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Author Topic:   Peppered Moths and Natural Selection
Member (Idle past 1561 days)
Posts: 2965
From: Los Angeles, CA USA
Joined: 08-09-2005

Message 6 of 350 (261596)
11-20-2005 5:42 PM
Reply to: Message 4 by RAZD
11-20-2005 9:24 AM

Misreading Randman
First off, Razd, excellent OP here. Lots of info, very well organized.

I think, however, that people have misunderstood Randman's point.

I don't think that Randman is saying that Peppered moths are not an example of natural selection. I think that he is saying that the texts over simplify or mistate the facts.

To a degree he's right.

Your OP is a great example of how it could read in a text book. You give all the important information, and I suspect that Randman wouldn't object to so much info being in the text.

The problem is that these textbooks don't have the time or space to go into this kind of detail. Especially at a grade school level where the kids likely wouldn't understand the concepts, but even at a college level where what's being taught as a primer on the subject.

While the typically scene peppered moths example works well in a text called "Biology and you", I would think they'd go into more detail in a text called "Advanced Theories of Evolutionary Biology".

As far as I understand it, Randman's point is that we should be teaching the whole story, not misleading pieces of it. I agree on principle, but not as principal. (Wow! I couldn't stop myself from that pun!)

You can still teach a kid history, even though you are telling them that people before Columbus thought the world was flat.

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 Message 4 by RAZD, posted 11-20-2005 9:24 AM RAZD has acknowledged this reply

Member (Idle past 1561 days)
Posts: 2965
From: Los Angeles, CA USA
Joined: 08-09-2005

Message 20 of 350 (261662)
11-20-2005 9:12 PM
Reply to: Message 19 by randman
11-20-2005 9:07 PM

Re: mere unfounded claims
Quicky, since I'm running out the door.

So you consider the fact moths are mainly eaten by bats to be irrevalent? Maybe one type of bat prefers the darker colored moths and another the lightly colored moths, and can distinquish them by their flying patterns, and thus differing bat populations are to explain differences in types of moths found?

If this were the case, it would also be an example of natural selection. An increase in bat population A results in a change in Moth population

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Member (Idle past 1561 days)
Posts: 2965
From: Los Angeles, CA USA
Joined: 08-09-2005

Message 65 of 350 (261793)
11-21-2005 4:06 AM
Reply to: Message 26 by randman
11-20-2005 9:33 PM

Slow down everyone
Once again, we're getting into minutia about the study. I couldn't care less about the study. I want to make this simple, so I'm going to state the facts as I see them.

1) We are all familiar with the common story of the moths, it's in a lot of text books.
2) The events in the study may not be as clear cut as they appear in textbooks. The textbooks often minimize the study to a paragraph written for 6th comprehension. This minimizing necessarily deletes some information which could have a great deal of importance.

Randman is objecting to the study being presented in it's simplistic form. He feels that leaving out the various factors he's proposing makes the study less than scientific. And, in regards to textbooks, he's right.

Others are pointing to additional studies which correct the problems Randman sees in the initial study. I don't have time to go through them all, but I'm willing to accept that when taken as a whole, these studies likely answer most if not all of Randman's questions.

So - could textbooks say more? Yeah. Could Randman devote hours and hours daily to reading every study published on the subject? Yeah. Is either of these things likely to happen - no.

To my mind, there are really just two issues which this topic brings up:

First, is this an effective tool for teaching the theory of natural selection?

I say, yes. Despite the problems Randman is bringing up, this study effectively illustrates to a casual reader/beginning student of the field (be it 5th grade biology or college level bio 101) the mechanics behind natural selection.

Are there other studies which could be used? Sure. Do the other studies convey the concept? Probably. But this is one that's in common use.

Second, and more importantly for our discussion here, assuming that everything about the moth study is completely false, is anyone here (Randman or otherwise) trying to argue that natural selection does not take place?

If Randman isn't arguing against natural selection, I don't understand what all the fuss is about.

His continuing point that text books, even today, often contain misleading or factually wrong information is a solid one. Does a mistake in a textbook negate all other studies of evolution - of course not.

Personally, I think Randman is overlooking the numerous factors involved in writing, editting, publishing, and selling textbooks. If the industry was education driven more than market driven, I think a lot of these concerns would be easier to address.

But, let's not let the wheels fly off the cart. We can have a discussion rather than a shouting match.

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Member (Idle past 1561 days)
Posts: 2965
From: Los Angeles, CA USA
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Message 67 of 350 (261795)
11-21-2005 4:19 AM
Reply to: Message 40 by randman
11-20-2005 10:36 PM

Re: If it is natural selection, what is false about protraying it as natural selectio
The logical fallacy here is to claim demonstrating natural selection alone is demonstrating evolution

I don't think that that's what he's trying to do. Or, more accurately, I don't think he should be trying to that if he is.

You may be right that there are textbooks which use the moths as "examples of evolution" when they should be saying "example of natural selection".

Clearly natural selection is happening with the moths.

And, understanding natural selection is crucial to understanding evolution.

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Member (Idle past 1561 days)
Posts: 2965
From: Los Angeles, CA USA
Joined: 08-09-2005

Message 70 of 350 (261800)
11-21-2005 4:34 AM
Reply to: Message 42 by randman
11-20-2005 10:41 PM

Re: my response
Well, I won't be listing studies but I'll be approaching your points with reasoning.

1. First off, no the study does not rule out all the various factors that could have influenced whether lightly colored or darkly colored moths became more dominant as a result of soot. It could be something else entirely, perhaps another aspect of pollution, coincidence, etc,...

Yes, it may be a result of something other than predation. It could be that the moths themselves are being colored by the soot. However, I would suspect that all moths exposed would be effected the same in - just like when there is an oil spill, all the sea gulls that land in it get oil on them.

2. Secondly, birds have the ability to see in the UV spectrum and the ignorance of that basic fact renders moot any conclusions about what birds actually see in this instance.

The study that was posted a few messages back indicated that under UV the moths blended in better with the lichens. So, yeah, I think you were misreading it. (Or I am misreading it)

The other problem with the statement here is this - Birds have the ability to see in the UV spectrum, but they don't see exclusively in the UV spectrum, nor do all birds species see the same amount in the UV spectrum. So, even if darker moths were no different than light moths under UV light, they'd still have the edge given that the birds aren't seeing exclusively UV.

3. Peppered moths are nocturnal and so releasing them in the day-time to draw conclusions about their behaviour also makes the study based on faulty data.

Yes, the moths are nocturnal - meaning they are active at night and presumably flying at that time. Conversely, it means they are sitting still during the day. Even if the moths perfer to be high up in the tree, the branches up there are covered in soot as well.

The situation here is all about percentages. If being darker is slightly better than being lighter - weither high in the canopy or down on the trunks, it's going to be selected for. (or rather less selected against).

4. In reality, birds are not even the primary predator of peppered moths, but rather bats are. Bats method of sensing prey is totally different, and relies on sound waves and thus bats tend to capture moths in flight rather than while they are resting. This fact further makes the claims of the study to be somewhat fantastic in nature and without solid scientific standing.

While bats are the primary predator, the color shading is presumably not protective against radar. As a result, the group of moths as a whole - both light and dark - are subject to the same degree of predation from the bats. However, during the day, the dark moths fare slightly better than their light winged brothers. And that gives them the edge they need to outreproduce the competition.

5. I have heard but not verified that these same experiments were repeated elsewhere in the world with the opposite results. As such, since the experiment is not repeatable, it falls down on that merit as well.

I can't really respond to this since it is, by your own admission, somethng that you heard but haven't verified. I would suspect that these experiments, if they do exist, suffer from the same problems you pose in your criticism of the initial experiment. If you can find one or more of these, I invite you to post them - but please treat them to the same skeptical eye.

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Member (Idle past 1561 days)
Posts: 2965
From: Los Angeles, CA USA
Joined: 08-09-2005

Message 71 of 350 (261802)
11-21-2005 4:47 AM
Reply to: Message 58 by randman
11-21-2005 2:31 AM

Acting Batty
Whoa, Randman, you're on tilt here.

You say the primary predator is of no consequence? How do you know that?
Don't you have to offer real evidence for that?

For example, maybe some bats preferred the lighter moths and could distinquish them by their flying patterns, or maybe they craved the melatin or whatever made the darker moths dark, and there was a reduction in the bat population and so the darker moths were not eaten as much by bats?

Here's how we know, and yes I am generalizing.

Bats hunt by sonar. There has been no evidence presented that the white moths or the dark moths are any different in size. Size is the primary, if not only factor, in sonar detection of these moths in flight. As such, bats are going to be equally likely to feed on light and dark moths.

Natural selection works on multiple fronts at once. So all moths, light and dark, which are able to avoid bats are selected for. However, during the day, just the dark moths are selected for. The difference in pressure on these two groups resulted in the difference in population densities.

On the second part of your quote, you seem to be suggesting that the dark moths fly differently than the light moths, etc. Are you trying to say that they are in fact a different species and that speciation has occured here. I find it hard to believe that the behavior of the two months would change so radically based on just color.

It may just be that you are tired, or that you've been harassed to a frazzled point, but this post is a bit out there compaired to the other points you are making.

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Member (Idle past 1561 days)
Posts: 2965
From: Los Angeles, CA USA
Joined: 08-09-2005

Message 72 of 350 (261803)
11-21-2005 4:52 AM
Reply to: Message 62 by randman
11-21-2005 3:36 AM

Evolution means...
Good quotes.

Here's the problem, I think.

"evolution" can mean different things. It could mean "speciation". In which case, the moths is not a good example of it.

But, it could also mean "becoming better adapted to your environment" in which case the moths are a good example.

Personally, I think that the micro-evolution stuff leads to the macro-evolution stuff. But that's for another discussion.

The quotes you listed, if read as the definition I posted, really aren't that outrageous at all.

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Member (Idle past 1561 days)
Posts: 2965
From: Los Angeles, CA USA
Joined: 08-09-2005

Message 105 of 350 (262257)
11-22-2005 3:27 AM
Reply to: Message 99 by randman
11-22-2005 12:01 AM

Dark Moths, White trees.

You keep making the same point over and over, namely "the populations of dark moths increased in areas where the trees weren't subject to pollution and therefore not discolored."

I hear ya. Some aren't responding to it, which is frustrating. I'm sure that they have similiar complaints to air as well.

But, let's talk moths.

I assume that you listed a study that showed the population of dark moths increased in non-polluted areas. I'm even willing to accept that they did without a study, just for the sake of arguement.

But let's turn the same critical eye to this study that you have subjected the other studies to.

Were all the moths found in the non-polluted areas born there? Lived there exclusively? Could the study prove this? Seems like it would be extremely hard - sort of like finding leaves on the ground, and trying to put them back on the tree in place.

Moths, like butterflies, can travel often suprisingly long distances, (Look at Monarch migration). If a given large area - let's say 100 square miles contains both species of moth and one part of that area has pollution occuring in it, but the rest does not. The population densities of dark vs light moths is going to change. Unless it can be shown that the moths never move around, wouldn't population density changes in a part of the area naturally influence other parts?

I'm not saying your arguement is wrong, I'm just taking issue with some of the very strict criteria you want applied to the studies. Remember, nature isn't the lab. We don't have infinite control. There are always going to be unnamed factors and unknown influences.

If we are going to hold one study to this sort of rigorous testing, shouldn't we apply the same astute skeptical eye to everything? Even sites the many people here find misleading or even silly?

This message is a reply to:
 Message 99 by randman, posted 11-22-2005 12:01 AM randman has responded

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Member (Idle past 1561 days)
Posts: 2965
From: Los Angeles, CA USA
Joined: 08-09-2005

Message 106 of 350 (262259)
11-22-2005 3:34 AM
Reply to: Message 101 by randman
11-22-2005 12:13 AM

Extinction by predation
Jumping in on this one - though I haven't been following it nearly close enough.

It seems that we're (not entirely sure who's on what side) arguing that the change in population from light towards dark should result in the white moths eventual extinction.

But extinction do to predation (from species other than man) isn't all that easy. If the light moth population drops very low, but not to extinction levels, then the bird population must either likewise reduce or move to greener pastures. It doesn't take very many moths to keep the population in existance (not thriving mind you, simply alive).

So, it doesn't seem reasonable to me to expect white moth extinction in an area where neither the moth, nor bird, populations are restricted in their movement.

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