## Sunday, December 27, 2009

### The Amazing Mantis Shrimp

You have probably heard of polaroid sunglasses which reduce glare. You may also know that if you rotate the glasses (or your head while you're wearing the glasses) the glare becomes stronger. This is because the sunglasses reduce glare in only one dimension. Light waves can have any orientation. Like waves in a pond, light waves can move upward and downward as the light travels forward. But unlike waves in a pond, light waves can also move from left to right and back, as the light travels forward. These two orientations are referred to as vertically and horizontally polarized light, respectively. But light is not restricted to one or the other--in general a light wave consists of both a vertical and a horizontal component. Purely vertical and horizontal light waves are special cases. And if you combine the vertical and horizontal components you obtain a wave that rotates as it travels forward. For example, the wave can rotate in a circle. But again, this is special case. In general, a light wave maps out an ellipse as it travels forward.

If all of this is confusing, don't worry. All you need to understand is the general idea that light waves can be polarized in different, complicated ways. These concepts are important to engineers and physicists who, for example, work in communications. Television and radio station transmitters and antennae, cell phones and transmitters, and the many other conveniences we enjoy are all carefully designed incorporating these concepts. For instance, CD and DVD players need to convert the vertically or horizontally polarized light to circular polarization.

But once again, after we understand and develop a new technology we find it was present all along in nature. In this case, mantis shrimps not only control the polarization of light waves, but they do it better than our best devices. The CD and DVD players, for instance, use a quarter-wave retarder that converts the polarization but only at a single color of light. The mantis shrimp makes the conversion across a broad spectrum of colors. Here is the abstract of a recent paper on the exploits of the mantis shrimp:

Animals make use of a wealth of optical physics to control and manipulate light, for example, in creating reflective animal colouration and polarized light signals. Their precise optics often surpass equivalent man-made optical devices in both sophistication and efficiency. Here, we report a biophysical mechanism that creates a natural full-visible-range achromatic quarter-wave retarder in the eye of a stomatopod crustacean. Analogous, man-made retardation devices are important optical components, used in both scientific research and commercial applications for controlling polarized light. Typical synthetic retarders are not achromatic, and more elaborate designs, such as, multilayer subwavelength gratings or bicrystalline constructions, only achieve partial wavelength independence. In this work, we use both experimental measurements and theoretical modelling of the photoreceptor structure to illustrate how a novel interplay of intrinsic and form birefringence results in a natural achromatic optic that significantly outperforms current man-made optical devices.

You can go here for a good description of the amazing mantis shrimp (optics is not its only speciality) and its most advanced vision system.

And what does evolution have to say about this? Only that it all evolved, somehow. Some mutations happened to occur, fantastic new designs emerged, and they stuck.

As silly as that sounds, it gets worse. As we have discussed before, the amazing optics hardware is only one of the essential components of the design. Without the processing logic and hardware, and behavior algorithms that use the processed signals, the upfront optics hardware, as fantastic as it is, is as useless as a jet engine is without the jet.

1. "And what does evolution have to say about this? Only that it all evolved, somehow. Some mutations happened to occur, fantastic new designs emerged, and they stuck."

A specific, testable assertion. As a scientific theory should.

What, by contrast, does design theory have to say about it? Anything at all?

2. Ritchie:

"What, by contrast, does design theory have to say about it? Anything at all?"

How is that relevant?

3. I wanted to see if design theory could behave as a scientific theory should by producing a specific, testable, falsifiable assertion of its own.

Apparently not.

Another example then that design theory is simply not a scientific theory.

4. This comment has been removed by the author.

5. The difficulty with evolution is that it can be used to explain anything and everything, and therefore nothing, because it makes apriori philosophical assumptions. One of the most important assumptions is that all existing biological phenomena must have come about by evolution. Thus it assumes the consequent (a logical fallacy): if we see some biological feature, it must have a naturalistic, materialist, evolutionary explanation. What is disguised (usually unknowingly) in the evolutionary explanations is the hidden assumption that everything biological has the same explanation - evolution - which is always the cause. In that respect, saying "evolution did it" is no different from saying "God did it".

The only way to get beyond that impasse is to test if there are limits to evolution; we are finding that there are limits. So, then, how do we explain those limits? Or do we resort to "evolution of the gaps" or, "I don't know how the hell it happened by evolution but evolution must be the explanation; I have faith that we will find a materialist evolutionary explanation".

Evolution is great on potential driving forces (e.g., mechanisms of natural selection), but very very poor on mechanics. Take for instance feathers. What is the sequence of DNA changes from primitive hairs to feathers? No one knows. In fact, no one has a clue. But speculations on driving forces? oh, they are legion: gliding from trees, bigger and longer hops, faster running, extra warmth, mate selection, etc. Lots of just-so stories.

regards,
#John

6. "The difficulty with evolution is that it can be used to explain anything and everything, and therefore nothing,"

Well that's not true. Evolution could not explain the gene sequence of every animal species on the planet being unique. Or the appearance of complex creatures or features without the existence of precursors showing 'intermediate' stages of development. But this is not what we find. The gene sequences of animal species and the existence of 'intermediate' creatures and features very much supports the ideas of common descent and evolution by natural selection.

"One of the most important assumptions is that all existing biological phenomena must have come about by evolution."

Is there a single scientific theory which can explain existing biological phenomenon without evolution? Until there is one, evolution is all we have to work with.

"In that respect, saying "evolution did it" is no different from saying "God did it"."

I disagree. We are justified in assuming 'evolution did it' beacuse we know for a fact evolution happens. There is a plethora of evidence supporting it. If we say 'God did it' we are invoking an explaination which is supported by precisely no evidence, is totally speculative at best, as may not even make sense in and of itself.

"The only way to get beyond that impasse is to test if there are limits to evolution; we are finding that there are limits."

Are there? Such as?

"the sequence of DNA changes from primitive hairs to feathers? No one knows."

Not true.
http://ncsce.org/PDF_files/feathers/nature.pdf