io9
Lake Washington, the largest lake in the Seattle area, has long been home to a soft-skinned fish called the threespine stickleback. But over the past fifty years, the lake's population of sticklebacks has changed dramatically: today, most of the fish sport partial or full body armor, a throwback to their origins as saltwater fish covered in bony plates. (In the picture here, you can see an armored stickleback on top, with plates in red; a non-armored one is on the bottom.) What caused the rapid shift in the fish's morphology? It sounds bizarre, but the mutation is the result of pollution being cleaned up in Lake Washington. A program started in the late 1960s to clear the lake of toxic sludge made the sticklebacks de-evolve.
A study in 2005 at Stanford showed that there is only one gene that controls whether a sticklefish will develop bony plates on its body. So clearly this gene got switched on after the lake was cleaned up. But why? According to PhysOrg:
Back when the lake was polluted, the transparency of its water was low, affording a range of vision only about 30 inches deep. The tainted, mucky water provided the sticklebacks with an opaque blanket of security against predators such as cutthroat trout, and so the fish needed little bony armor to keep them from being eaten by the trout.So wait, does that mean I just have to go someplace ultra-clean in order to activate my X gene and get wings and magic powers?In 1968, after the cleanup was complete, the lake's transparency reached a depth of 10 feet. Today, the water's clarity approaches 25 feet. Lacking the cover of darkness they once enjoyed, over the past 40 years about half of Lake Washington sticklebacks have evolved to become fully armored, with bony plates protecting their bodies from head to tail. For example, in the late '60s, only 6 percent of sticklebacks in Lake Washington were completely plated. Today, 49 percent are fully plated and 35 percent are partially plated, with about half of their bodies shielded in bony armor. This rapid, dramatic adaptation is actually an example of evolution in reverse, because the normal evolutionary tendency for freshwater sticklebacks runs toward less armor plating, not more.
"We propose that the most likely cause of this reverse evolution in the sticklebacks is from the higher levels of trout predation after the sudden increase in water transparency," said Peichel, whose Hutchinson Center lab has established the stickleback as a new model for studying complex genetic traits. By examining multifaceted traits in the fish, such as body type and behavior, Peichel and colleagues shed light on the genetic networks at play in other complex traits, such as cancer and other common human diseases.
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.
"Having a lot of genetic variation in the population means that if the environment changes, there may be some gene variant that does better in that new environment than in the previous one, and so nature selects for it. Genetic variation increases the chance of overall survival of the species," she said.
Comments
"So wait, does that mean I just have to go someplace ultra-clean in order to activate my X gene and get wings and magic powers?"
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:
agreed - the term "reverse" evolution is a misnomer, and should be deleted from any discussion of evolution. Evolution is always an adaption to environmental cues/conditions - which is in this case, cleaner water.
Sticklebacks and nudibranchs in one day, squee! My dad had a tank of these in the lab when I was just a small fry. I'm pretty sure they must have come from a population living in swift clear water because they had a lot of plating. It was fun to watch their mating antics, fiesty li'l guys.
"So wait, does that mean I just have to go someplace ultra-clean in order to activate my X gene and get wings and magic powers? " Annalee, you know the drill--if you want (or more "realistically", your offspring) ginchy new mutant powers you have to be in a threat-filled enviroment with tons of lightning-spewing predators or evil telepathic cacti.
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.
@quetzilla: Got a point there. This may be an atavistic trait being turned back on but evolution ain't reversing, it's just going along with whatever helps to survive as the enviroment changes.
If we lockyou up in a perfectly clean room, I wouldn't be surprised if after a time you too devolve... mentally anyway.
(padding of said room optional)
The anti-evolution crowd will argue that they are still sticklebacks though. There hasn't been an observed change to the point of where they are no longer biologically compatible with the non-plated variety. Therefore evolution is false, Jesus is lord and Darwin was a poopy head.
Not that I believe that, I'm just putting it out there.
@Dillenger69: That's just a problem with the nature of words. They'll be sticklebacks until enough people decide to call them something else. Has nothing to do with what they actually are.
Gene switching on? More likely changes in the frequency of the armor gene within a population over time due to natural selection = more individuals with armor.
However, Annalee, if you get it on with Mr. Wings-and-magic-powers, maybe some of your children will be more fit.
I swam in Lake Washington as a child. How soon should I expect the body armor to grow in?
I agree that De-evolution is the wrong thing to call it. But still a cool story.
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.
You guys are all being reverse-racist against de-evolution!
I would have to say that this is as about as close to reverse evolution as one can expect to get...
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...
@quetzilla: I belive the term comes from the common misconception that evolution is goal oriented. Seriously, io9? I'd expect more from a science fiction blog.
@DocGratis:
@ceriphim:
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.
Rubbish! Everyone knows that evolution has been outlawed.
These fish clearly must be destroyed to preserve the natural order.
All afternoon I've been thinking of these little fish in their best shiny red armor and plastic wedding-cake hats swimming about singing, "We are Devo! Dee. Eee. Vee. Oh!"
@botanicidal: Totally agree. I think the reason these researchers used the term was because the fish had reverted to an earlier form of their species. They didn't mutate into a new form, but went back to an old one. But yes, it was an adaptation and therefore evolution.
Holy crap. I've been wondering why Paleo-Christian Medievalism is on the rise...
If anything is happening, they are re-evolving. The adaptations that once protected them are being selected for again, and they are "re-evolving" the plating.
Initially, when visibility dropped, they lost the adaptations that protected them- which is closer to what could be called de-evolution than what is happening now.
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."
@Grey_Area: I think I just fell in love with you...!
Hate to be a band-wagon jumped about the reverse-evolution thing, but I'm gonna.
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.
Um, at the risk of being a little parochial: WE DID IT! WHOOOOOH!! OUR FISH ARE MORE ARMORED THAN YOUR FISH!
Now if I could just get my cat to evolve armor.
I think the most interesting aspect to take away from this story is the fact that our efforts to go "green" may actually be a cause of harm to some species rather than the panacea it's made out to be.
Certainly those efforts must come in the wake of careful consideration.
This is not DE-evolution.
This is simple textbook evolution.
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: The original plates were already the adaptation.
@justhesh: He is correct. This is textbook evolution. Just because they had plate before doesn't mean that getting them again is de-evolution. De-evolution does not exist. The article even states:
"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: I wasn't refuting that.
@quetzilla: @quetzilla: I agree. Evolution is a continuous process. "Reverse evolution" is a non-sequitor, except in that episode of TNG where Worf turns into a funky lizard.
Sure, this is interesting story, and a textbook example of evolution, but this is only half the story! The fish evolved to regain protective plating due to the reduction of pollution in the water, but what about when the water became polluted in the first place?
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!
@marvolvox:
There is no definitive answer, only theories. We can see evidence to support evolution of systems and not de-evolution. We do not see Cro-Magnons or Neanderthals emerging in human populations, stressed for over long periods. Wait…I just thought about that. Okay, so maybe it is de-evolution.
@tyr540: The reason I'm opposed to the term "de-evolution" is simply because it portrays evolution as goal oriented, which it absolutely isn't.
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.
I find it astonishing that such an adaption could be observed in what amounts to a fraction of a tick of the clock in evolutionary terms.
I imagine that Creationists would call this "Divine Intervention". The Stickleback is God's Chosen Fishie.
@SoulCarnival: Right...individual fish did not adapt, but this species of fish, collectively, adapted through the process you described. That difference is what appears to confuse people. The gene got "switched on" (clunky metaphoric language) in the species, not in individual fish.
I love getting to a post late in the game and finding that quetzilla, soul, botanicidal and grey area already made the salient points.
"De-evolve" is a null word. It, and the three Star Trek episodes that use it (Barkley turns into a spider, Quark turns into a hippie, Janeway and Paris turn into newts) should be stricken from the record.
There has been no artificial life created in the lab. So there is something special that has to happen for life to emerge out of non-life. Maybe DNA does allow for a species to adapt faster. Maybe older genes can get expressed if the right stimulus is produced. Survival of the fittest is a good, but population dependant mechanism. There might be other ways to produce quick adaptation.
Why not "re-evolution"? Anyway, fascinating article!!
So, does this explain why I can't find my car keys?
this article is sw-eeee-t!
Perhaps I'm missing something, but isn't this just a result of adaption, driven by the "non armored" variety being eaten more often than the "armored" variety, therefore causing the armored fish to reproduce more and therefore become the mainstream population?
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.
If evolution isn't goal oriented, explain the existence of Salma Hayek.
Sorry... lost my train of thought. Fish?
We don't know that evolution isn't broadly goal oriented. In as much as one can only speculate about the goings-on in the pre-big bang sigularity. Maybe the One Mind said, "Okay, this time around the goal is Me. Evolution will be driven by the goal of super intelligence and that in turn will strive to convert all matter in the universe into a god-like being. It's the ultimate way to reproduce and only takes an average of...well, how old is the universe now?
@Jeff-Minor: he he :)
Fortunately, the point I was trying to make was better made by Goodnightbabytron.
To sum up:
Old fishies -- glowing
New fishies -- extra crunchy
Excuse me? Evolution? I think we all know that Jeebus gave these fishes their armor to prevent them from being smited (smitten?) because they are truly righteous animals. You can even see Him in action in this picture I found.
I was all prepared to make a comment about fish-Superman and fish-Doomsday but all the actual science comments distracted me. Then I started humming about the comments "blinding me with science" and the fish-Superman thought couldn't compete.
Hey, natural selection taking place, right in my brain!
You know, I read that "reverse" thing and I got mad... So I came in here today expecting that like most other internet sites, people posting would have no idea what they were talking about and debating on if this was "reverse evolution" or not.
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.
@ marvolvox & DocGratis: I beg you, and all, not to discount gene expression, that is the turning (switching) on and off of genes regulating the development of organisms - in this case the bony plates on the sticklebacks.
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.
The conservation of genetic capabilities, once they have been incorporated into an organism's genome, is supported by the ability of the genome to switch particlular genes on and off. That capability is not bioenergetically "free" and so itself can be posited as having advantages to the survival of the genome and its host organism.
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 d