Kirkasant And Krypton

"Starfog."

On Kirkasant, the refugees have a small genetic pool in a hostile environment but the latter protects them from the consequences of the former:

harsh natural selection;

high background radiation, therefore many mutations;

woman bearing constantly;

most babies and many adults dying;

the fittest surviving;

an unfilled ecological niche for intelligence;

galloping evolution;

exploding population;

the planet filled in one or two millennia.

Compare Elliot S. Maggin's (and my) interpretation of Krypton:

The Kryptonian god, Rao, a powerful superior being associated with an old red giant star, presided over a large planet with a dense atmosphere. Rock-hard plants grew on the surface and a few almost un-killable animals lived on a plateau where the atmosphere was breathable by terrestrials although other conditions, like gravity, climate and visibility, were hostile. Rao rescued shipwrecked terrestrials, placed them on the plateau and oversaw their evolution so that they increased their strength, endurance and visual range while retaining their human form...

In Superman: Last Son of Krypton, a novel by Elliot S. Maggin, human beings have spread to various planets, we are not told from where. On Krypton, “…two stranded space wanderers found each other…” and began to populate the planet. (1) 

 

Because of the “monstrous” gravity, drastically changeable weather and poor visibility:

“The race’s physiology was subtly altered while outward appearances changed very little…” (2)

With denser muscles, sharper reflexes, broader perceptions and wider optical capacity but unchanged appearance, Maggin rationalises Superman’s human appearance and superhuman powers. (3) However, I think that outward appearances would change under such conditions unless Rao controlled the adaptations.

My “Last Son of Krypton” scenario is an adaptation of Maggin’s.
-copied from here.