Discussion of everything related to the Theory of Evolution.
Just wanna tell you in advance that I haven’t majored in biology or any other relevant discipline (so I’m sorry if I say something obviously naive). I have a question to people who are more relevant to this forum though.
This is the link to a set of very peculiar photos
I’ve been kinda puzzled by how camouflage used by creatures in nature has developed through natural selection. Let’s pick this one, for example
This bug, obviously, didn’t develop into a copy of this tree leaf (color, shape, texture, and behavior) overnight. It started as a proto-bug which didn’t look like a leaf at all. If I understand the evolution concept correctly, species evolve over a long period of time through a series of accidental and random genetic mutations from which beneficial ones are retained. For instance, in this video http://www.youtube.com/watch?v=1xNk6w3E6Jg&feature=related Mr. Dawkins gives an interesting illustration of a possible way of an eye development. So, basically, in Dawkins’ example, the eye development starts with a set of simple light sensitive cells which become useful for shades recognition, then a cup develops around them which enhances the process, etc, etc. Correct me if I’m wrong, but the conclusion I drew from the Dawkins’ explanation is that the first retained mutation does serve the purpose even in its simplicity. So the following sequence of mutations in Dawkins’ example only enhanced something that was immediately useful already.
Getting back to the bug… compared to an eye, each individual feature of this bug’s camouflage used alone (either color or shape or texture or behavior) in the stage of its (feature’s) early development seems to have little or none utilitarian use by itself in respect to the tree it’s hiding in. Say if a bug becomes kinda green, but it’s not shaped like the leaf and it crawls all over the branch like crazy, it’s still going to be picked up by birds. If it manages to replicate something that kinda looks like a shape of the leaf, but stays brown in color without alteration of its behavior, it’s still going to be killed…. The point I’m trying to make is that compared to an eye development, each individual feature of the camouflage you see on the picture (color, shape, texture, or behavior) in its early stage of development, doesn’t seem to really serve the purpose of pretending to be an eucalyptus leaf. Unlike in the eye example, I don’t see a gradual enhancement of an immediately useful feature, but rather an application of a set of features which only become useful if they are fully completed and simultaneously applied. The bug must’ve relied heavily on other defensive mechanisms before it developed the look and behavior it has now. If that’s true, wouldn’t the bug loose the features you see on the photo in their rudimentary stages in the process of evolutionary development due to their low immediate / stand-alone utility, before it even had a chance to reach the state of a perfect camouflage you see on the photo?
My previous point can probably be rebuffed (staying just still or just green, does help even without all of these features combined or being fully developed), but the problem is complicated by the fact that, unlike an eye, which is kinda “independently” useful, the bug on the photo mimics a specific type of a tree leaf. So now we have the dependency, the system (bug – specific tree) with multiple degrees of freedom. The tree is a separate being. It is not related to the bug and it chases its own evolutionary goals. So we have a bug which over a LONG period of time managed to develop a near perfect camouflage, which mimics the specific tree leaf which (the leaf) most likely didn’t have its current precise color, shape, and texture at the time when the bug’s evolutionary changes started. Do you see my point? In this case, the “beneficiary” mutation starts before the benefit is even available and somehow overlaps with it almost 100% in exactly the same time and space in the future.
I either have a false logic somewhere or maybe I don’t understand the process of natural selection correctly. Because as it stands, it seems to me that the bug, to be successful, has to undergo a series of really rapid beneficial mutations to be able to mirror a relatively static object (otherwise, if mutations are not rapid enough, the object it’s “trying” to replicate is not going to be static anymore). I do suspect that trees, compared to bugs, are more genetically stable (so the bug’s benchmark might actually be relatively static over a long period of time). But this bug I used is a vivid, but not the only example. An Indonesian mimic octopus ( http://en.wikipedia.org/wiki/Mimic_Octopus )successfully mimics about five different marine animals (in shape, color and behavior). This capacity is definitely not a result of a conscious effort, but rather an instinctive one, developed over a long period of time. But those creatures (venomous snake, lion fish, etc.) the octopus “learned”, over a long period of time, to mimic have also been undergoing genetic evolution, changing color shades, shapes, behaviors, etc…. along the way, most likely with similar speeds as octopus’ mutations . How did the octopus manage to catch up? How does it manage to complete the process before the same natural selection tosses not yet useful rudimentary endeavor into a trashcan due to its low immediate utility or its obsolescence by the time it’s fully developed?
When one grows to a bigger size or develops sharper claws in response to changing environmental demands, this process is not demanding (no one questions why an animal grew its claws 3 inches long or 4 inches long – as long as we correctly understand why it did so at all in response to changing conditions). But this bug or the octopus have to hit their constantly moving future bull’s eyes precisely in all respects (see the picture of that bug again – the resemblance of the eucalyptus leaf is impeccable), or they will fail.
P.S. Unfortunately, I lack time (and knowledge) for frequent replies and discussions, but I will definitely read your feedback (if any). Thanks!
Maybe the missing element here is that bugs exist in populations. Variable populations. Reproductive success is at the heart of evolution, and it is reproductive success relative to the other members of the population that is important. If a bug is slightly greener than all the other bugs, it will have a slightly better chance of surviving and reproducing when spending its time, moving or not, amongst green leaves, thus passing along its slightly more greenishness. Maybe that first slightly greener bug got eaten anyway before reproducing. Fast forward a thousand years. A second slightly greenish bug appears but doesn't get eaten. Slight greenishness is now established in the population. Further mutations may then, over time, improve the greenishness. Later, or concurrently, other variants arise in the population that modify behaviour or body length or morphology that allow those bugs to survive better than others in the population. These new traits then get established in the population.
Co-evolution. Nature contains many examples of plant-plant, animal-animal, animal-plant, parasite-host, etc. associations where, if one changes, the other must follow suit or pay the consequences. The bug in the photo is very well camouflaged now. In earlier times when the tree's leaves may have been broader or greener, or whatever, the bug would have been broader, or greener, or whatever. As one species changes, a second species that eats, lives on, lives in, or mimics the first must change along with it, or find another strategy to survive. Evolution cannot predict the future but only deals with what survives best NOW.
The vast majority of species don't cut the mustard and go extinct. Octopi obviously managed to survive, or they wouldn't be here. How they managed to do so, I don't know. We like to think of nature as harmonious and peaceful, but it is actually quite ruthlessly vicious. Eat and be eaten. Survival of the fittest.
That's OK. It's refreshing to get good questions on this forum. I hope some of this helps.
Just wanted to add to Gavin's response, that no you do not need massive and rapid changes.
The proto- leaf insect even when it does not mimic a leaf exactly will still be that much harder to pick by the predators. But some will be picked, and among the picked one will be the worst at hiding. In the enxt generation, there will be again more variations (probably in both directions: easier and harder to pick), and again the most likely to reproduce are going to be the better camouflaged.
You can have fun with this simulation if you want:
http://www.explorelearning.com/index.cf ... urceID=554
Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)
2 Gavin & canalon
Thank you for your replies!
I kinda understand what you’re saying and at the same time it doesn’t stick… I mean logically.
Let me come back to an eye example. The purpose of an eye is a detection (and getting use) of sunlight. It’s a 1-dimensional problem. The benefit has been steadily available to us ALWAYS (the sun has been rising for several billion years). HOW the organism solves the problem – doesn’t matter (the eye of a human being is absolutely structurally different from an eye of a spider). What matters is, again, that the benefit is always there, which means that one has a sufficient time to develop the light-detecting organ, with increasing complexity, but still with a 1-dimensional goal to achieve.
Back to the camouflage… 1) If I ask you to make a detailed description of ALL the eucalyptus leaf characteristics, it will result in quite a list. So we already have a multi-dimensional problem, which, unlike the sun, will be in motion, changing in all these multiple dimensions…. (canalon, without rapid changes, how do you create a carbon copy of something that is also constantly changing?)
2) Lets look at the greenishness… Beneficial mutations are indeed retained. Extra greeneshness could’ve spawned a new, better adopted bug, which would still have to rely on something else before the conversion to a full camouflage is complete (we don’t see that many military snipers fully relying on just a greenish outfit acquired in a local Gap store). In this dicey process greeneshness can still fluctuate depending on numerous environmental factors. And we don’t need just A greeneshness, we need THE specific shade of green from a million of variations. Then one has to become shapier. Then appearance of leaf – like vein in the middle of the body, etc, etc, etc., etc, etc… Evolution, as I understand it, is blind. It blindly reacts in response to the need of survival and it tosses something that it has no use for (like Mexican tetra fish lost it’s eyes, when it lost the need for them in a cave environment). Adding an extra leaf – like vein in the middle of the body should not really increase or decrease the competitiveness of the bug that much until the entire process is complete, and the blind evolution could’ve tossed this feature as unnecessary at the moment. Let me say something dumb. If I collect all these bugs, and draw a tiny funny face with neutral colors on all of them, I bet you it will not decrease their chances of survival. Nevertheless, the blind process of nature turned the bug into a specific tree leaf without any impurities, and succeeded in all respects where all the characteristics of the leaf eventually overlapped in the bug at the same time and space. How did the bug manage to succeed on numerous fronts and achieve perfection in this multi-dimensional quest through the blind process? I mean, I understand, that everyone on this forum can describe to me how it happened according to the concept of evolution through natural selection. But when I step aside and think about it, it’s not quite comprehendible. Maybe it’s just me.
My purpose in introducing the population concept was to indicate that survival depends on what else is present for the predators. In a population of a million bugs, an ever-so-slightly greenish bug, will have an ever-so-slightly higher probability of not being eaten. The 999,999 brown bugs will be an ever-so-slightly easier target. This greenish beginning will, over time, slowly increase to the "THE specific shade of green from a million of variations". Once greenishness is in the population, and a range of greenishness appears, those bugs whose greenishness is less detectable by the predators will have a better chance of surviving and reproducing. Statistical probability of survival is the key. Probability ranges between 0 and 1, where 0 is impossible, and 1 is an absolute certainty. A probability of survival of 0.001 is better than 0.
Bugs tend to be bilaterally symmetrical (the left side is a mirror image of the right side) and have a distinguishable midline on at least the abdomen (the hindmost part). As with greenishness, any mutation that makes the midline look a bit like a leaf's central vein will impart a survival advantage over those bugs that do not possess this feature. How all of this may have happened, I have no idea. Green first, shape next? Shape first, green next? Both at the same time? Generation time is also a factor. Bugs have short generation times compared to us, For argument purposes, let's say that this bug has one generation a year. In a million years, there will be a million generations. That's a lot. And in a population of a million bugs, that's a lot of variation for natural selection to act upon. Things don't have to appear fully formed immediately. ANY slight advantage is still an advantage.
Let's say birds eat these bugs. Birds are very good at identifying prey. If birds learn - and they are good learners - to associate tiny funny faces with a good meal, they will look for, and find, funny faces.
Very slowly. Step by small step. All the intermediate forms must have some advantage, however slight, over the other individuals of the population, even if not "fully formed". Not all of these intermediate bugs will survive to reproduce. But STATISTICALLY in the population of a million bugs, the intermediates are more likely to survive. In time, their progeny will be better intermediate forms, and their progeny will be even better, until we get something that looks like what is in the photo. Evolution is usually very slow and incremental (things, though, can change quite quickly under extraordinary conditions).
No, it's not. We humans have a very difficult time being able to fully grasp the vastness of time. Lots of variation in lots of time can produce lots of things. Now, let me tell you a little about quantum mechanics ...
Gavin, thanks for the reply! I’m familiar with the “peppered moth” argument and I stated in my first post that acquisition of even a few features of camouflage does indeed most likely increase the chances of survival ….
I’m afraid that I’m gonna walk around in circles, but I’ll try…. I do realize that we live in an ever-changing world, and creatures do manage to adopt. But once you develop something, you develop this for a long use. Why? Because as you said, complex structures usually take a very long time to develop. Change is bad. Change destroys the utility of the features we’ve been developing for so long. Lucky us, we still have eyes, cause the sun always shines. We still have hands, cause there is always something available to pick up. Dolphins are slick and mobile, cause oceans are always there providing them with the benefit of being slick and mobile, etc., etc… It’s a linear relationship eyes – light, hands – picking up, and the benefit is always there (or you loose it if you don’t use it)
If I release this bug into an isolated car junkyard, it may even assume a shape of Volkswagen Jetta, that’s possible… after a gadzillion # of years…. provided that we are dealing with the model with 1 degree of freedom (only the bug is allowed to alter its numerous qualities). What if I introduce oxygen and water vapor into the model and Volkswagen Jetta starts alterations of its own. A bug develops a white color, but Jetta turns white with brownish spots. A bug develops wings which look like back view mirrors, but actual back view mirrors develop cracks…. As far as the eyes go, the sun still shines, and the eyes are fine. But as far as development of camouflage goes - we have more than 1 degree of freedom now, so every time a bug develops something in this respect, it’s racing against time. It has to either outpace Jetta in its numerous (colors, shapes, smells, etc, etc) changes or its efforts to mimic will constantly become obsolete. That’s why I said in my first post that the bug has to be a way more genetically active than the tree. And that’s why I used another example (actually there are so many), like an Indonesian mimic octopus (now that system has numerous degrees of freedom) since the octopus has to constantly catch up with a bunch of other animals who are most likely are not that genetically static like a tree.
That was my biggest dilemma. I did not really question the benefit of beneficial genetic alterations. In case of a camouflage, I questioned the possibility of the perfect outcome through slow and lengthy genetic alterations of multiple camouflage characteristics in a constantly changing system with numerous degrees of freedom.
I can see water, I can touch water, I can drink water, but I will never see a perfect reflection of my face on it if it constantly has ripples.
Why couldn't multiple camouflage characteristics develop if they all independently increased the likelihood of survival? A slight greenishness would be an adaptation to avoid predation by birds. A slight elongation of the body would be an adaptation to avoid predation by birds. A line along the midline of the abdomen would be an adaptation to avoid predation by birds. The survival of organisms depends on the environments in which they live in the present. If the environment changes in a way that negatively impacts an organism's survival, the organism will have to adapt to the new environment or pay the consequences (extinction). Let's take the bug in the photo as an example. Imagine that the climate begins to change so that the species of tree to which the bug is so well adapted no longer grows very well, and the tree's population begins to decline. This will have consequences for the bug population. As the trees decrease in numbers, the bugs will decrease in numbers, as will the birds, as will the parasites that live in the gut of the birds. If the variations within the bug population cannot lead to adaptations to the new environment, the bugs will die out. A bug that looks very much like a eucalyptus leaf will not do well in a savannah. But savannahs have leaves too. Perhaps variations in the bug population could lead to even longer or thinner bodies and a different shade of green. Then they would resemble grass leaves.
The history of life on Earth contains periods known as mass extinctions, when changes in the global environments have been so severe or so rapid that a large percentage of all the species present on the planet at the time were unable to adapt, and they died out. No species evolves in isolation. All are parts of ecosystems and environments that can change. The evolution of each component species will depend on the evolution of other species that share the same ecosystem or environment at the same time.
Mass extinctions do not happen every day, and they only confirm that creatures take a long time to adopt. You keep asking why couldn't multiple camouflage characteristics develop if they all independently increased the likelihood of survival? Of course they could, they would and they did. The question is HOW? And I don’t expect any DNA drawings. I raised this question on a conceptual level and I keep repeating it and rephrasing it for better understanding what I’m trying to ask. How did a mimic octopus slowly develop the capacity to mimic qualities of 5 different creatures, which were most likely changing those qualities over the same period of time for the same adaptation reasons? Wouldn’t it constantly fall behind? Or does the octopus’ genetic mutations go faster than those of other creatures? I don’t have problems with adaptations through genetic mutations. I have a problem with those genetic mutations managing to catch up with genetic mutations of other creatures. Yes, it does happen. An airplane does happen to fly, but until someone explains how Bernoulli's principle functions (at least in principal), it still looks like a flying piece of metal.
P.S. Yes, interrelations of species exist left and right - kill all the sparrows, and the bugs will spread everywhere. Development of camouflage is kinda more twisted kind of interrelation.
Probably by a slow selection for better and better mimicry AT THE SAME TIME that the mimicked species exist. As the mimicked species change, so do the octopi AT THE SAME TIME. Also, mimicry does not need to be perfect to provide a selective advantage. If the octopus can imperfectly mimic one species, and that species changes a little, then the octopus will probably still be able to mimic it. If the mimicked creature changes a lot, the octopus could also change a lot. I had a look at a YouTube video of the mimic octopus here:
The degree of mimicry is pretty low.
Maybe the word "slowly" is causing confusion, since you've underlined it. My use of the word is to indicate that evolution usually happens by small, incremental, cumulative steps. Large jumps are not the norm. If the mimic species is changing by large jumps, then it should be disqualified for cheating.
How can it fall behind if the species the octopus is mimicking is no longer around? The octopus cannot mimic something that doesn't exist. Selection occurs IN REAL TIME. There is no looking forward or falling behind. I can't really imagine that a mimicked species could change so much and so quickly that the octopus wouldn't be able to keep pace. And considering the degree of mimicry involved, I don't think the octopus need worry too much. But supposing the mimicked species does change phenomenally extensively and quickly (which would indicate extraordinary environmental changes that may provide the octopus with larger challenges than mimicry), then I imagine the octopus would no longer mimic it, because no selective advantage would exist.
If the octopus can mimic one species, it should be able to mimic two, or five. If I am still misunderstanding what you are trying to ask, then maybe someone else can chime in and take over.
Gavin, I picked the octopus because of the number of different creatures it simulates (the degree of mimicry can not probably go any higher without actual body alteration and then it would be impossible to copy 5 different creatures at the same time).
The last argument you made is very persuading, but when I think about the entire process from the beginning to the end, it’s still looks very unrealistic. The genes mutate through the toss of dice. Yes, the process will eventually lead to retention of only useful features. But each toss of dice in this respect is still absolutely statistically independent from previous outcomes. The fact that the bug is now greener, insures higher chance of survival of it’s kind, but doesn’t seem to increase the speed of even higher greeneshness development (for that particular reason – each consecutive alteration of genes is statistically independent from previous outcomes… am I wrong?). That means that the increased “greeneshness” you were talking about can take quite a time to reach it’s final objective – the bug can keep hitting numerous colors before it hits the shade of green it has today. That’s why I used an eye as an example, cause even the development of an eye seems to be a simpler “assignment” to me – as long as the better capture of light is achieved, the next step is accomplished. The bug can develop absolutely different structural types of eyes, they will still do the job. But there can be only one copy of a leaf at the end – meaning a huge number of trials and errors. That’s on the top of the fact that the object it’s mimicking is constantly changing - winning a lottery on a lottery on a lottery on a lottery… isn't it?
Okay, I'll give it one last try.
Yes (you are wrong). Selective steps are cumulative. Greenishness, once it appears, does not have to be re-invented in each generation. That first bug that stumbled upon a slight greenishness will have a statistically slightly higher chance of not getting eaten. If it survives, it will pass its traits on to the next generation. Modification with descent, as Darwin put it. Its progeny will also have the same statistically slightly higher chance of not getting eaten. So we started with one bug with slight greenishness in the population. The next generation will have ten or a hundred (I don't know how many eggs a female may lay in one generation, but in insects, it's usually quite a few) slightly greenish bugs in the population. You can see that slight greenishness is spreading through the population - increasing in frequency. The greenish bugs will survive better that their brown relatives, reproduce better, and eventually will become dominant in the population of bugs. Now another role of the dice will produce a silghtly even-more-greenish bug, which will have an even slightly higher survival advantage over its merely slightly greenish, and definitely its brown, relatives in the population. Increased greenishness does not occur through a new role of the dice that turns a brown bug into a greener bug. The "alteration of genes" builds on what has already occurred - there's no resetting back to a default level. Once started, the improvement of any trait that will increase survival and reproduction, RELATIVE TO OTHER MEMBERS OF THE BUG POPULATION that are all competing for not getting eaten, will ratchet through successive generations towards perfection, which nothing ever actually reaches. Survival of the fittest (greenest).
Another factor, which will not apply to all examples of camouflage or mimicry, is the relative abilities of populations to change. With the bug example, we have three relevant populations - the bugs, the trees, and the birds that eat the bugs. The ability of a population to change depends on the amount of genetic variation within the population. The amount of genetic variation within a population is highly dependent on the size of the population - more individuals, more mutations (in the population). Each tree will likely have more than one bug on it, so the bug population will likely be larger than the tree population. The bug population will generate more random mutations than the trees upon which natural selection can act. There will also probably be more than one bug per bird. Another factor will be generation time. Trees tend not to start producing seeds until many years after their lives begin. Bugs will have at least one generation per year. The spread of any selective advantage can thus potentially occur faster in bugs than in trees. So, more mutations and faster spread gives the bugs an advantage, in this example.
It might be better to think of it as a lottery within a lottery within a lottery within a lottery, with the probability of winning increasing each time you play.
I don't know if it will help, but you could have a look at:
It's a bit simplistic, since it's meant for kids, and it's nearly an hour long, but it deals with the cumulative aspect of selection. It's the complete lecture from which your initial link is taken.
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