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And so we shouldn't, since evolution doesn't work like that. It can't go 'backward', and neither does the environmental niche in which life finds itself. Yes, the temperature changes, but there are more things than just climate that affect a species' evolution.
Consider the extinction of the dinosaurs: after the catastrophy calmed down, the Earth was back to how it was. But dinosaurs didn't re-evolve: their successors took their place in the niche they left behind.
Events of mass extinction is a different story. The theory of evolution does not work well there either.
Most of the time in the earth history, environment changed in a very mild level; changed very gradually; and changed back and forth. Exactly because what you said that an environment (niche) includes many conditions, it is a strong argument that no life should evolve dramatically over time due to the multiple environmental control.
If evolution were true, life forms on the earth today should still be similar to that at the middle Proterozoic time. The Cambrian explosion (an example of dramatic change) should never take place.
The first question is: why not evolved back to what they were? What would stop it? I don't see a single reason not to do that. I know they don't. But this poses a big question to the mechanism of evolution.
Nothing would stop it except for the fact that it is extremely unlikely that the same mutations that got our little muskratty animals into the pond in the first place will occur again. The occurence of mutation is random. Animals live or die depending on their fitness for the environmental niche in which they live, eat and reproduce. When the climate warms again (in our imaginary case), these critters could become water critters again, but it's astronomically unlikely the same sequence of mutations that put them in the water the first time would happen a second time, because of the random factor.
I don't see how this is a problem for evolution - this is predictable and common sense.
Second, let's assume it does not go back to the same animal before. But it will evolve to something new, BUT, with equivalent functions. I don't see any reason that it will evolve into a very different "kind" of animal.
Our imaginary animal has already evolved into a different kind of animal by the time of the climate rewarming. It has no instinct to go fishing in ponds. It has become an animal that eats insects, perhaps, and the kind of mutation that might cause it to have more successful offspring will more likely be something that makes it better at catching lots of insects - maybe a longer tongue to get into termite tunnels, or thicker claws to dig the termites out. Over many, many generations, its descendents may come to look a little like anteaters, or a badgers.
The main point is: there are only a few ways that environment can change. Under this major control, lives may evolve to here and to there, but they should not do any runaway type of evolution and brought out monsters like the big dinos. The type of mutant described in movies just do not happen.
There are in fact a multitude of ways in which environment can change, especially from the point of view of the living things that inhabit it. Just because the climate becomes warmer doesn't mean everything reverts to what it was like the last time the climate was warm. The plants will be different. The other animals will be different. Where there were prairies, there may be forests. Where there were freshwater lakes there may be peat bogs. It may be wetter or more dry. Some kinds of food will be scarce, another kind abundant. And so on.
There was no 'runaway' evolution to produce the dinosaurs, just evolution as it always works. You must try to grasp the length of time involved, millions and millions of years. Better, think of it in terms of generations of animals, millions of generations of animals having babies that grow up and have more babies. Also, though people emphasize the sheer size of some dinosaurs, keep in mind that the majority of dinosaurs were not unusually large. The blue whale which is still living in our oceans is still the largest animal that ever lived. Is the blue whale an example of 'runaway evolution producing a monster'?
And movies distort reality. Read more, watch fewer movies.
The first question is: why not evolved back to what they were? What would stop it? I don't see a single reason not to do that. I know they don't. But this poses a big question to the mechanism of evolution.
I told you why in my post. Evolution is guided by three mechanics: natural selection, random mutation and genetic drift. Combined, these three will drive evolution in a changing environment, and the entire process is non-random. However, the random element of random mutation will ensure that there will be no "going back".
Think of it this way (warning: overly simplified example): We see a population of hypotheticus exampliensis, a mammal living in lush grassland terrrain, living off of termites. They have a long snout for sucking up termites, heavy claws for burrowing in dirt, short fur and big paws to combat the noon sun and good vision to detect their minute prey.
Disaster! A sudden but small change in temperature forces the termites from the region, southwards towards warmer climate. The food supply is gone. A random mutation has left a small part of the hypotheticus population able to break down the poison of the fly poisonus alternativis, meaning that those hypotheticus able to eat the toxic fly can switch their staple food, and thus survive in the new environment. This mutation is selected for rapidly, and the hypotheticus without the mutation are forced to migrate soutwards, following the termites.
Over the generations, the hypotheticus of the north evolves to be better at capturing and digesting their new food. Beneficial mutations are selected for, the snout becomes shorter and growing more whiskers, the claws disappear and are replaced by paws resembling furry nets. A new spieces is born, from now on called mutatis hypotiensis.
Suddenly there is a new change in temperature. The termites return, and so does the hypotheticus. During it's time in the south, it too has evolved, growing bigger to better combat the abundant predators of the south. Meanwhile, the mutatis has grow furrier due to the cold climate of the north.
A new spieces of spider, monstrous octopedis, has invaded the plains of the mutatis, and the supply of flies are dwindling, as the spiders are eating them all.
Natural selection now takes over again. Mutatis will evolve or it will go extinct. What will happen? Will they revert back to the original hypotheticus form? No, that niche is taken by the current hypotheticus: the termite-eater. Will it die out? Possibly. The food supply isn't enough for both the spider and the mutatis, so something's gotta give. Most probably, the mutatis will either evolve into a new niche: perhaps there's a form of earthworm that is thriving in the hotter climate? It might evolve to become smaller, thus managing to get by on a lesser share of the fly-population. It might evolve to eat the spiders. The only thing it won't evolve to is the same hypotheticus as we started off with. For one, that niche is full. Secondly, the genetic composition of the mutatis has drifted too far from the original hypotheticus, and the odds for it changing back to the exact same genetic composition are astronomical.
There is no "degression" in evolution, as there is no "direction" in evolution. There is simply adaptation.
Originally Posted by juvenissun
Second, let's assume it does not go back to the same animal before. But it will evolve to something new, BUT, with equivalent functions. I don't see any reason that it will evolve into a very different "kind" of animal.
Define "kind".
Originally Posted by juvenissun
The main point is: there are only a few ways that environment can change. Under this major control, lives may evolve to here and to there, but they should not do any runaway type of evolution and brought out monsters like the big dinos. The type of mutant described in movies just do not happen.
No, the type of mutants described in movies just do not happen, you are absolutely right. However, I am sad that you get your education on evolution from movies. How about reading a book and find out how it really works?
[quote=juvenissun;52230857]Events of mass extinction is a different story. The theory of evolution does not work well there either.
Most of the time in the earth history, environment changed in a very mild level; changed very gradually; and changed back and forth. Exactly because what you said that an environment (niche) includes many conditions, it is a strong argument that no life should evolve dramatically over time due to the multiple environmental control.
If evolution were true, life forms on the earth today should still be similar to that at the middle Proterozoic time. The Cambrian explosion (an example of dramatic change) should never take place.[quote
You know Juv, just because your imagination / your knowledge dont let you understsand something doesnt make it so or not so. Your ideas about how the ToE does or does not work well dont mean much, since you dont undrestand it. Its not enough to claim that you understand it. You have to demonstrate; you constantly demonstrate that you dont know.
You leave out a lot of things from your calculation. It makes no sense to say that if the environment didnt change, that evolution wont take place. Just because an organism can survive does not mean that the environment it lives in is optimum for it.
Or that it could not be better adapted. Stability in environments varies tremendously.
The shade one into another. Organisms move about, Your idea is simplistic in the extreme.
Try this. If evolution WERE NOT true, then why is there a distinct sequence of life forms found in the fossil record? Why do we see that life forms changed over time?
Last edited by Hespera; 1st July 2009 at 10:20 AM.
Events of mass extinction is a different story. The theory of evolution does not work well there either.
Most of the time in the earth history, environment changed in a very mild level; changed very gradually; and changed back and forth. Exactly because what you said that an environment (niche) includes many conditions, it is a strong argument that no life should evolve dramatically over time due to the multiple environmental control.
My point was that the environment doesn't change back and forth: it is constantly changing. The precise combination of temperature, salinity, soil type, foliage type, latitude, etc, is never the same. An extinction event would leave environmental niches empty, and so surviving species could evolve to fill them (before, there were already species in them). The existence of this new species changes the environment: a new type of tree, for instance, would change the soil composition, thereby affecting the entire area.
Originally Posted by juvenissun
If evolution were true, life forms on the earth today should still be similar to that at the middle Proterozoic time. The Cambrian explosion (an example of dramatic change) should never take place.
The Cambrian explosion wasn't dramatic: it took place over about 80 million years. It seems dramatic because it represents a mass fossilisation event (a landside, perhaps), and occurred around the dawn of 'hard' bodies: the 'soft' bodied animals that went before were much less likely to fossilise. Not that fossils tend to be shells and bone; before the Cambrian, those were in short supply. Wikipedia has a more extensive explanation on why the diversity of life rose sharply around that time.
__________________
A scientific man ought to have no wishes, no affections, -- a mere heart of stone.
- Charles Darwin
"I am a scientist... when I find evidence that my theories are wrong, it is as exciting as if the evidence proved them right."
- Stargate: SG1
What can be asserted without reason, can be denied without reason.
- Anon
"A casual stroll through the lunatic asylum shows that faith does not prove anything."
Nothing would stop it except for the fact that it is extremely unlikely that the same mutations that got our little muskratty animals into the pond in the first place will occur again. The occurence of mutation is random. Animals live or die depending on their fitness for the environmental niche in which they live, eat and reproduce. When the climate warms again (in our imaginary case), these critters could become water critters again, but it's astronomically unlikely the same sequence of mutations that put them in the water the first time would happen a second time, because of the random factor.
I don't see how this is a problem for evolution - this is predictable and common sense.
Our imaginary animal has already evolved into a different kind of animal by the time of the climate rewarming. It has no instinct to go fishing in ponds. It has become an animal that eats insects, perhaps, and the kind of mutation that might cause it to have more successful offspring will more likely be something that makes it better at catching lots of insects - maybe a longer tongue to get into termite tunnels, or thicker claws to dig the termites out. Over many, many generations, its descendents may come to look a little like anteaters, or a badgers.
There are in fact a multitude of ways in which environment can change, especially from the point of view of the living things that inhabit it. Just because the climate becomes warmer doesn't mean everything reverts to what it was like the last time the climate was warm. The plants will be different. The other animals will be different. Where there were prairies, there may be forests. Where there were freshwater lakes there may be peat bogs. It may be wetter or more dry. Some kinds of food will be scarce, another kind abundant. And so on.
There was no 'runaway' evolution to produce the dinosaurs, just evolution as it always works. You must try to grasp the length of time involved, millions and millions of years. Better, think of it in terms of generations of animals, millions of generations of animals having babies that grow up and have more babies. Also, though people emphasize the sheer size of some dinosaurs, keep in mind that the majority of dinosaurs were not unusually large. The blue whale which is still living in our oceans is still the largest animal that ever lived. Is the blue whale an example of 'runaway evolution producing a monster'?
And movies distort reality. Read more, watch fewer movies.
Exactly. Animals evolved from this to that through time. But why would it make dramatic changes, even given a long time period? For example, changed from water to land and from small to huge? That kind of change is OBVIOUSLY directed. One could not wonder around in a city, but ended up in another continent.
Mutation does not repeat (smallest chance), fine. But a mutation which fits to a backward changing environment should have the character of backward change, even it is a different change. We do not see that at all. What we see are many many forward, dramatic, runaway changes. And most of them did not take that much time to happen.
Exactly. Animals evolved from this to that through time. But why would it make dramatic changes, even given a long time period? For example, changed from water to land and from small to huge? That kind of change is OBVIOUSLY directed. One could not wonder around in a city, but ended up in another continent.
It would create dramatic changes because of natural selection, genetic drift and random mutation. You cannot discount two thirds of the mechanics driving evolution. Furthermore, nature is all about niches. A niche soon gets filled, leading to a species having to adapt to a new environment, a new place in the food change and a new food supply. Given millions of years, this will lead to what you call "dramatic changes".
Originally Posted by juvenissun
Mutation does not repeat (smallest chance), fine. But a mutation which fits to a backward changing environment should have the character of backward change, even it is a different change. We do not see that at all. What we see are many many forward, dramatic, runaway changes. And most of them did not take that much time to happen.
Have you ever heard of whales? A whale is a mammal living in the water. The evolution of whales might be interesting to you, as it completely destroys this part of your argument.
Exactly. Animals evolved from this to that through time. But why would it make dramatic changes, even given a long time period? For example, changed from water to land and from small to huge?
There are very good reasons for that. The water-to-land change occurred because land provided a completely new environment, one filled with resources, food, and territory, and completely devoid of predators and competition.
There was also the growing trend for organisms to live in shallower and shallower water.
Generally, large morphological changes happen because a new environmental niche has become available. That's the point of punctuated equilibrium: organisms remain roughly the same for long periods of time, and only with the advent of new terrain do they rapidly change.
Obviously, biochemical evolution occurs all the time; the arms race against infection is a constant war. But macroscopic, morphological change is rare, but when it happens, it's rapid: pretty much ever novel mutation that was previously detrimental was now fantastically beneficial.
Originally Posted by juvenissun
That kind of change is OBVIOUSLY directed.
Why is it obvious? The mechanism for how and why it occurs is very well understood.
Originally Posted by juvenissun
One could not wonder around in a city, but ended up in another continent.
You could if you wandered south of Texas .
Mutation does not repeat (smallest chance), fine. But a mutation which fits to a backward changing environment should have the character of backward change, even it is a different change.[/quote]
Why? Mutations work by adapting to their current environment. Since we never see a backward-changing environment, and since mutations don't work in reverse, we don't see 'de-evolution'.
Originally Posted by juvenissun
We do not see that at all. What we see are many many forward, dramatic, runaway changes. And most of them did not take that much time to happen.
They took millions of years, juvenissun. Don't get confused by the 'if the history of the Earth was a 24-hour clock...' analogy.
__________________
A scientific man ought to have no wishes, no affections, -- a mere heart of stone.
- Charles Darwin
"I am a scientist... when I find evidence that my theories are wrong, it is as exciting as if the evidence proved them right."
- Stargate: SG1
What can be asserted without reason, can be denied without reason.
- Anon
"A casual stroll through the lunatic asylum shows that faith does not prove anything."
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