Is anyone familiar with this religion/myth?

I read it somewhere a while ago and now can’t remember what book it was in. Some kind of indigenous religion I think. It said that humans used to be giants with like 108 ribs or something, and that was the age of goodness and everything was nice. With every age or era they gradually got smaller and more corrupt and unhappy ended with the age of destruction (or something).
It’s kind of vague but I just can’t remember, it’s been a while. Tried googling different combos of words but no luck there.
Any help is greatly appreciated!