[Terretta]

Ha, literal "chicken and egg" framing.

OK, your idea is parent optimized for physical characteristics of progeny, or in this case, the parent is formed by the egg, not the egg by the parent?

In this article, your point would be, because of laying conical eggs, certain species of birds were able to nest on cliffs. So their eggs not rolling made them cliff dwellers?

And similarly, elliptical eggs optimized their mothers for faster flight?

Not sure. Put like that, I'm thinking it's reasonable the parent trying to roost on the cliff came first.