One for All
You didn’t think I would forget about this one, did you? One for All is a unique quirk that the protagonist of My Hero Academia gains after a fashion. (Hey, I keep spoilers to a minimum when I can.) This is different from the other characters, who are born with their quirks, but this begs the question of just what are quirks and how are they passed on.
It is heavily implied that quirks are genetic traits that are passed down from parent to child, after first appearing in the world seven or so generations or go. I can safely use seven generations because the main villain first appeared during the time when quirks first appeared in the world, and helped to create One for All. Since that time One for All has been passed to seven different individuals, with Midoriya being the eighth when he is granted One for All at the beginning of the show. The length of a human generation was thought to be 20 years, but current science is putting it closer to 30 years. That being said, if we take the average at 25, then quirks first appeared 225 years ago. Thus, if you remember my lesson on Evolution in Gundam, then 225 years is not enough time for quirks to spread to 80% of the human population in My Hero Academia.
“If it’s not genetic, then what is it?”
Actually, quirks are still genetic traits, but not in the more traditional sense that most people are used to and the hint comes from One for All. Bacteria can transfer genetic traits to each other without reproducing using a structure called a plasmid. A plasmid is a circular loop of DNA that can replicate independently from the cell and it can be transferred between organisms. Plasmids are typically found in bacteria and can carry beneficial traits like antibiotic resistance. (To them, not us lowly humans)
Plasmids are not limited to bacteria, and there are eukaryotic (cells that have a nucleus and organelles) plasmids, but none that are found in plants or animals. Since plasmids can be transferred without reproduction, it is possible that a eukaryotic human plasmid could spread like a virus to a large portion of the population. The plasmid could be carrying genetic information for a quirk and cause a change in the person it enters granting them a new ability.
Plasmids have one other unique ability in that they can insert themselves into the host cell’s DNA. Thus, the plasmid (quirk DNA) can be passed on by passing on the plasmid itself or by passing itself on with the rest of the parent’s DNA.
Plasmids can also explain how quirks can fuse, as seen with Todoroki, who has his mother’s ice quirk and his father’s fire quirk. Plasmids can and do change over time, and can also be engineered to contain desired segments of DNA.
One for All
If we go with the idea that the genetic information for quirks is contained within plasmids as previously discussed, then One for All is fairly easy to explain. One for All was created by the fusion of two different quirk plasmids, (a quirk that allows the user to use and stockpile power, and a quirk that allows the user to pass it on) to create One for All. Unlike some of the other quirks that have integrated into the person’s DNA, One for All remains as a plasmid. This is how it is passed onto a new user, by ingesting their DNA or cells containing the plasmid.
If you are thinking but why does the previous user lose their quirk?, then I have an answer for you: epigenetics. Epigenetics examines how the environment can influence the inheritance of genetic traits. When All Might passes on One for All, he is giving the plasmid an epigenetic message to transfer to another individual. At the same time the plasmid is sending a self-destruct message to all of the other plasmids in All Might’s body, slowly removing his ability to use One for All. Also, while Midoriya needs time to learn how to harness his quirk he also needs to give the One for All plasmid to time spread to every cell in his body furthering his ability to use his new-found quirk.
PS- sorry its been so long everyone but real life in the form of moving back home from Mongolia was taking up a lot of my time. Also you can catch me at this years Otakon where I will be presenting.