I do not know for certain how they developed but I know several herbivorous dinosaurs were thought to have rudimentary gizzards. The evolution of a gizzard eliminated the need for sharp teeth and thus were lost. Birds are thought to be descended from herb. dinos so this makes quite a bit of sense to me.
"I do not know for certain how they developed but I know several herbivorous dinosaurs were thought to have rudimentary gizzards. The evolution of a gizzard eliminated the need for sharp teeth and thus were lost. Birds are thought to be descended from herb. dinos so this makes quite a bit of sense to me."
As long as they had sharp teeth, there was no need for the gizzard. So the animals decided to eat stones to dull their teeth so they could eat plants? Doesnt't maake sense to me, might to you.
Back to the old question, WHAT CAME FIRST, THE CHICKEN OR THE EGG.
Evolution sounds a lot like the "invisible hand" in the Wealth of Nations by Adam Smith.