I think there's a 'balancing game' between "I need my DNA to be as compact as possible" (no waste of energy, faster to duplicate, less chance for errors) and "I

I think there's a 'balancing game' between "I need my DNA to be as compact as possible" (no waste of energy, faster to duplicate, less chance for errors) and "I need space in my DNA to allow new things to evolve". In zebrafish and mouse, the more "developmental" a gene is, the more SPACE it seems to have around it. More space means more regulation and more potential for new regulation.