This has been a theory in my head for a long time but with Vegapunk I believe how devil fruits we’re created has been effectively deduced. It all has to do with ones lineage factor, first let’s go over the things we know about lineage factors.
First is that law explains to us that the lineage factor was first discovered by Vegapunk. He also lets us know that it takes the lineage factor to actually create S.A.D. This is a crucial hint, S.A.D makes smiles, and smiles are not copies of devil fruits, they function very differently from them. If the lineage factor can mimic devil fruit powers even on a basic level than its fair to assume the lineage factor is HEAVILY important to the way devil fruits work.
Next is them being described as “the blueprints of life”. Essentially one person’s lineage factor can be used to clone them, meaning tons of things about people, their builds, their strength, and many other things can be directly gained from the lineage factor.
Vegapunk explains that devil fruits are a possibility for human evolution that someone desired, this is a purposefully vague statement that if taken literally means devil fruits are magic, however 1090 gives us another, imo more likely possibility.
Here is the crux of the theory, if the lineage factor can carry intense emotions for someone through the lineage factor than it should be possible that someone’s intense desire is also carried. With that being a possibility perhaps we can actually deduce that applying the lineage factor can create the different classes of devil fruits, and heavily implies devil fruits are man made.
Paramecia: By applying someone’s intense desire to a fruit it can gain the ability to change the lineage factor granting someone the seemingly random powers of a paramecia. Someone deeply wants to be a jacket, perhaps in their lineage factor, that intense desire can be applied to make the JACKET FRUIT. Someone wants to control and produce mochi, that intense desire can be applied to make the mochi fruit, etc.
Zoan: By applying different animals lineage factors in the same way they apply the desire of humans, it’s possible that a person can become that animal, it’s also possible these are created in the same way paramecia are, due to the next category.
Mythical Zoans: Someone’s intense belief in a deity or mythical creature can create a desire to become said mythical creature, explaining how Vegapunk can easily recreate Kaido’s fruit. If both paramecia and zoans are made the same way it explains why Vegapunk can copy the two fairly easily
Logia: Logia are the trickiest and hardest part to see, while I can just say that its someone’s intense desire to become that element, Vegapunk has not recreated these fruits at all. It seems they function somewhat differently to the rest of the fruits, and probably effect more than just the lineage factor.
There are still things very unexplained but can also be explained with this theory. If someone’s lineage factor is applied to the fruit it makes sense why fruits can have minds of their own. Zoans are probably the only ones that actually can somewhat apply this, basically the personality of the animal or mythical creature is applied to the fruit.
The only thing I cannot explain is devil fruit reincarnation, you could say that someone’s will is so strong it gets reincarnated, but I can’t see that for the guy who wanted the jacket fruit. It seems like there is another reason for this functionality of devil fruits, but it could also be easily tied to the lineage factor, we’ll just have to see.
TLDR; I believe that devil fruits are entirely man made, and are various applications of people and animals lineage factor. The intense desire to want something essentially can be transferred from their lineage factor into fruits and change the lineage factor of other people.
Theory by SamCatJackson (https://www.reddit.com/user/Successful-You-1288)
