How Does Biological Evolution Deal With This?

i will also add this instance:

(image from reddit.)

and of course this impressive case:

we also need to ask what is the chance that these shapes\colors will exist in the genome in the first place. so even if such a pattern can evolve by small steps it doeosnt change the fact that the chance to get these patterns without design in the first place is very low.

Michael, your conceptual error here appears to be in thinking that all of the heritable variation on which selection acts is new variation that can only happen after selective pressures change. You’re missing the far more important concept that selection is constantly acting on already existing heritable variation.

If you can understand why a species is endangered because it lacks existing variation (polymorphism), just flip that around.

The idea that populations are static and “waiting” for new mutations to occur is a massive barrier to understanding. It’s one of Behe’s favorite false assumptions that seems reasonable to laypeople.


Why would we need to ask that, scd? What makes you assume that those pigments are proteins?

This is amazing! I am wandering what is the function of this mimicry. And how in the world such a thing could have been produced by the RV + NS mechanism?

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As far as I know, predators who attack the fly will aim for the wings instead of the body of the fly, allowing the fly to escape while only suffering wing damage. A similar phenomenon is seen with butterflies and their colorful wing patterns, which also often have very prominent eye-spots. Predators (such as mantises) will mistake the wings for the body and attempt to grab at the wings instead because they stand out.

See for example:
Prudic KL, Stoehr AM, Wasik BR, Monteiro A. Eyespots deflect predator attack increasing fitness and promoting the evolution of phenotypic plasticity. Proc Biol Sci. 2015 Jan 7;282(1798):20141531. DOI:10.1098/rspb.2014.1531

Mantid attack behaviours on dry season (DS) and wet season (WS) forms of Bicyclus anynana , and survival outcome for arena experiments. ( a ) The ventral surface of the two seasonal forms of B. anynana . Note the differences in the ventral hindwing eyespot size. ( b ) Latency for the invertebrate predator, Tenodera sinensis , to orient on each form of B. anynana . Means±95% CI presented. The DS form took longer for mantids to detect. ( c ) Percentage of butterfly escape once attacked by a praying mantid. The DS form was much less likely to escape once an attack was initiated. ( d ) Percentage of mantid first strike on various body parts of B. anynana . The WS form was attacked more frequently on the hindwings than the DS form. ( e ) Percentage of damage observed per hindwing eyespot in the WS form only. Eyespots Cu1, Cu2 and Pc were the most damaged.

It really takes just a tiny increased odds of survival between variants for certain traits to rise to high frequency in the population. Notice that it’s the same species of butterfly that goes through different stages in wing pigmentation. It is a very plastic trait, and they can alter the pigment expression across seasons.

And how in the world such a thing could have been produced by the RV + NS mechanism?

In all likelihood some pigment was already expressed in the wings to begin with, making them stand out more than the body did(the body color of this fly seems quite pale in comparison). Natural selection then shaped the pattern, with every increment having some small survival advantage.

Flies have many different pigment patterns in their wings:

If you can understand that having pigment expressed in the wings is a trait that exists in a population, and can vary between individuals(there is variation in the trait), and it is heritable. Then if you can accept that differences in this trait can have a survival advantage, the deal is sealed. That’s basically all that is needed. Take a look at wings with patterns like the O, P, and Q types above, which seems somewhat similar to the pattern from the fly with smaller flies on it’s wings.


To understand that, you have to look to developmental biology for answers, since development is the process that connects genetics and cellular biology to morphology. I always recommend the book “Life Unfolding” by Jamie Davies, which describes the process of human development from a single cell to a recognisable human body in a good amount of detail, with excellent explanations of many of the key processes involved.

To make a long story short, when you realise that these processes are really all variations of morphogen gradients and physical forces between cells, the question of how genetic changes can cause all manner of precise morphological (or pigmentation) changes becomes much easier to understand.


Thanks, John, for your explanation. Sadly, you have given me too much credit. I hadn’t so deeply contemplated this issue as you’ve described above. I really am just wondering how an evolutionary biologist (or other interested science professionals) looks at the coloration on this insect. The layperson will see an image of a damaged leaf superimposed on the back of the insect, intentional in its detail. The scientist., I presume, must not. They must see coloration that merely appears to be such, however it evolved. This is the crux of my question and why (initially) I asked how one unpacks this sort of occurrence.


Thanks Rum for this information!! Amazing the diversity of the patterns in the fly wings. So, is the coloration in these wings actually pigment? I always thought it was due to polarization or some sort of prism effect, similar to the rainbow pattern that is made by a small amount of oil floating on the water. (I assumed, I didn’t think this for cause.)

Similar to my initial question, when “eyespots” are mentioned, this description must merely be colloquial, right? It is not an intentional “eyespot” but just a pattern that evolved that appears similar to an eyespot, and happens to fool a predator into believing so as well.

because if the chance of that is very low it makes more sense that they are the result of design rather than natural process. so what makes you think that the chance that such a shape will exist in the first place is high? the second problem is how many changes are needed for such a camouflage (in the octopus case). as a designer, can you make a system that can make you almost invisible in a second by small steps? (it will be great as soldiers camouflage system).

“Merely appears”? Well, it may not arise from anyone’s (or any animal’s) intentions, but it certainly is no accident that it happens to make a cryptic resemblance. That is imposed by its predator’s (or its prey’s) visual system which has evolved to react strongly to the appearance of the mantis, and not to a leaf. Not sure why you keep saying that it is not “intention” but “merely appears”. It’s no accident that it resembles strongly a leaf, as leaves are what is around. Resembling, say, a cactus might be of no fitness advantage in a jungle.


here are more instances:

(its not a snake)

or this one:

too bad i cant post more than 2 links since i have many more.

(images from eureka and mako)

I’m not sure why you keep saying this either. If I were to paint a picture of a leaf, it would be intentional. If I were to dip a brush into paint and flick the brush toward a canvas, the paint would splatter onto the canvas. One could ask observers what the pattern reminded them of… whatever it reminded them of would merely appear to be an image of such. In the former example, the image would intentionally be of such.

When I look at the insect in question, I see a pattern that looks to be intentionally colored so as to mimic a leaf. A being can have intent. As you say, the appearance of this pattern is no mere accident, like the splotches of paint in my example. It would have been affected by aspects of evolution over time. It would not, however, be what it appears to most of us… an intentional image of a damaged leaf.

I’m not trying to trick anyone or get you to say anything you don’t want to say. I’m just trying to understand how you respond (intellectually) when you see something like this.

I don’t know specifically what is causing the rainbow effect, I was referring to the brown spots on the wings. The image is from this paper: Stable structural color patterns displayed on transparent insect wings.

There they write:

Genetic Control of the WIP.

The complex black pigment patterns that are repeatedly evolved in many groups of Diptera are formed and controlled by a set of spatiotemporal on/off switches for the single gene yellow (6, 7) and sometimes also involve other genes and physical wing traits (2, 4). An increasing body of evidence demonstrates direct parallels between development and regulation of wing patterns in distantly related groups such as Drosophila and butterflies (2, 7, 23, 30).

There are pictures of the wings with white and black backgrounds that make the different patterns stand out. When it comes to the fly pictured earlier, that has tiny fly patterns on the ends of it’s wings, I would have guessed they evolved from the brown spots similar to this picture: blackvswhitebackground

It’s not difficult to see how the dark spot at the tip of the left wing there could serve a similar survival advantage as the fly-image does: to direct attention and predator attacks away from the body of the fly, towards the tip of the wing.

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Presumably because you keep offering false dichotomies.

Right. That is an intentional image of a leaf.

And that will be neither intentional nor an image of a leaf. The pattern on a well-adapted insect, on the other hand, is not intentional, but it is an image of a leaf, created by natural selection.

I’m not sure you get to say how it appears to most of us. I don’t see any intent here.

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It’s not intentional by the insect Mike. It’s just natural selection acting on variations. Insects that happened by chance to look a little more leaf like (in color and shape) had a reproductive advantage over those who were not as leaf like. The leaf like ones produced more offspring and the whole population on average looked more leaf like. Over many generations the selection pressure produced a population with shape and color that looks very leaf like.

ETA: Here’s a short video illustrating the point.


This is no different to other functional structures. The earliest birds/bird-like theropods didn’t “intend” for wings to evolve in the specific way that they did, natural selection “guided” random variation to a functional form. Similarly, natural selection “guided” random variation in wing pigmentation to a functional pattern. The reason the pattern is functional is the same as the reason this thread exists - it represents either excellent camouflage or mimicry.


One, there is no “irreducible complexity” here. This is easily explicable in terms of incremental change.

Two, if such camouflage is by divine design, then it is designed for the avoidance and imposition of death in a predatory world. The more design is insisted upon, the more death planet becomes the object of creation. Camouflage is everywhere in the natural kingdom, much of it, as we have seen, quite extraordinaire. This speaks to the relentless struggle to survive in a world dominated by nature, red in tooth and claw.


I’m not nor was I ever trying to force anyone into any binary choices. I was asking the question trying to understand how scientists perceive visual objects such as this insect with a specific pattern on its back. If the choices I’ve offered are inadequate, every person who responds is welcome to answer in the way that best represents his own opinion.

It is? Are you sure? I don’t see how it can be an image of a leaf. I would say that it must be an image that only appears to look like a leaf.

Here’s an image that looks like a profile of JFK:


Here’s an image of JFK’s profile:

Both look like JFK. One is JFK and the other merely appears to look like JFK.

In the case of the insect that looks like the torn leaf, it would seem that one can only say that it looks like a torn leaf, not that it is an intentional image of a torn leaf.

I’m not trying to say how it appears to you. I was referring to the way that the layperson would perceive it. I would suggest that any layperson looking at the insect would say that it looks like a torn leaf. Do you disagree?

Thanks Tim. I understand this and appreciate it. The video was very cool! Thanks for sharing it.

Thanks and I agree and understand. My question was quite nuanced though. Obviously this insect is well-camouflaged. Incredibly so. Obviously the pattern looks like a leaf, as well. But it must have only ended up to have looked like a leaf, because it could not have intentionally done so. When humans mimic something, there is an intentional effort to appear (or sound) like something else. In evolution, this cannot be the case. Adaptations can result in a way that appears like a leaf, the same way the lava image appears to look like JFK.

I believe this to be so, else one would be invoking design in the human sense. If there is some other option, I’d be happy to entertain it.

I don’t really understand the distinction you’re trying to make here. Could you elaborate?


Okay, if an image of something is only an image of something because someone intends for it to be a image of something, then sure, leaf-insects aren’t images of leaves. They look like leaves, without being images of leaves. I’m not sure what was gained by insisting on this semantical distinction. Can’t we just say it’s an image of a leaf without necessarily having to think it’s intended?

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