::If you piece apart the chemical pathways, it is a given that losing a small part of that pathway will render it useless. However, incomplete parts of that pathway can serve different purposes inside the body, meaning that they still have a reason to be selected for. | ::If you piece apart the chemical pathways, it is a given that losing a small part of that pathway will render it useless. However, incomplete parts of that pathway can serve different purposes inside the body, meaning that they still have a reason to be selected for. |