Originally Posted by
vitruvian
When they fully merged Kirby's Eternals with the rest of the MU, in storylines such as the Eternals Saga in Thor, they had to integrate them with everything else. It's definitely not in Kirby's original series, but in Eternals appearances later on crossing over with the rest of the MU.
So, in Thor, they explained that the Eternals were not the same as the 'real' Olympians and Asgardians and other pantheons, but were sometimes mistaken for them... and the Eternals of Olympia led by Zuras had actually reached an accord with the Olympians of Olympus led by Zeus, where the former would sometimes act as representatives of the latter in the Earth dimension while the real 'gods' relaxed in their pocket dimension.
And pretty much everywhere else the Eternals appeared, it got mentioned that when the Celestials created the three species of Eternal, Deviant, and regular human from the proto-humans, they had inserted the potential for varied superpowered mutation into the regular humans, even though it didn't manifest in actual superhumans much until the modern day. This was meant to explain both mutants, born with their powers (even if they didn't manifest till adolescence), and characters like the Fantastic Four and Hulk and Spider-Man and Electro and so on who acquire their powers from accidents and exposure to mutagens in life. It was also around the same time that things like the Sentinels in Days of Future Past hunting down other superhumans suggested that mutants and 'accidentals' had commonalities, and that the seeds for both had been planted by the Celestials. I'm not sure why they didn't just go whole hog and say that some people with the active X-gene had their powers manifest at adolescence or birth, while others had powers that remained latent unless they met with some other form of trauma that then became their 'origin'.