At least that's what is taught now a days, the world government managed to take and Iron clad hold thanks to the schools they began to build around 500 years ago. They've covered up a lot about what happened during this great pirate era, most of what is taught about it is that no one was safe from random attacks. Things became more complicated once quirks began to appear around 300 years ago. For awhile the world government seemed to associate these quirks as devil fruits, a foul tasting fruit that would grants strange powers at the price of losing the ability to swim in the vast sea. Alas Reaserch conducted by these quirk users seemed t oconfirm they are indeed seperate from devil fruits. For example a quirked human will retain their ability to swim but have different side effects of their quirk that could even be harmful to themself. Heck most people now adays believe devil fruits to be merely a legend, only whispers exist of them still being out their. In any case pirates still exist even in this great peacful era, there are still men who oposse the rule of the world government, and men who simply have dreams that the refuse to compromise on to this day. Out of the worlds population only around 50% of humans will develop a quirk. Humans are not the only intelligent species either. There are the fishmen though now a days they can be pretty rare to see as they prefer to stick to the sea and avoid the world government as best they can. There are also stories of people who live in the sky, though the world government hasn't confirmed or denied the existence of these people My hero acedemia is owned by Kohei Horikoshi and One Piece is owned by Eichiro Oda.All Rights Reserved