The respiratory system of birds is rather unique. Mammals, amphibians, and reptiles have a two-way lung system. When air is taken in, it goes down the trachea, through the bronchi, and into the lungs. When air is exhaled, it just goes out in the opposite direction of how it was inhaled.
A bird has an elaborate system of nine air sacs throughout its body as shown in the diagrams. Its respiratory system has a one-way lung system and its lungs do not expand. Inhaled air goes down the trachea, through the bronchi, into posterior air sacs while stale air enters its anterior air sacs, waiting to be exhaled. When exhalation occurs, all air sacs collapse, forcing the stale air up the trachea and out of the body as inhaled air is pushed into the lungs. This causes a continuous flow of air through the bird lung so the lungs remain rigid and don’t expand.
If air sacs as seen in birds were to ever develop in mammals, amphibians, or reptiles, this would be a mutation creating dead space in their respiratory systems which would cause deficiencies in the flow of air through the lungs leading to death. Such air sacs would be prone to burst and air would escape out of the respiratory system into other tissues. If an embryo in these animal groups developed such air sacs, the lungs would either fail to develop causing the death of the embryo, or it would lead to deformities in other systems of the body, or render lungs prone to severe lung disease. Furthermore, lungs that expand like the lizard’s could not survive morphing into a rigid lung like the bird lung because this would kill the animal.
Pterosaurs and some bipedal (walking on two feet) land dinosaurs have evidence of possessing air sacs in their abdomens like birds, so Darwinian scientists have concluded these dinosaurs probably became birds. But the construction of the bird’s joints throws a monkey wrench into this theory. The joints in birds cause each rib to have two sections. One section connects to the spine, while the other connects to the breast bone. Such joints allow birds the flexibility to move their chest wall outwards and backwards.
These joints make it possible for any air sacs in the abdomen to inflate. And here’s the kicker–none of the dinosaurs having evidence of air sacs in their abdomens possess these special joints so their air sacs could not inflate. But that’s only part of the problem of their theory.
Air sacs in the abdomen would collapse from negative pressure from chest expansion if they are not provided the correct rigid support. Birds don’t have this problem because their femurs support the side of their abdomens and it hardly moves. This is due to the fact that a bird’s movements rely on the knees and ankles so the femur remains virtually stationary. This gives the required rigid support to the air sacs.
On the other hand, femurs in bipedal dinosaurs were moveable and would not have given the rigid support necessary to prevent the collapse of the air sacs in their abdomens. So scientists have concluded that air sacs in the bipedal dinosaurs would have been minimal and could not have functioned to move air through the lung system as the air sacs do in birds. Therefore, dinosaurs could not have had the same type of respiratory system as birds.
When you add to all of these facts that there are no transitional fossils demonstrating how dinosaurs evolved into birds, the truth becomes rather clear. Birds didn’t evolve. They were made in the same form as they appear today. Dinosaurs were also created separately and they were created after the birds. And that truth is revealed in Genesis 1:21-25–
“And God created great whales, and every living creature that moveth, which the waters brought forth abundantly, after their kind, and every winged fowl after his kind: and God saw that it was good. And God blessed them, saying, Be fruitful, and multiply, and fill the waters in the seas, and let fowl multiply in the earth. And the evening and the morning were the fifth day.
And God said, Let the earth bring forth the living creature after his kind, cattle, and creeping thing, and beast of the earth after his kind: and it was so. And God made the beast of the earth after his kind, and cattle after their kind, and every thing that creepeth upon the earth after his kind: and God saw that it was good.”
Source: Sodera, Vij. One Small Speck to Man: the Evolution Myth. 2nd revised edition. Vija Sodera Productions, 2009, pages 303-308.
–posted by Harry A. Gaylord–