Many people think that birds evolved from reptiles, probably lizards. It is hard to understand why they believe that, since birds and reptiles are different in so many ways, both inside and out.
Reptiles are cold-blooded. That is, their bodies are the same temperature as their surroundings. Birds and mammals are warm-blooded. Their bodies can make heat to keep them comfortable unless it is very cold. They can also cool off if it is too warm. Only creatures with four chambers (rooms) in their hearts are warm-blooded. Birds as well as people and all other mammals have four-chambered hearts. But reptiles have three-chambered hearts. The arrangement of bones in the body of a reptile is entirely different from that of a bird. For instance, only birds have wishbones.
A bird's face is nothing like that of a reptile. Only birds have beaks. Fish, reptiles, amphibians and all mammals, including people, open their mouths by lowering the lower jaw. The upper jaw cannot be moved. It is part of the face. But birds can lift the upper beak (mandible) as well as lowering the lower one.
We are told that birds and reptiles are alike in that both lay eggs. But so do insects, amphibians, most fish, and two kinds of mammals. Eggs of different kinds of creatures are different from each other. Bird eggs have brittle shells. Reptile eggs have leathery shells. All birds lay eggs, but not all reptiles do. Some reptile babies (lizards and snakes) are born like the young of mammals.
The most noticeable difference between birds and reptiles is that birds have wings and reptiles (most of them) have four legs. How would a front leg turn into a wing? Someone has actually suggested that at one time there may have been a creature like the one in the picture above. He thinks some birds might have grown a few feathers on their front legs and used them for catching insects. Most of them would get away before it could get them into its mouth! It wouldn't run well, off balance like that. It couldn't fly, or climb a tree, or run into a hole in the ground. How would it get away from its enemies?
How would one kind of creature change into another? What would change first? If the changes came about by chance some of them would go in the wrong direction. There would have to be someone to direct the changes so they would come out right. But anyone wise enough and capable of doing that would also be wise enough to make the creature right to begin with, and not have to bother with all that changing.
by Mina Arnold Young
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