The OC is maybe referring to Larry Niven’s ring world, in which a race of humanoids called the Pak which resemble real life elderly people, only with armoured joints and immortal, have a life cycle where their offspring are humans. Once reaching old age, pheromones given off by a certain type of tree that bear a fruit similar to an apple, cause the humans to be overcome until they eat the fruit, at which time they metamorphize into an adult Pak, increasing intelligence massively and lifespan. In the book, the humans of earth stay as the larval stage as the “Tree of Life” were never planted (or never produced the correct fruit, I can’t recall) on our planet as there wasn’t the right kind of minerals to support it.

The Pak went about colonising planets and they left their offspring on earth when they discovered radiation coming from the centre of the galaxy that was changing the genetic makeup of their offspring, causing the adult Pak to murder their own offspring and all sorts of wars.

The Pak built a massive ringworld (think Halo) because that’s easier than colonising a planet apparently, but their offspring started to mutate wildly into different offshoots of humans, pygmies, humans with gills, etc.

It’s a good series and enjoyable to read but it’s not a particularly serious story. One of the aliens is depicted as being some sort of hand puppet with legs. Super odd stuff.