Where did the devil fruit come from?
As of right now the origins of natural devil fruits are unknown. Although Oda hinted that a certain scientist (Vegapunk probably) would explain more about devil fruits in the near future.
We know that when a DF user dies that devil fruit respawns and the devil takes over a nearby fruit, I believe the devil fruits were created by human sacrifice, we also know that the humans in one piece (by VegaPunk with the help Doflamingo and Caesar) can create zoan type artificial DFs, maybe with animal sacrifice, So Vegapunk is a scientist that sacrifices animals? But if the devil fruit are made from human sacrifices, how were they original created? What if the original devil fruits came from the sacrifices from people from an acient kingdom. There's a book of all the DFs and their power, maybe the world government were experimenting on those people. I don't know a lot more than that :)
What do you think?