Many previous quotes made it sound like the fish lost their scales in the first place because it was advantageous to them, which isn't true. When I used the term de-evolution, I was trying to counter that position, not make it seem as though there was a definite end goal to the loss of their traits. I was also not implying that more complex creatures are more evolved, because that is certainly not true. Viruses, one of the organisms that interest me the most, are very highly evolved (although that is also poor language choice), but many contain only a few genes.

I was trying to use language that could easily communicate the gist of my argument, and had to sacrifice some accuracy to do so.

tyr540

kurwinsky

The conservation of genes, rather than their elimination, pretty much guarantees that a given genetically determined trait (wings in one group of insects, perhaps bony plates in Sticklebacks) can be expressed again (re-expressed, re-evolved, whatever), or not, when that variation in expression is advantageous to survival. (As noted earlier, such expression may be epigenetically mediated in response to environmental conditions.)

Reversible expression of genetically determined traits, while its character should not be confused by use of the turn of phrase "de-evolution", should not be discounted or denied. It might rather be expressed as evolutionary reversion, to signify reversion to a form which evolved earlier in the organism's phylogenetic history.

In the case of the "wingless" gene, a new genetic component, when left turned on, produces wingless insects, eliminating a previously present morphological feature. If evolution is carelessly regarded as resulting in increasing complexity, this could be - mistakenly - considered reverse or de-evolution. The switching off of the gene (genetic "de-evolution") restores the wings (morphological re-evolution). To me this pretty much settles the need to avoid the use such terms altogether.

JimPivonka

Whether or not mutation is required for such switching to occur may vary with the trait being expressed. Some gene expression switching is epigenetically determined, rather than genetically. And epigenetic switching has been shown to be, at least in some instances, triggered by environmental factors.

It can be posited, and testable hypotheses could be devised to determine whether this instance of variation in the stickleback population may not be the result of genetically determined evolution (in the sense of changes to the Stickleback genome) but rather of environmental influences triggering epigenetically determined changes in the expression of existing genes. An interesting piece of work that would be, and very useful to the progress of genetic science.

Epigenetic variation is generally discussed (my observation) as affecting ontological development - that is the expression of genes in the post fertilization development of individual organisms, most often in through changes in the structure/function of particular organs/tissues.

The extent to environmentally triggered epigenetic changes in gene expression may also affect germ plasm, and so result in inheritable variations in the species population (phylogenetic variation) may an unwelcome question to adherents of standard genetic models. (A possible hangover from the need to refute and discredit Lysenkoism?) But considering the survival advantages that the ability to inherit changes to in gene expression in response to environmental change would confer to a genome, the evolution and conservation of such a capability should not be unexpected.

This reasoning would also apply to epigenetically triggered changes in an organism's genetic code itself (as distinguished from "simple" switching on and off of gene expression). It is not unreasonable, from a bioenergetic point of view, to posit the survival advantages conferred to a genome by the evolution of mechanisms which increase genetic variation when that organism is under environmental stress.

Such a mechanism, even though only posited and speculative, could be an explanation for a frequently observed phenomenon in organic evolution referred to by some as "late stage divergence" - as in the case of the ammonites where the period just before extinction (possibly the result of environmental changes) included a proliferation of new and in some cases quite atypical and odd morphologies.

JimPivonka

Oh my how wrong I was. You folks have no idea how happy you've made me simply by knowing that evolution doesn't run "forward" or in "reverse," but rather it just happens as a response to various environmental factors over time.

Call me easy to please, but in current American society even little victories like this can be hard to come by.

ThatGuyOverThere

Numerous

frndlybnny

Old fishies -- glowing
New fishies -- extra crunchy

RhymePhile

marvolvox

Jeff-Minor

Sorry... lost my train of thought. Fish?

Yonderboy

The responsible gene has always been there - it's just whether or not the gene was active in a particular fish or not. The more that have it active, the longer they survive, the more they reproduce, the more have the active gene...and *viola* - armored fish are the majority and not the exception.

InfiniTrent

Asari

beercheck

Ann and Jeff VanderMeer

Jeff-Minor

j0hnnyb

I love getting to a post late in the game and finding that quetzilla, soul, botanicidal and grey area already made the salient points.

Goodnightbabytron

russdanger

I totally agree that sometimes organisms change because there is no longer any reason to continue growing certain phenotypes. Fish and amphibians which have migrated into caves often lose their eyes because they no longer need them. Genetic drift is another instance where species can lose traits.

But neither of those things are "de-evolution". Eyes aren't universally better than no eyes. It all depends on the environment. Using the term "de-evolution" continues the perception that more advanced organisms are just accumulations of more and more adaptations. This simply isn't true. An earthworm is just as evolved as a human. We have each found a niche in the environment and have evolved as much as necessary to fully exploit that niche.

TheRealVeon

Jeff-Minor

Presumably, the pollution killed many/most of the fish, except those that were able to cope with the pollution. Would those have been the ones with less plating? Before the lake became polluted, did all/most of the fish have plating? I doubt that is the only factor that allows fish to survive sudden pollution. Surely there are other traits that contribute.

Additionally, the rapid evolution towards additional plating when pollution was reduced would have been encouraged by the improved conditions of the water. Cleaner, healthier water would mean healthier fish, who spawn an increased number of healthier fish, and so on, resulting in a greatly increased population with greater variation. Once the predator population increased (as a result of the cleaner water and the greater food source of soft, un-plated fish), the result would be a greater proportion of sticklebacks with more plating, which results in further generations of sticklebacks with more plating. And so on.

What about the predator fish? Are they evolving towards sharper teeth or stronger jaws, to better combat the increased armor of their prey?

Everything is connected!

StokerGiles

nygenxer

justhesh

"The ability of the fish to quickly adapt to environmental changes such as increased predation by the cutthroat trout is due, Peichel believes, to their rich genetic variation. The sticklebacks in Lake Washington contain DNA from both marine (saltwater) fish, which tend to be fully plated, and freshwater sticklebacks, which tend to be low-plated. When environmental pressures called for increased plating, some of the fish had copies of genes that controlled for both low and full plating, and so natural selection favored the latter."

In other words, natural selection killed off all the sticklebacks that didn't have the genes required to survive. That is evolution. Just because the genes required to survive are throwbacks doesn't mean it is "de-evolution."

Ghede

justhesh

1. Water cleared - lots of sticklebacks got eaten.

2. A few better-plated fish survived just a bit longer than their brethren - breeding similarly plated offspring.

3. Of these offspring, a few better-plated fish survived a bit longer than their brethren - breeding even more similarly plated offspring.

4. Rinse repeat

....

57. Voila - fully-plated sticklebacks.

I think it's also a bit misleading to say the fish "adapted" to their new environment.
Evolution doesn't let you adapt - it just favors those lucky enough to be lucky enough.

SoulCarnival

Certainly those efforts must come in the wake of careful consideration.

justhesh

taxbaby

I think this would be more an example of a failed mutation than evolution in progress. A mutation occurred causing the sticklebacks to lose their plating, the trait proliferated, then the environment altered, causing the loss of the plateless variety rather suddenly and allowing the plated variety access to the resource base of the then-diminished plateless population, aided by their lower death-rate.

LTerminus

Calraigh

Also, while de-evolution is a misnomer, the idea isn't as unreasonable as most people are portraying it to be. A lot of times evolution happens not because there is an incentive to change, but because there is no reason not to. When mutations in genes are no longer relevant to the continued survival of an animal, chance mutations that don't help the animal in any real way can spread, and can cause animals to revert to more primitive states. The reason why the fish lost their plates is the same as the reason why animals in caves go blind and become colorless.

It would be evolution if they lost old adaptations because they were harming their survival ability, but they aren't. They are losing those adaptations because it is no longer necessary for the species to maintain them, not because getting rid of the confers an advantage. In cases like the original loss of the armor plating, the case could be made that fish are "de-evolving."

tyr540

PadreFaustus

Annalee Newitz

Grey_Area

These fish clearly must be destroyed to preserve the natural order.

Palliard

That's exactly the issue. Evolution and genetics are not inherently related. Genes and the processes that affect them are simply one aspect of the how the larger process of evolution occurs in the world. The main process is: shit happens and you mate and/or die.

As far as the fish go, you could say that it's something of an atavistic re-adaptation, but reverse evolution just doesn't exist. Evolution is like Entropy, it's directly tied into the concept of time moving forward. 'Reverse evolution' would just be watching time go backwards, and that doesn't actually mean anything.

quetzilla

ceriphim

The fish had extensive boney coverings.. which they lost...

They then gained them back...

It would be cooler if the fish had gone from boney to no bone cover and back.. but still this is cool anyways...

It is only reverse because it is a re-introduction of a gene that had be pushed down...

Most likely the genes for armor incompletely partial recessive.. Before when it was murky the armored fish offered no benefit (and some harm assume the swam a little slower) now.. the armor favors fish with two copies of the armor gene so the do better and the fish no armor genes are fishfood...

DocGratis

snodipous

I think the thing to take away is the idea that there is no universal "positive" adaptation. No armor was the best trait for the older fish because they didn't need it, and to make it would be a waste of metabolism. Now that they are more visible, armor is a acceptable trade off for the increased energy put in to growing the armor.

Again, neither trait is "better" or "more evolved" than the other. Both serve the purpose of helping the fish survive.

TheRealVeon

SW-2

However, Annalee, if you get it on with Mr. Wings-and-magic-powers, maybe some of your children will be more fit.

marvolvox

quetzilla

Not that I believe that, I'm just putting it out there.

Dillenger69

(padding of said room optional)

bigswingdaddy

Grey_Area

For your next zoological love-post may I humbly suggest the tardigrades or "water bears"? They're tiny, cute (sorta), and Freakin' Nigh Invulnerable. No fooling.

Grey_Area

botanicidal

If that were true then the quintessential human superpower would appear to be insanity.

The article itself is interesting, but I fail to see how the adaptation of having the plates again is *reverse* evolution. Moreover I don't really see how there can be *reverse* evolution at all, given what evolution is defined to be.

quetzilla