Jan Ardena
Yes. Mammals all originated as land dwelling creatures with four legs, period. In fact they all descended from mammal-like predecessors not much different from a rat(and not aquatic at all)some 200 million years ago. All mammals currently evolved to live in water descended from mammals that did not live in water, just like the penguin descended from birds that flew through the air, not the water. That is the very definition of macroevolution being the result of many microevolutionary changes such that they are no longer able to occupy the same niche(land dwelling ungulants)as their ancestors. Just like the penguin, whale ancestors were once creatures occupying an entirely different environment(dry ground)from that they occupy today(ocean only), with major changes having occurred in their morphology to allow that to happen. If macroevolution has a meaning, that's it.
It wasn't. Pakicetus was Pakicetus, not a whale of any sort, just like a chimp is not any sort of man. Pakicetus was a land dweller, maybe a river creature like the Hippo. But Pakicetus did have traits that we now see on modern whales, and the various fossils of creatures that descended from Pakicetus(ie having the Pakicetus traits plus new ones also seen on modern whales)have more and more whale-like traits as time passes. Eventually the descendants accumulated ALL the traits that distinguish whales, THEN it was a whale. An instance of parallel evolution is the manatee, it has already lost it's rear legs(just like the whales did millions of years ago), it is well on it's way to being another whale-like mammal, as are sea lions. They will never be whales, but form follows function and any underwater mammal will tend to look similar as their evolution continues.
The fossils have traits that show up in subsequent descendants, like having no back legs or various stages of losing those legs or nostrils on the back of the head, or creatures with intermediate position of the nostril showing a progressive move to the back of the head. We know we descended from amphibians because we still have the skeleton, bone for bone, that they developed first(and which was available ONLY to the amphibian's descendants).
No, there are the facts of the matter and the one side that deals with those facts and the other that tries to deny those facts because it conflicts with their religious beliefs. There is the informed and logical side and then there is everything else. Your OPINIONS on the matter mean nothing if you aren't dealing with reality. The Biblical view/story of the history of life is false, but how could we expect anything else when it was written by scientifically ignorant, ancient sheep-herds not really concerned with such topics. Those pushing views based on that are simply wrong. So, no, there are not two equally valid sides to this debate.
Grumpy
Is the evolution of the whale an observed fact?
Yes. Mammals all originated as land dwelling creatures with four legs, period. In fact they all descended from mammal-like predecessors not much different from a rat(and not aquatic at all)some 200 million years ago. All mammals currently evolved to live in water descended from mammals that did not live in water, just like the penguin descended from birds that flew through the air, not the water. That is the very definition of macroevolution being the result of many microevolutionary changes such that they are no longer able to occupy the same niche(land dwelling ungulants)as their ancestors. Just like the penguin, whale ancestors were once creatures occupying an entirely different environment(dry ground)from that they occupy today(ocean only), with major changes having occurred in their morphology to allow that to happen. If macroevolution has a meaning, that's it.
How do you know that the skull of the pakcetus was a primitive whale?
Was there any way it could not be a primitive whale?
It wasn't. Pakicetus was Pakicetus, not a whale of any sort, just like a chimp is not any sort of man. Pakicetus was a land dweller, maybe a river creature like the Hippo. But Pakicetus did have traits that we now see on modern whales, and the various fossils of creatures that descended from Pakicetus(ie having the Pakicetus traits plus new ones also seen on modern whales)have more and more whale-like traits as time passes. Eventually the descendants accumulated ALL the traits that distinguish whales, THEN it was a whale. An instance of parallel evolution is the manatee, it has already lost it's rear legs(just like the whales did millions of years ago), it is well on it's way to being another whale-like mammal, as are sea lions. They will never be whales, but form follows function and any underwater mammal will tend to look similar as their evolution continues.
How do you know the fossils have anything to do with the animals in question?
What are the clear lines?
The fossils have traits that show up in subsequent descendants, like having no back legs or various stages of losing those legs or nostrils on the back of the head, or creatures with intermediate position of the nostril showing a progressive move to the back of the head. We know we descended from amphibians because we still have the skeleton, bone for bone, that they developed first(and which was available ONLY to the amphibian's descendants).
There are two sides to this debate, those distinctions do well to keep that in mind.
No, there are the facts of the matter and the one side that deals with those facts and the other that tries to deny those facts because it conflicts with their religious beliefs. There is the informed and logical side and then there is everything else. Your OPINIONS on the matter mean nothing if you aren't dealing with reality. The Biblical view/story of the history of life is false, but how could we expect anything else when it was written by scientifically ignorant, ancient sheep-herds not really concerned with such topics. Those pushing views based on that are simply wrong. So, no, there are not two equally valid sides to this debate.
Grumpy