Hens are like dinosaurs too, I heard one yesterday screaming like a velociraptor from the movies xD.

Interesting that theory about iguanas, I might keep an eye on them to see if they change. I've noticed them being grey when old, especially in the dry season, and they are bright green when they are young, especially in the rainy season. And they do be happier in the rainy season when there is so much to eat, and drink, and many places to hide.