Does Neo-Darwinian evolution require change ?

Something like what you're describing has been observed in "Darwin's finches", where the average phenotype tracks the climate. But this does not (common sense would suggest) involve the alternate fixation of new mutations, just a shift in the frequency of existing alleles.Something more like what you're talking about can be seen in antibiotic-dependent bacteria. I understand that if you take their antibiotics away, it is usually (but not invariably) the case that some bacterium will revert to being merely tolerant of the antibiotic, resulting in the survival of the population. In this case we are talking about mutations becoming fixed, and obviously this could happen several times in a row if you kept on jerking the bacteria around.Of course there's no particular reason why anything which at the same time is fixed by drift should also revert, so the whole genotype needn't get back to exactly where you started.--- I'm not sure where this is going.

Me neither.The question you pose is an interesting one. How much evolution would we see in an old species in a perfectly stable environment?well, adaptive evolution would stop, and genetic drift will go on happening. Now it should be pointed out that a variation which is neutral is not necessarily without consequences.When we use Darwinian algorithms to solve a problem, the solution goes to a local optimum (which we hope will be the global optimum) and stays there. this would suggest on the face of it that this is what would happen in real life. But in such algorithms the characters on which the program is operating are usually relevant ones. If we're trying to produce a design for the acoustics of a concert hall (to take an example at random) then what we're evolving is the shape. If we made the color one of the characters evolving, then being irrelevant to the fitness of the solution, it would vary at random.Now, the existence of cryptic sibling species sharing the same environment shows that such variations can produce speciation. In a way this is interesting, and in a way it isn't.What about variations which have a visible effect on the phenotype? That's more tricky to think about. Are there, in fact, variations which would be both obvious and selectively neutral?It has been suggested that we can see this in ammonites. The shape of their shells can be more or less smooth or ribbed or bumpy, and certainly varies over time which is why they make such nice index fossils. and yet there doesn't seem to be a pattern or direction to the variation.It could be, however, that we are ignorant of the underlying causes. We might speculate that this is a form of Red-Queen's-Race style adaptation which we could understand if we correlated it with the shape of the teeth of their major predators. Or perhaps it is a side-effect of some adaptive change. Maybe they were changing their biochemistry to try to get one step ahead of some bacterial parasite, and this just happened to change their external form as an incidental consequence. Such a group is more accurately described as a Lazarus taxon, and they're usually not "almost identical" after a long period of time. This is what we would expect. Once a species has evolved to fit its environment, there's no selective pressure any more, and if the sort of visible morphological neutral drift I've been discussing doesn't happen, then stasis is what we would get.Edited by Dr Adequate, : No reason given.

Well, perhaps sometimes it does.But in the first place it would have to be neutral to avoid selection, and in the second place, how many morphological mutations do you see?

Since this is contrary to observation, the sensible conclusion is that you are overestimating the frequency of deleterious mutations.

Hold on a minute.Cost of selection usually refers to the wastage involved in getting a beneficial mutation from one in the population to fixation --- that is, the cost of adaptive selection.The cost of getting a deleterious mutation from one in the population to zero is obviously much lower. Conservative selection is easy.Cost of selection as the phrase is usually used has nothing to do how hard it is to maintain stasis. Now if you want to use the phrase in a broader sense, and will stipulate as much, then that's fine --- but in that case it is no longer "obvious" that cost of selection places any stringent limit on what natural selection can do.Edited by Dr Adequate, : No reason given.Edited by Dr Adequate, : No reason given.

So learn some imperative programming language such as C or Pascal and then you can do it yourself. You can take a set of assumptions about evolution and see how they work out. I can do that and set the program to find out what happens on average in 10000 cases over 10000 generations and get a result back while I'm slicing up the vegetables for dinner. Computers are really quite fast nowadays.Do it yourself. See what happens.I have.

But that is not the limit of purifying selection. The minimum genetic casualties required to remove a new deleterious mutation from the gene pool is one (1) (ONE). Which keeps the population stable at least with respect to that particular mutation.

So we'll get neutral drift, which is technically evolution but not in the interesting sense of the word, and which needn't show up in the fossil record.

Which can still be neutral. As would all I've said on the subject, especially the things I said about purifying selection.

Where were these figures pulled from? It is far from obvious, and indeed there will always be a population size above which it is false.And this, perhaps, explains why what you think should happen in principle is the opposite of what we observe happening in practice.

No.Some of what you quote isn't even English. Look at it. "Most genetic information is transacted by proteins". Does that have a meaning? OK, what about: "The extent of non-protein-coding DNA, traditionally thought to be junk, increases with increasing complexity"? These are all English words, and yet if you put them together in that order they do not convey anything, true or false.If this is a fair sample of Mattick's ideas, then he doesn't have any ideas --- good or bad. His writing is, in the words of Wolfgang Pauli, "not even wrong".

Now that is meaningful.