User blog comment:JohnnyN64/Mysteries of Fairy Tail/@comment-6152051-20140611062120/@comment-25009609-20140612031638

Here is my theory about the Celestial Spirits.

They were first born as humans. The one who turned them into celestial spirits was Zeref himself. I guess their memories when they are still human also disappeared just like what happened to Acnologia.

I believe that the reason for Zeref to do that thing will yet be explained before the series ends.