User blog comment:Godisme/A Piggy Party/@comment-5551986-20121220003541/@comment-1393830-20121220003953

Not necessarily. We know that Shinigami age at a much slower rate than Humans. We don't know when the Zanpakuto was invented. For all we know, it could have been recently (1000 years ago or so). There is nothing that says that Shinigami have always fought with Zanpakutos. We know there are other forms of Shinigami combat other than just Zanjutsu.