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Author Topic: Does Darwin's Evolution Theory explain metamorphosis caterpillar to butterfly?  (Read 27789 times)

Offline nova

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There are some evolutionary changes that we cannot explain, but seem possible.  However, how can one explain that the caterpillar evolved to change into a butterfly when such a quantum change involves giant steps that could not be achieved by our understanding of evolution involves slow, gradual changes?  For example, we would assume that at some point in past history the caterpillar makes itself a cocoon: why make a cocoon?  Once evolved to make a cocoon around itself, how can evolution suddenly skip through thousands of steps at a single point in time in order to come out a butterfly?  I am not a religious person, and I do believe in the theory of evolution, however, it seems to me that the process must include some significant other factors than Darwin';s Evolutionary Theory.  In the example of the caterpillar to butterfly, it's as if there was an external intelligence that might have been involved.

Your feedback would be appreciated     


 

Offline Geezer

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There are probably countless examples of evolution that might lead us to conclude that there was some "intelligent" driving force at work. However, consider that you might be comparing the time scales of evolution processes with time scales of processes that you are familiar with.

Evolution is slow and very subtle. It tends to operate over time periods that we may find difficult to relate to.
 

Offline nova

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There are probably countless examples of evolution that might lead us to conclude that there was some "intelligent" driving force at work. However, consider that you might be comparing the time scales of evolution processes with time scales of processes that you are familiar with.

Evolution is slow and very subtle. It tends to operate over time periods that we may find difficult to relate to.

I understand that evolution is very slow, but metamorphosis does not seem to relate to the small incremental steps that we normally consider when discussing evolution.  There are many biological changes that occur during metamorphosis that do not seem possible under our normal understanding of evolution: many of these changes would result in the necessary death of the insect prior to to the next evolutionary step.

One concern that I have is that we should not assume that the evolutionary theory as we now know it covers everything.  We should not get lazy about the dogma of the theory as we know it and be blinded about such 'miracles' as metamorphosis, assuming that such quantum changes must automatically be under the Darwin umbrella.
Again, is something else at work in conjunction with Darwin's theory?

Can someone explain even crudely how metamorphosis could have evolved without the death of the insect at many points during such a radical biological restructuring?       
 

Offline RD

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A wingless creature developing a tiny bit of a (proto)wing wouldn't gain an advantage from it: a tiny stump couldn't help it fly or glide, so there wouldn't be natural selection for wing development by that incremental method, (as in eye development).

It appears wings have developed by adaptation of an existing useful structure, e.g. limbs or antennae, (or maybe a display structure).
« Last Edit: 22/11/2010 03:42:27 by RD »
 

Offline Bored chemist

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Nova raises a good point and, so far, nobody has answered it. I'm about to fail to answer it too.

I can see how "half an eye" is useful or how a limb might become a wing and I dare say Nova can too.

What's the half-way house for metamorphosis?
 

Offline BenV

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What's the half-way house for metamorphosis?

Moulting?
 

Offline JP

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I understand that evolution is very slow, but metamorphosis does not seem to relate to the small incremental steps that we normally consider when discussing evolution.  There are many biological changes that occur during metamorphosis that do not seem possible under our normal understanding of evolution: many of these changes would result in the necessary death of the insect prior to to the next evolutionary step.       

This may or may not be important here, but Darwin's version of evolution is just the foundation for modern theories of evolution.  Some of it has been modified and built upon to arrive at a modern theory.  Darwin stressed that evolution is very slow, but some modern theories propose that evolution can sometimes happen quickly.  One example I know of is punctuate equilibrium, which proposed that the lack of transitional fossils might be because some evolutionary steps happen quickly:
http://en.wikipedia.org/wiki/Punctuated_equilibrium#Supplemental_modes_of_rapid_evolution

Unfortunately, I don't know enough about evolutionary biology to tell you whether that could answer your question or not, but it's food for thought at least.
 

Offline RD

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There is also atavism to consider which can cause an (ancient) feature appear fully formed, out of the blue : rather than by incremental changes, (although the feature may have first formed by incremental change), e.g. humans born with tails.

The caterpillar could have had a life cycle which did not involve changing into a butterfly,
but it carried ancestral dna of a insect born with wings, which made an atavistic reappearance producing the metamorphosis into a butterfly, i.e. the caterpillar may not have developed wings incrementally, it may have got them all at once, fully formed, via atavism.
« Last Edit: 22/11/2010 11:34:15 by RD »
 

Offline nova

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There is also newbielink:http://en.wikipedia.org/wiki/Atavism [nonactive] to consider which can cause an (ancient) feature appear fully formed, out of the blue : rather than by incremental changes, (although the feature may have first formed by incremental change), e.g. newbielink:http://www.anatomyatlases.org/AnatomicVariants/SkeletalSystem/Images/19.shtml [nonactive].

The caterpillar could have had a life cycle which did not involve changing into a butterfly,
but it carried ancestral dna of a insect born with wings, which made an atavistic reappearance producing the metamorphosis into a butterfly, i.e. the caterpillar may not have developed wings incrementally, it may have got them all at once, fully formed, via atavism.
Atavism seems to me to be a good stab at a reasonable explanation, however, we are still left with the fact that metamorphosis is such an 'all-or-nothing' process.  Atavism on it's own still does not seem to fully answer the question: when one considers the fact that the caterpillars body becomes basically mush in the crysalis, to be dramatically re-arranged, it still does not seem possible that evolution could have proceeded without the death of the insect at some point   
 

Offline Pikaia

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Evolution is a slow process, so metamorphosis would have evolved slowly. The first insects would have had no metamorphosis, then later partial metamorphosis would have evolved, then full metamorphosis. Modern insects show all three levels, which is evidence that it did evolve.

There is considerable advantage in metamorphosis. Adults and young are able to use a different food sources and habitats so they are not in competition, so there could have been plenty of evolutionary pressure to evolve metamorphosis. I don't see why metamorphosis had to be lethal at any point.

If you cannot explain how it evolved it merely demonstrates your lack of imagination, not the impossibility of it evolving!
 

Offline nova

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Evolution is a slow process, so metamorphosis would have evolved slowly. The first insects would have had no metamorphosis, then later partial metamorphosis would have evolved, then full metamorphosis. Modern insects show all three levels, which is evidence that it did evolve.

There is considerable advantage in metamorphosis. Adults and young are able to use a different food sources and habitats so they are not in competition, so there could have been plenty of evolutionary pressure to evolve metamorphosis. I don't see why metamorphosis had to be lethal at any point.

If you cannot explain how it evolved it merely demonstrates your lack of imagination, not the impossibility of it evolving!
I realize that there may be an explanation, and that the fact that I cannot explain how the theory of evolution and metamorphosis are compatible does not mean that it is not so. 

A concern that I have is that if we blindly accept our present theory of evolution because it seems to fit 99% of the changes that we have seen over biological evolution, we may ignore the other 1% that we have no explanatiuon for, and thus the possibility of adding to or modifying the theory.         
 

Offline BenV

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I'm still sticking with moulting as an intermediate mechanism.  New tissues form under a hardened exoskeleton.  It's not an enormous jump for new, different tissues to form, rather than new, bigger tissues as in standard moulting.
 

Offline JP

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A concern that I have is that if we blindly accept our present theory of evolution because it seems to fit 99% of the changes that we have seen over biological evolution, we may ignore the other 1% that we have no explanatiuon for, and thus the possibility of adding to or modifying the theory.        

Fortunately that concern isn't justified.  The theory of evolution has been and will continue to be modified as new evidence comes in.  The basic ideas still follow from Darwin's writings, but the theory has changed since then in order to explain various things his original theory couldn't.  If 1% of traits aren't explained by the current theory, then expect to see scientists working like mad to figure out how to explain them.
 

Offline pootle

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Sorry to jump straight onto this as a newbie, but it got me thinking...
The problem with metamorphosis seems to come from the assumption that the process evolved in the same order that it occurs.
for example, just because the creature becomes a chrysalis then a butterfly, doesn't mean that the chrysalis evolved before the butterfly.
to propose a hypothetical example...
A tadpole becomes a frog without the need for a chrysalis.
The frog continues to evolve, so that the difference between frog and tadpole increases, and the metamorphosis becomes more complicated.
As metamorphosis becomes more complicated, the vulnerability of the organism during the process makes it advantageous for it to be better protected.
The individuals with, for example, tougher skin, (at least during the process)are more likely to survive.
The tougher skin becomes exagerated until it is distinguishable from the rest of the organism.
once the chrysalis has evolved, the extent of the metamorphosis can evolve until it entails a complete decomposition.
Any holes in there?

 

Offline Dasyatis

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I'm going to have to agree with BenV on the moulting mechanism being the precursor to the cocoon.

As for metamorphosis, ontogenetic (i.e. age-related) changes in morphology are quite common in life, as juvenile or larval forms often have a completely different set of evolutionary pressures than adult forms (Big fish eats little fish unless little fish grows up to become a bigger fish),so the evolution of metamorphosis is quite clear. Many insects are hatched sans wings, and eventually develope them as they grow. Organisms that began producing offspring that avoided competition until ready to do so were successful. These changes are often more pronounced in invertebrates and lower vertebrates due to their predominantly (or ancestral) r-selected lifestyles. Advantageous and/or neutral mutations (i.e. adaptations) are commonly conserved (humans get hiccups from frogs) and so while some traits don't necessarily make sense, they have been inherited nonetheless.

Butterflies having a unique life-history is actually better evidence to support their evolution, if you ask me. Cocoons provide excellent protection during a critical and vulnerable growth stage. Why don't I have a cocoon? Oh wait, I did, it was called the womb.
« Last Edit: 20/04/2011 22:44:08 by Dasyatis »
 

Offline CliffordK

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When you think of evolution.

4,000,000,000 years is a very long time, although perhaps of that was dominated by the prokaryotes.

There are many parts of human development that mimic a fruitfly, yet we "metamorphasize" as mentioned in the womb into infant humans.

Perhaps the cocoon can be considered an extension of the egg.

Each organism must find a way to feed its embryo. 

An human egg carries just enough energy for a few divisions, and enough to implant in the uterine wall.  The uterus and placenta then provides the energy to the developing embryo/fetus.

An Ostrich lays a large egg that provides the developing chick with all the energy it requires until it hatches. 

Perhaps the caterpillar is another adaptation for developmental energy.  The tiny egg hatches and a caterpillar emerges, absorbs more energy, then returns to an egg-like state in the cocoon to finalize development.  The cocoon would, of course, become optimized to provide protection during this secondary developmental phase.  Such a split developmental cycle would provide a developmental advantage by providing the developing "embryo" with more energy than would otherwise be possible to store in the egg.

As mentioned, the development of the modern cocoon was likely a gradual adaptation for the longer developmental period required by the modern butterfly.

Wings...

There are many mechanisms that one could imagine that would lead to the evolution of wings.
Certainly the evolutionary pressures exist.  If one is prey, and the predators are on land, then the ability to fly would increase survival. 
If one is a predator, then flying while hunting may be equally beneficial.
And flight increases the ease of spreading to new environments.

Wings might not be too unlike the fins that fish have, or the webbed digits that many aquatic animals have.  Even if webbing is lost in one evolutionary step, it might be able to be regained later.
 
Consider a grasshopper.  Strong powerful legs to hop into the air.  Wings may be a later adaptation to improve transportation.  Initially augmenting the ability to hop.  Potentially later the wings will completely replace the requirement for strong rear legs.  The body could become sleeker, and the wings better developed to reduce energy demands.
 

Offline yor_on

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Nova, I think you're defining it a little tricky in your first post. You say "However, how can one explain that the caterpillar evolved to change into a butterfly when such a quantum change involves giant steps that could not be achieved by our understanding of evolution involves slow, gradual changes?"

That is not the whole truth, all genetic mutations are leaps into the unknown, and even though most are failures some become dominant successes. And that is also a part of evolution.
 

Offline The Penguin

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It seems to me that many insects go from larvae to winged creature. I would suspect that the cocoon came after the original transforamtino was evolved as way to protect that sensitive period in their lives. Metamorphosis is nothing more than the maturing of a baby butterfly. I would also like to note that many chrysalis blend in with the places they are attached to. Like this one that looks like a branch. This is evidently a product of evolution

 
 

Offline Evenoire

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But there is a big problem with what people are saying about moulting as a beginning step for metamorphosis with regards to the butterfly/moth. Unlike say, a tadpole who grows lets and a tail and such, a caterpillar goes through a complete restructuring. Other insects, yes grow and change, but the change a caterpillar goes through is quite different. Absolutely nothing of its original form is remaining. It is not like it starts to kind of sculpt and refine its immature juvenile form. It actually reverts back to essentially a pseudo Embryonic state and grows back up from what are essentially stem cells. The caterpillar actually De-evolves into mush and reconstitutes itself.

Studies performed on the caterpillars have also shown that they are almost whole new beings all together. Unless learned just prior to it undergoing metamorphosis, a butterfly will actually have very little memory of its life as a caterpillar. In a  sense, caterpillars actually live and die twice. This is a very weird and odd evolution. One that doesn't fit the typical mold of change followed by other insects.   
 

Offline cheryl j

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Although butterflies may seem unique, there are lots of organisms that have quite different forms at various life stages. Many parasites, for example have free living and parasitic stages, or different forms in different animal hosts. Fungi also look very different at different stages, or may even take different paths in their development. In a way, I'm not sure why going from caterpillar to butterfly is any more complicated than going from a fertilized age to a human being. To me it just seems like the butterfly's development has been drawn out past the egg stage because the egg could not provide the energy needs to sustain it.
 

Offline creck

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This is a topic that has fascinated me for a long time. I recently reread 'Quantum Evolution - life in the Multiverse', after reading, it occurred to that it was another book about evolution that did not mention metamorphosis in the butterfly's life cycle. Maybe some authors do try to explain but I have not found any with realist suggestions.
I found this thread and read it with interest. I have the following comment.
‘Evolution is slow’  wrote somebody. This is of course very true, but the meaning is surely that it is composed of small steps not just that it took a long time. That each small step must be an ‘improvement’ or at least a survivable alternative is the unavoidable meaning within the Darwinian theory. One alternative is that quantum effects in the ‘Multiverse’ allow several steps to occur as long as they are possible before returning to the classical state. That is, only several changes within one gene causing a jump in characteristics, rather than a small change. This allows several things that are puzzling in the science of evolution still. Maybe the strange life cycles involving metamorphosis are some that could be allowed?
It seems unlikely to me, as the change from without a chrysalis stage to using it; seems rather more than a few small steps!! I don’t understand how a gene can contain the information for two independent lives (it seems). Yet a frog (for example) goes through two very independent life types without going into an amorphous mass as an intermediate stage. Which came first? The frog’s evolutionary life cycle  or the butterfly’s step?
 

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