Humans, like other warm-blooded animals, expend a lot of energy and need a lot of oxygen. Our four-chambered hearts make this possible. It gives us an evolutionary advantage: We’re able to roam, hunt and hide even in the cold of night, or the chill of winter.
Now scientists have a better understanding how the complex heart evolved.
The story starts with frogs, which have a three-chambered heart that consists of two atria and one ventricle. As the right side of a frog’s heart receives deoxygenated blood from the body, and the left side receives freshly oxygenated blood from the lungs, the two streams of blood mix together in the ventricle, sending out a concoction that is not fully oxygenated to the rest of the frog’s body.
Turtles are a curious transition — they still have three chambers, but a wall, or septum is beginning to form in the single ventricle. This change affords the turtle’s body blood that is slightly richer in oxygen than the frog’s.
Birds and mammals, however, have a fully septated ventricle — a bona fide four-chambered heart. This configuration ensures the separation of low-pressure circulation to the lungs, and high-pressure pumping into the rest of the body.