I Reincarnated into a Single-celled Organism! - Chapter 174

The difference in species play a role, as you mentioned, but you didn’t manage to accurately describe the difference. Spirit rose from a bacteria to a level 10 evolved, and according to the status window, he changes his race close to his previous race every time be evolves, which probably explains why marriages within the paragon families works. Still, the fact that humans aren’t supposed to inbreed is also probably the reason why paragon families decline if they fail to rope in people with positive mutations, because without them, inbreeding still causes a genetic downgrade. Even if you evolve into a higher form of your previous evolution, they are somewhat still related. On another note, since Spirit started as an autotroph, the very bottom of the food chain, the energy he accumulated each time he evolves might’ve made each cells in his body to be at the maximum possible density. I kind of doubt it a little since Erika mentioned a one to ten ratio between preys and predators and Spirit follows the same rule, but that all depends on whether the activation energy in this world is connected to energy density. All I’m thinking is that Spirit’s cells are packed with tremendous energy. That’s why he’s multiple magnitude stronger than those at the same evolutionary level. I hope the author confirms my theories someday.