Does evolution follow the scientific method? If so, how?

[CharonY]

As a general comment, of course it is not possible to reconstruct the evolutionary history of each and every trait. But that is not what evolutionary science is about. As an analogy particle physics is will not explain where each atom came from.

 

Actual science on the subject (if we go away from hand wavy narratives) it depends a lot on the subject being investigated. Here, you typically look at specific alleles and search whether there are differences from a null model (linkage disequilibrium being an obvious example). Thus traits under some form of positive or negative selection will exhibit different frequency distributions than neutral ones.

 

In simple organisms as bacteria it can be investigated much more directly by applying a stressor that acts as a selective force. "Favorable" as a term is not terribly helpful as it would have to be linked to the selection itself. I.e. instead of stating that you are doing an antibiotics selection you would have to state that you are creating a condition favoring resistant bacteria resulting in a pool with higher frequency of bacteria. I have no clue why one would change well-established linguistic usage for no apparent good reason.

 

Also one difference is "favor" implies something directional or positive. However selection can be positive as well as negative (the latter probably more common in stable situations), resulting often in non-directional (or sometimes disruptive) selection.

Again, the use of selection is much deeper than the discussion actually touches upon (as Ophiolite already implied) and I feel that the whole discussion is prolonged unnecessarily by focusing on some misunderstood concepts. Maybe if you replace the word "selection" with "filter" it would make more sense to you (but it would not follow common usage).

 

It is a bit like discussing why quantum mechanics is not called something else because it is in truth not about mechanics (just to pull something out of thin air).

Edited November 15, 2014 by CharonY

[Dekan]

As a general comment, of course it is not possible to reconstruct the evolutionary history of each and every trait. But that is not what evolutionary science is about. As an analogy particle physics is will not explain where each atom came from.

 

Actual science on the subject (if we go away from hand wavy narratives) it depends a lot on the subject being investigated. Here, you typically look at specific alleles and search whether there are differences from a null model (linkage disequilibrium being an obvious example). Thus traits under some form of positive or negative selection will exhibit different frequency distributions than neutral ones.

 

In simple organisms as bacteria it can be investigated much more directly by applying a stressor that acts as a selective force. "Favorable" as a term is not terribly helpful as it would have to be linked to the selection itself. I.e. instead of stating that you are doing an antibiotics selection you would have to state that you are creating a condition favoring resistant bacteria resulting in a pool with higher frequency of bacteria. I have no clue why one would change well-established linguistic usage for no apparent good reason.

 

Also one difference is "favor" implies something directional or positive. However selection can be positive as well as negative (the latter probably more common in stable situations), resulting often in non-directional (or sometimes disruptive) selection.

Again, the use of selection is much deeper than the discussion actually touches upon (as Ophiolite already implied) and I feel that the whole discussion is prolonged unnecessarily by focusing on some misunderstood concepts. Maybe if you replace the word "selection" with "filter" it would make more sense to you (but it would not follow common usage).

 

It is a bit like discussing why quantum mechanics is not called something else because it is in truth not about mechanics (just to pull something out of thin air).

 

Quantum Mechanics is called "Mechanics", because it works. But nobody understands why it does.

 

This is possibly like "Evolution". Nobody understands why a bacterium should evolve into a human brain.

[delboy]

 

If a trait is anything within the phenotype, then a complex organism is made up of an astronomical number of traits. How in the world can we determine in that crow in the tree which of her traits were selected and which just came along for the ride? was the beak selected? or the beak plus the nerves and muscles that move it? or all that plus the geometry of the skull that supports the beak? or the whole bird?

 

 

I don't quite understand the question, but a crow is a crow because 3.5 billion years and however many billion generations of evolution got it there. Every trait it has, has been selected. That's the beauty and the wonder of it surely, that it's so complex, and that the reason it reached this point is only because of the immense amount of time that it's had to get here.

Selection is like binary, it's either for or against. I think what you're asking is how can one unit of selection work on so many traits. The answer is the number of generations and the number of individuals selected for or against over many years. Eventually the favourable traits (sorry, don't know what else to call them) will spread throughout the population and the less favourable ones will cease to exist. One individual crow with a poorly deformed beak might survive and reproduce (ie be selected) if food is plentiful. But no way is the trait going to survive long term.

[Ten oz]

That's not a criticism, it's a feature. It actually boggles my mind that something so tautologically simple as that isn't understood by some people, although I guess I now see that even understanding this fact doesn't really seem to aid comprehension.

There will be more copies of things that make more copies of themselves. That's how natural selection works. Things that are better at copying themselves will gradually increase in number over time in comparison to things that are not as good at copying themselves. How do you define whether something is good at copying itself? By how many copies it successfully produces.

Throw in variation among all of the copying and this inevitably leads to an accumulation of traits that that make things into better self-copiers, because eventually the majority will always be made up of whatever made the most copies of itself.

This is a good post but I think for some people who are not clear on the process it could be confusing. Things that are good at copying themselves will produce more copies assuming they have an opportunity to do so. Evolution has not favored the successful anymore than it has the lucky. Doesn't matter how good a species is at reproducing if a meteorite blows up it's habitat or a volcano eruption destroys its food source. Many highly adapted seemingly successful species have gone extinct. In some cases mutations allows certian species to survive while in others cases it was the eradication of competitors through random processes. Natural selection does not necessarily favor "good". It simply rewards whatever is actively alive.

[CharonY]

Ten oz, that is a very confused declaration of things, I am afraid.You are conflating various mechanisms into one narrative that is not in agreement with common use or understanding of selection. A distinction between selection and stochastic elements have to be made as the effects on genotype are expected to be different. Moreover, survival of species or of alleles are again different things (selection acts on the latter. In fact extinction cannot typically be explained in the context of natural selection).

 

These are somewhat understandable misunderstandings, but will make a discussion of what selection is quite complicated. Especially the last sentence again conflates various issues as natural selection does no such thing. Whatever is alive is actually subject to selective events that will determine the gene pool of the next generation.

[Ten oz]

Ten oz, that is a very confused declaration of things, I am afraid.You are conflating various mechanisms into one narrative that is not in agreement with common use or understanding of selection. A distinction between selection and stochastic elements have to be made as the effects on genotype are expected to be different. Moreover, survival of species or of alleles are again different things (selection acts on the latter. In fact extinction cannot typically be explained in the context of natural selection).

 

These are somewhat understandable misunderstandings, but will make a discussion of what selection is quite complicated. Especially the last sentence again conflates various issues as natural selection does no such thing. Whatever is alive is actually subject to selective events that will determine the gene pool of the next generation.

I do not neccessarily disagree with any of that. However my point is simply that natural selection does not favor success in terms of bigger, stronger, faster, smarter, etc. It favors repuduction and often throughout history natural events have chosen which species reproduce. Opportunities for reproduction are not always equal.

[CharonY]

 

I do not neccessarily disagree with any of that. However my point is simply that natural selection does not favor success in terms of bigger, stronger, faster, smarter, etc.

 

I agree with that part, but it should be noted that while potentially a misconception, it is probably not the best to bring it up, unless it is obvious that someone else was under these assumptions (and quickly skimming the op it did not appear to be the case). Otherwise it may complicate matters.

I disagree with the latter part as NS doe not favor reproduction. Rather, it is a selective filter that changes the genotype composition. Due to this misconception, I presume, you may confuse stochastic events with selection. Think of it that way, assume there are three alleles in existence (A, B and C). They are essential and fulfill the function with simliair efficiency. Assume now that mutations create more variations, but none of them are functional or have reduced functionality under the given environment. The result is that selective sweeps stabilizes the existing genotypes. All things considered equal, the three will keep a steady frequency in the population.

Now assume that there is a change in environment results in C providing a fitness increase over A and B. Now over time we will see the frequency shift towards C (positive selection). Now assume that there are many more alleles (say A-Z) and none of them provide fitness benefits. However E is detrimental. Now selective sweeps will eliminate E over time (negative selection).

Now contrast each these effects with stochastic effects in which individual members of a population are randomly eliminated (and note that the effects will be heavily affected by population size.).

 

If, on the other hand you mean that different populations in different environments have different reproductive conditions, then I am not sure what you mean as it also trivially means that they face different selective pressures.

Edited November 17, 2014 by CharonY

[Phi for All]

 

Quantum Mechanics is called "Mechanics", because it works. But nobody understands why it does.

 

This is possibly like "Evolution". Nobody understands why a bacterium should evolve into a human brain.

 

Wrong. Wrong. Wrong. And not even wrong.

[Ten oz]

@ CharonY, you are right. It is a point that probably didn't need to be brought into the discussion.

[davidivad]

i always find such arguments only shadow how we see things which is subject to perspective (a very powerful tool).

after all, what can we argue without a point (a matter of human condition).

the truth is that nature works without reason.

does evolution follow the scientific method?

no

it is not an entity but a word used to describe something.

[Robittybob1]

i always find such arguments only shadow how we see things which is subject to perspective (a very powerful tool).

after all, what can we argue without a point (a matter of human condition).

the truth is that nature works without reason.

does evolution follow the scientific method?

no

it is not an entity but a word used to describe something.

Well what is that something?

[Marshalscienceguy]

I am a supporter of evolution, and I often see creationists claiming that evolution is not scientific because it fails to meet the requirements of the scientific method.

 

They claim that any scientific idea must be testable, observable, repeatable and falsifiable, and this is true.

I know that direct observation is not always possible in science, but I want to know, how do scientists test evolution (changes that create new species)? How is it observable?

 

I am not referring to natural selection, like bacteria resistance or changes within the same species, I am referring to those changes above a species level, which create new ones. How do scientists test and confirm speciation? How is speciation a repeatable idea?

 

I am not doubting evolution, it's just because these claims have made me feel consufed.

 

Creationists often claim that there are no transitional fossils in the fossil record. Is it true? I would like tests that confirm speciation (creation of new species) by geographic isolation.

 

I thank for replies!

Well dogs kind of work like Darwin's evolution theory. Dogs were one thing and people started breeding dogs with different abnormalities to get desired traits. This includes size, weight, ear shape, tail shape and length, nose length, body length, bigger head(some to the point they cant reproduce naturally as in bulldogs), So if you wanted to argue this is an example of "Artificial evolution" you might be able to go for that. If you wanted to prove it with some type of experiment.

[Strange]

Well dogs kind of work like Darwin's evolution theory.

 

Exactly like. And it can be argued (and has been) that, say, chihuahuas and great danes should be considered different species because of the reproductive barrier.

[hypervalent_iodine]

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Moderator Note

Some time around page 2 or 3, this thread started going a little too far down a few rabbit holes.

- Starlarvae, you have your own threads to discuss your ideas. Don't hijack others. Shortly after I post this, I will be splitting all of your posts in this thread (and their replies) somewhere else (tbd).

- The rest of this discussion seems to be dominated by overtone trying to tell people who work in or close to evolutionary biology how evolutionary biology works. I will be splitting these posts as well (and locking it pending review), since the conversation has become so focussed on specific points as to be a separate issue to the one(s) the OP wanted to discuss.

Edit: two new threads are found here - http://www.scienceforums.net/topic/86743-stochastic-events-and-natural-selection-split-thread/and http://www.scienceforums.net/topic/86744-starlarvaes-thread-hijack-from-does-evolution-follow-the-scientific-method-if-so-how/

I am closing this thread also, pending review.

[hypervalent_iodine]

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Moderator Note

Update! Thread(s) to remain closed.