This has been an ongoing debate for quite a while now, and customers frequently ask me this.  Primitivo and Zinfandel are genetically very similar.  They are both clones of the ancient Croatian grape Crljenak.  Since both clones come from the same original varietal, most of the differences we see today have come about from normal mutation.  Grape vines are very prone to mutation, and not necessarily in a bad sense.  Grapes tend to...