According to the assumed evolutionary sequence of life, fish are the ancestors of amphibians. This change would require many millions of years and would involve many transitional forms.
The fossil record has been carefully examined to find a transitional sequence linking fish to amphibians, but so far such a sequence has not been found. The closest link that has been proposed is the one that allegedly exists between the fish Crossopterygii (lobe-finned fish) of the genus Rhipidistia and the amphibian genus Ichthyostega. However, there is a huge gap between Crossopterygii and Ichthyostega, a gap that would span many millions of years during which an innumerable number of transitional forms would need to reveal a slow gradual change from the pectoral and pelvic fins of the crossopterygian fish into the foot and legs of the amphibian, along with the loss of other fins and other transformations necessary for adaptation to terrestrial life.
What are the facts? Not a single transitional form has ever been found that would show a specific step between the fins of crossopterygii and the foot of Ichthyostega. The foot and its girdle in Ichthyostega were already fundamentally amphibian in type, showing no trace of any pre-existing fin.
There is one fundamental difference between all fish and all amphibians, insurmountable by transitional forms. In all fish, living or fossil, the pelvic bones are small and loosely attached to the muscles. There is no connection between the pelvic bones and the spine. No connection is even needed. The pelvic bones do not support and cannot support the body’s weight. There are no fish that walk, including the “walking fish” from Florida. This last-mentioned fish does not walk, but slides on its belly, using the same movements as in water.
In four-legged amphibians, living or fossil, on the other hand, the pelvic bones are very large and firmly attached to the spine. This is the type of anatomy that an animal must have to walk. This is the type of anatomy found in all living or fossil four-legged amphibians, but absent in all living or fossil fish. Transitional forms do not exist.
For a long time, it was assumed that the fish, which evolutionists believe was the ancestor of amphibians, went extinct about 70 million years ago. In rocks that evolutionists consider 70 million years younger, fish fossils have never been found. Around 1939, however, this species of fish was found alive and well on the coasts of Africa. It was a crossopterygian fish, genus Latimeria. It was taken from a depth of about 1500 m. It is still largely the same fish (or a closely related form) as the one believed to have evolved into amphibians, which then multiplied over many millions of years. It would be unsustainable to believe that it has remained genetically and morphologically the same all these millions of years while its ancestor evolved all the way to humans. Furthermore, how could any creature on Earth exist for 70 million years without leaving a trace in the fossil record? Something must be wrong with the evolutionary assumptions!
Why was the crossopterygian fish, the Rhipidistia, chosen as the ancestor of amphibians? First of all, there is nothing better available. In the absence of candidates for a transitional form between fish and amphibians, evolutionists studied different groups of fish. Crossopterygian fish were then adopted as the group most similar to be the ancestor of amphibians. This mostly happened due to certain similarities in skull patterns with those of Ichthyostega, possessing a complex “arch” type of spine similar to that found in Ichthyostega and other labyrinthodonts, and the presence of bones in fins which evolutionists suppose evolved into the limbs of amphibians.
According to Romer, the selective pressure that allowed the origin of four-legged amphibians from their fish ancestors is the assumption of periodic droughts that were characteristic of the Devonian period, during which it is assumed that amphibians could have evolved. This forced crossopterygian fish to leave dried-up lakes (it was believed that they had lungs along with gills) and search for other water sources. These forms, which inherited random mutational changes that allowed more efficient movement on land, survived in greater numbers than other, less well-equipped forms. Many such episodes eventually led, over millions of years, to the true amphibian.
This story, attractive at first glance, loses its acceptability when all the facts are considered. Since amphibians are found in the late Devonian, they must have evolved much earlier than the Devonian period when their supposed ancestors, the Crossopterygii, progressed. If Romer’s story is true, the Devonian period should show us the mass extinction of crossopterygian and other freshwater forms. The truth is the opposite.
In the lower Carboniferous, the other three orders of amphibians are located. Since these highly divergent amphibians appeared at the beginning of the Carboniferous with already complete characteristics, they must have developed much earlier in the Devonian, just like, supposedly, Ichthyostega. The same selection pressure, such as periodic droughts, which Romer postulates, must have acted on the ancestors of these three orders as well as on Ichthyostega, and they must have developed from Crossopterygii or Ichthyostega. However, the members of none of these three types have the “arched” type of vertebrae that Crossopterygii and Ichthyostega possess, but all have the “more primitive” lepospondylous or “scaly” type of vertebrae. How can the “arched” type of vertebrae then be used as a link between Crossopterygii and amphibians?
Further, of these three orders, Aistopoda had long, snake-like bodies with up to 200 vertebrae. Most did not possess any limbs, not even a trace of the pectoral or pelvic girdles! In some forms from the order Nectridians, the bodies were also not elongated like Aistopoda, also completely without limbs. If Ichthyostega, or some Ichthyostegid form, was the ancestor of all amphibians, then while it was in the process of obtaining quadrupedal limbs from its Crossopterygian ancestor, its amphibian descendants between Aistopoda and Nectridians were equally busy looking for a way to free them!
What selective pressures led to quadrupedal limbs in Ichthyostega, while at the same time causing its reduction and loss among Aistopoda and Nectridians? Why did these highly divergent forms appear in the fossil record already complete in diversity at their first appearance, and without evidence of transitional forms?
Three living orders of amphibians, including salamanders and newts (Urodela or Caudata); apods (Apoda or Caecilia), similar to worms without limbs; and frogs (Anura or Salientia), which are the most adapted of the land vertebrates, possessing long hind limbs, but having no tail. All of these modern amphibians possess a ‘more primitive’ lepospondyl type of vertebrae, rather than the ‘arch’ type of vertebrae which allegedly connects amphibians with their crossopterygian ancestors. Then, there are no transitional forms that would link these three modern orders constituting the subclass Lissamphibia and the amphibians found in the Paleozoic. Speaking about Lissamphibia, Romer asserts the following: ‘Between them and the Paleozoic group stands a great evolutionary gap unbridged by fossil material.’2 Nor is there any fossil record from which any evidence arises that these orders of living amphibians originate from a common ancestor.
An extremely wide gap between fish and amphibians, as observed between crossopterygii, rhipidistia, and ichthyostega, the sudden appearance, in fact, of all Paleozoic orders of amphibians with distinct ordinal characteristics complete in the first representatives, and the absence of any transitional forms between these Paleozoic orders and the three living orders, makes it absolutely impossible to believe that these forms evolved. These facts, however, are in complete agreement with the predictions of the creationist model.
- Literature
- A. S. Romer, Vertebrate Paleontology, 3rd ed., U. of Chicago Press, Chicago, 1966, p. 36.
- Romer, Ref. 1, p. 98.