While reading through DC lore, I came across speculation that Kryptonians (and even the Daxamites) may not be truly alien in the traditional sense. Instead, their origins could trace back to Earth during the golden age of Atlantis, when that civilization was at the peak of technological and scientific prosperity.
According to this idea, the Atlanteans once built fleets to explore the stars. But after Atlantis sank, those fleets were left stranded in space with no home to return to. The survivors were forced to seek out habitable worlds, where they eventually settled. Some found Krypton, while others found Daxam. Over time, either through genetic engineering or natural adaptation, these human offshoots evolved into entirely new civilizations.
This brings me to Krypton's unique biology and their connection to the sun. In Man of Steel, we see the Codex (the foundation of their genetic engineering) encoded within the structure of a human-like skull—smaller than an adult, but about the size of a child's. This opens an interesting possibility: what if the Kryptonians' genetic template wasn't just their own, but drawn from a divine or alien source?
In Kryptonian religion, Rao—the god of the sun—is central. If the Codex was derived from the DNA of a god (perhaps even Rao himself or a being of his species), it could explain their strange relationship with sunlight. Their bodies might be attuned not merely because of evolution, but because they were engineered to channel divine power through solar energy. In this sense, the yellow sun awakens their godlike potential, while Krypton's red sun may have been Rao's own design: a cradle that nurtured them, but also a chain that lulled them into obedience, keeping their true power dormant until needed.
If this is true, then Kryptonians are essentially humans enhanced with the DNA of a godlike being. That would explain why their biology reacts so explosively under different suns. It might also shed light on why Krypton's ruling council eventually banned natural birth: they feared what they were—or Rao himself feared what they could become. Billions of godlike beings roaming the galaxy unchecked could have provoked endless war, conquest, or even the wrath of higher gods. Keeping Kryptonians confined to their world may have been less about isolation, and more about containment.
What do you think? Could Kryptonians be the descendants of Atlantean explorers, forever tied to Earth's lost history, and empowered—yet bound—by the DNA of their sun god Rao? Or does this stretch too far beyond DC's intended lore?