Who cursed the Devil Fruits?

Question

One Piece is near in reaching 1000 episodes, but never in a single episode where the origin of the so called Devil Fruits is elaborated. Is there any creator of the Devil Fruits or their existence are merely phenomenal?

I remember one episode when Blackbeard killed one of his comrades just to gain the Dark-Dark fruit, he was sure that based on its appearance, it was definitely the Yami Yami no Mi because he read it in the book about the cursed fruits.

How was the book written, does it imply that the author of the book is also the one who cursed the Devil Fruits?

Answer 1

Oda mentioned in SBS vol 48, that it will be revealed in the end by someone who knows how the Devil Fruit mechanism works. Quoting from the wikia:

According to Oda, a "certain professor" will explain the complex mechanisms behind all of the Devil Fruits in the series in the near future.

And I personally think all of your other questions, like "regarding the author of the book", will be answered when that happens.

Answer 2

When Shanks is talking to Buggy about Devil Fruits (in epsiode 8), he says that he heard that they were incarnations of the Sea Devil. I may be wrong but I think they're cursed because the Sea Devil itself is cursed. And it also may be that the Sea Devil is the creator of the Devil Fruits.

Answer 3

We have seen several examples of Devil Fruits that have re-emerged after its original owner died. It is known at this point that Devil Fruits don't simply disappear when the owner dies, but rather shows up somewhere in the world.

Therefore it is not far-fetched of an idea to say that someone or more likely a group of people began categorizing the fruits anytime they came across them. Over the course of hundreds of years, it should be easy enough to compile information such as what they look like, what they do, and other useful information about the various fruits.