Why do dolphins have olfactory receptor (OR) genes?

[xianghua]

Uh, no, since evolution is a continuous process, and the conditions required to make said process stop do not exist, our species remaining unchanged would defy evolutionary theory entirely.

some species doesnt change even about 70-80 my (from morphological prepspective). so its possible according to evolution that a species (or a family) will stay basically the same for a very long time.

 

[PsychoSarah]

some species doesnt change even about 70-80 my (from morphological prepspective).

But they do change genetically, remember that the majority of mutations don't have a an affect on the physiology of an organism at all. Even in situations in which any morphological change is selected against, there will still be neutral mutations that enter the population and change the genotype. Mutation never ceases.

Also, if you are thinking of organisms such as coelacanths and sharks and how they are physically very similar to species that existed millions of years ago, they aren't identical to those species. You can't ignore even the minor differences of size or color, since those traits do have selection pressures that act on them.

so its possible according to evolution that a species (or a family) will stay basically the same for a very long time.

Sure, in terms of physical traits. Not in terms of the DNA directly, that will change over time to some extent no matter what. The change just might not be in the coding regions of DNA.

 

[seeker0]

I was investigating this question of dolphin OR genes myself. It would certainly be evidence for evolution. I came across a study though which found that at least some dolphin species can actually utilize those olfactory genes afterall:
Sensory Perception in Cetaceans: Part II—Promising Experimental Approaches to Study Chemoreception in Dolphins

 

[xianghua]

I was investigating this question of dolphin OR genes myself. It would certainly be evidence for evolution. I came across a study though which found that at least some dolphin species can actually utilize those olfactory genes afterall:
Sensory Perception in Cetaceans: Part II—Promising Experimental Approaches to Study Chemoreception in Dolphins

if its true that a dolphin can smell then the whole argument fail.

 

[Speedwell]

if its true that a dolphin can smell then the whole argument fail.

Well, if you leave a dead one in the sun for long enough...

 

[indopanda]

Evolution is about change. It is irrelevant as to whether that change involves an increase, or a decrease in complexity. I am amazed that you are unaware of this basic fact and yet, armed with such ignorance you choose to contest the reality of evolution. I am curious as to where you picked up this erroneous idea. Would you enlighten me?

Could you further elaborate on this point? Is your understanding that the degeneration of a complex system to the point where it loses functionality represents an example of evolution?

In the OP's example, we have a functional olfactory system that degrades over time and becomes non-functional. Is this evolution? Does the dolphin gain some sort of advantage by not having a functional olfactory system anymore?

Perhaps you could argue that the dolphin is not disadvantaged by the loss of it's olfactory system so that individuals without a functional olfactory system survived and propagated, but why did the loss of an olfactory system become fixed within the population?

Either it had to have provided a significant survival benefit or only dolphins without a function olfactory system survived for someone other unrelated reason. If the former case could be somehow proven, then perhaps we would have evolution, but if the latter is the case all we have is decay.

 

[Ophiolite]

Could you further elaborate on this point? Is your understanding that the degeneration of a complex system to the point where it loses functionality represents an example of evolution?.

Correct. The loss of functionality is due to a change in the genotype and that change, by definition, is evolution.

In the OP's example, we have a functional olfactory system that degrades over time and becomes non-functional. Is this evolution? Does the dolphin gain some sort of advantage by not having a functional olfactory system anymore?

In its new environment it appears that the olfactory system is of little benefit to the dolphin. However, its maintenance demands resources that could be better employed elsewhere. So, yes its loss would be a benefit and yes that is evolution.

Perhaps you could argue that the dolphin is not disadvantaged by the loss of it's olfactory system so that individuals without a functional olfactory system survived and propagated, but why did the loss of an olfactory system become fixed within the population?

Either it had to have provided a significant survival benefit or only dolphins without a function olfactory system survived for someone other unrelated reason. If the former case could be somehow proven, then perhaps we would have evolution, but if the latter is the case all we have is decay.

If I have a house-clean and throw out an old stove I once cooked on, along with a once serviceable chair that is now missing a leg, has the quality of my house improved, or decayed? I hope the answer is obvious and the analogy clear, but ask or challenge if they are not.

 

[xianghua]

Either it had to have provided a significant survival benefit or only dolphins without a function olfactory system survived for someone other unrelated reason. If the former case could be somehow proven, then perhaps we would have evolution, but if the latter is the case all we have is decay.

i think that in either cases there is evolution. since in both case its a genetic loss.

 

[FrumiousBandersnatch]

i think that in either cases there is evolution. since in both case its a genetic loss.

A genetic change. No genetic material is lost.

 

[xianghua]

A genetic change. No genetic material is lost.

the OR were lost.

 

[FrumiousBandersnatch]

the OR were lost.

The genes became non-functional; still available for repurposing in the long-term.