Posted: Dec 06, 2020 9:16 pm
The theory of evolution has an enormous amount of confirmatory evidence and I do not question its scientific usefulness. But the explanations offered thus far still leave puzzling questions. The concept of "conversion" (that significantly divergent genetic lines can develop similar structures due to similar environmental conditions) is, of course, a description, not an explanation.
The discussion of Hox genes is getting closer to explanation. Hox genes turn on or off the development of various genes in different segments of the developing organism. How and why this operates is not fully understood. Different segments have specialized genes for different functions. The first segment has genes for developing head structures. for example, sight, taking in air or food. It is unable to develop legs. The next segment can grow legs, but not sight. A middle section can grow a gut but not legs, etc. There can be great variability within a section over time governed by Hox genes turning on or off genes already in that section. Of course mutations can also occur by accidental gene mutations or by environmental radiation, etc. But even these modifications are limited in scope. They cannot change a stomach gene into an eye gene. What usually results is a mutant that is not environmentally fit.
So how did the dorsal fin of of the cetaceans evolve? Some genes during evolution do become inactive as a particular feature may no longer be useful. Five toes of early horses became useless as the horse developed hooves but the five toes gene still exists in a dormant state and could be reenacted at a future time. But the dorsal fin gene is not to be found at any time in the evolution of mammals. It was suggested that the gene might have been carried dormant from mammal's fish ancestry. Possibly but not plausible. Fish fins are boney structures and found on various parts of the body. Dorsal fins are fleshy and found on only one area. Furthermore, the other cetacean appendages developed from leg and tail bone structures already highly developed in prior mammals. The dorsal fin is totally unique. It is not boney and is located on the gut segment of the body that never had any appendage genes during the whole of mammal evolution.
Although the Orca's fin might help in stabilizing motion, It is difficult to understand how a small "accidental lump" could in anyway be beneficial to survival. A small lump provides no stabilization benefit, thus no survival benefit and, therefore, no natural selection could promote its further development.
I have not come across any answer to this question. I'm still looking. But please don't just say that "evolution explains it".
The discussion of Hox genes is getting closer to explanation. Hox genes turn on or off the development of various genes in different segments of the developing organism. How and why this operates is not fully understood. Different segments have specialized genes for different functions. The first segment has genes for developing head structures. for example, sight, taking in air or food. It is unable to develop legs. The next segment can grow legs, but not sight. A middle section can grow a gut but not legs, etc. There can be great variability within a section over time governed by Hox genes turning on or off genes already in that section. Of course mutations can also occur by accidental gene mutations or by environmental radiation, etc. But even these modifications are limited in scope. They cannot change a stomach gene into an eye gene. What usually results is a mutant that is not environmentally fit.
So how did the dorsal fin of of the cetaceans evolve? Some genes during evolution do become inactive as a particular feature may no longer be useful. Five toes of early horses became useless as the horse developed hooves but the five toes gene still exists in a dormant state and could be reenacted at a future time. But the dorsal fin gene is not to be found at any time in the evolution of mammals. It was suggested that the gene might have been carried dormant from mammal's fish ancestry. Possibly but not plausible. Fish fins are boney structures and found on various parts of the body. Dorsal fins are fleshy and found on only one area. Furthermore, the other cetacean appendages developed from leg and tail bone structures already highly developed in prior mammals. The dorsal fin is totally unique. It is not boney and is located on the gut segment of the body that never had any appendage genes during the whole of mammal evolution.
Although the Orca's fin might help in stabilizing motion, It is difficult to understand how a small "accidental lump" could in anyway be beneficial to survival. A small lump provides no stabilization benefit, thus no survival benefit and, therefore, no natural selection could promote its further development.
I have not come across any answer to this question. I'm still looking. But please don't just say that "evolution explains it".