How could one vital organ survive, while it is waiting for all the rest of the vital organs to evolve?
The average adult human has between 300 million and 500 million Alveoli in their lungs. Alveoli are the structural and functional units of the respiratory system, and they increase the surface area for the exchange of respiratory gases. Yes, the transfer of oxygen and carbon dioxide occurs throughout the bloodstream, primarily through the process of gas exchange where oxygen moves from the lungs into the blood and carbon dioxide moves from the blood into the lungs at the level of the alveoli, carried by red blood cells to be delivered to body tissues and then transported back to the lungs as waste.
Doesn't the heart, lungs, brain, blood stream, nervous system, muscles, digestive system, skeletal system, mouth, throat, eyes, passageways and other vital organs have to be fully developed all the same time?
How would one survive without all the others, fully developed all at the same time?