite, Brass, Steel, etc. Each manufacturer seems to have a preference but not much info on why. Any experience that any of you have would be appreciated.