I didn't play anything prior to bass, but I don't fit neatly into the 3 choices either. When I was about 12, I had friends who played guitar and they asked me to join their band as the bass player. I didn't know what a bass player did nor did I have a bass. They chose me because I was a friend and I was the tallest. Turned out that I really liked playing bass and took to it pretty well. I never really was interested in guitar - too small and too many other people play. I did eventually pick up double bass as well, but that's about it for me musically.