There is certainly something to that. Some system (wrong word but I can’t think of a better one) decides when to or if to employ any given code in an animal’s DNA and that makes all the difference in what kind of animal is produced. Chickens’ DNA has code in it to grow teeth. What decides not to acces this code in chickens born today?
Two new concepts ~ and they explain how every animal can end up with a liver that works yet it's the right size for the animal, and otherwise works right.