Final answer:
The advantage of four-chain hemoglobin is increased stability and functionality, leading to efficient oxygen transport and binding of other molecules.
Step-by-step explanation:
The advantage of the single chain globin molecule giving rise to the four chain hemoglobin used by humans and other animals today is increased stability and functionality.
By having four globin chains, hemoglobin is able to bind to and transport oxygen more efficiently. The presence of multiple chains also allows for the binding of other molecules, such as carbon dioxide.
Furthermore, the four-chain structure of hemoglobin provides increased stability, allowing it to withstand changes in pH and temperature, and ensuring that it can perform its function effectively in the diverse environments of the body.