I think Erich was right about possibility. I think it is a sign post pointing to different cultures around the planet at the time and each culture is represented with a symbolic figure like we are now. Example we are represented symbolically as an Eagle while Russia is represented symbolically with a Bear. The figures represent different tribes and cultures and the lines point towards their geographic location on the globe.
I have tried to make that connection over the years, but with no real reference of what geographic cultures would have used what symbol at that time it is nearly impossible.
The fact that the Nazca lines were created over several or many centuries would align with the way I do yard work and shrubbery pruning (very slowly and over many centuries).