It merely means they are all descendants of the first tetrapods. On the other hand, the fact that all have one bone in the lower jaw, and three bones in the middle ear, demonstrates that they all evolved from a common ancestor that was a primitive mammal.
Because it makes no sense for God to build genes for reptile ears and jaws into mammals, and then add some more genes to make them inoperative, if He designed each one from scratch. On the other hand, it makes all sorts of sense if He used nature to evolve new species from old.
Couldn't primitive mammal been a prototype for others to follow?
If God wasn't omnipotent, that might make some sense. The "space alien designer" of the IDers, for example, might do that. The omnipotent and omniscient God of the Bible would have no use for prototypes.
Why would it be necessary, if all wee to eat and hear, for all to be put together differently?
Because it works differently for mammals and reptiles. They don't hear so well, and much of what they hear is low frequency sound that is transmitted though the ground to their lower jaws and then to the middle ear. Mammals have much sharper hearing and can pick up higher frequencies, because the three-lever system in the middle ear of mammals is much more sensitive and efficient.
If you take some steel, and rubber, and a tank to hold fuel, and a reservoir for oil you can get anything from a motor car, aeroplane, motorcycle, a farm tractor, train, and even some boats. None of these came from the other yet they all require steel, rubber, a fuel tank, and oil reservoir.~ along with variations in each design. Each came about on its own.
The materials are not the genes. And what we see in biology is quite different. If it worked the same in engineering as in biology, you'd see rudimentary propellers on jet planes, horse harnesses on automobiles, and useless hand cranks on electric drills, perhaps modified to become hanging hooks.
You reply to the human spirit question with
'You're right. God says we came from the earth like other animals. But then, He gives each of us our souls directly, making us different from all the others."
"Yep. Our bodies show their evolution from other living things, but our souls do not. And that is how we are in the image of God."
There does not have to be an evolution in place. We could well have been made, as it was said within the Holy book.
Of course we were made. It's just that scripture doesn't say how. The evidence shows that we evolved from other animals.
For there is no reason for an evolved being to be selected for a human spirit which has an end in eternity different then the original intent of that primitive mammal.
All we know is that it happened, and continues to happen. And it's impossible to know what God's purposes may be in doing it as He did. I can only be confident that it was the best way, since it was pleasing to Him.