Study proposes alternative way to explain life's complexity

Apr 12, 2013

Evolution skeptics argue that some biological structures, like the brain or the eye, are simply too complex for natural selection to explain. Biologists have proposed various ways that so-called 'irreducibly complex' structures could emerge incrementally over time, bit by bit. But a new study proposes an alternative route.

Instead of starting from simpler precursors and becoming more intricate, say authors Dan McShea and Wim Hordijk, some structures could have evolved from complex beginnings that gradually grew simpler—an idea they dub "complexity by subtraction." Computer models and trends in skull evolution back them up, the researchers show in a study published this week in the journal Evolutionary Biology.

Some are too dizzyingly complex to have emerged stepwise by adding one part and then the next over time, advocates say. Consider the human eye, or the cascade that causes blood to clot, or the flagellum, the tiny appendage that enables some bacteria to get around. Such all-or-none structures, the argument goes, need all their parts in order to function. Alter or take away any one piece, and the whole system stops working. In other words, what good is two thirds of an eye, or half of a flagellum?

For the majority of scientists, the standard response is to point to simpler versions of supposedly 'irreducibly complex' structures that exist in nature today, such as cup eyes in flatworms. Others show how such structures could have evolved incrementally over millions of years from simpler precursors. A simple eye-like structure—say, a patch of light-sensitive cells on the surface of the skin—could evolve into a camera-like eye like what we humans and many other animals have today, say.

"Even a very simple eye with a small number of parts would work a little. It would be able to detect shadows, or where light is coming from," said co-author Dan McShea of Duke University.

In a new study, McShea and co-author Wim Hordijk propose an alternative route. Instead of emerging by gradually and incrementally adding new genes, cells, tissues or organs over time, what if some so-called 'irreducibly complex' structures came to be by gradually losing parts, becoming simpler and more streamlined? Think of naturally occurring rock arches, which start as cliffs or piles of stone and form when bits of stone are weathered away. They call the principle 'complexity by subtraction.'

"Instead of building up bit by bit from simple to complex, you start complex and then winnow out the unnecessary parts, refining them and making them more efficient as you go," McShea said.

A used by co-author Wim Hordijk supports the idea. In the model, complex structures are represented by an array of cells, some white and some black, like the squares of a checkerboard. In this class of models known as cellular automata, the cells can change between black and white according to a set of rules.

Using a computer program that mimics the process of inheritance, mutation, recombination, and reproduction, the cells were then asked to perform a certain task. The better they were at accomplishing the task, the more likely they were to get passed on to the next generation, and over time a new generation of rules replaced the old ones. In the beginning, the patterns of black and white cells that emerged were quite complex. But after several more generations, some rules 'evolved' to generate simpler black and white cell patterns, and became more efficient at performing the task, Hordijk said.

We see similar trends in nature too, the authors say. Summarizing the results of previous paleontological studies, they show that vertebrate skulls started out complex, but have grown simpler and more streamlined. "For example, the skulls of fossil fish consist of a large number of differently-shaped bones that cover the skull like a jigsaw puzzle," McShea said. "We see a reduction in the number of skull bone types in the evolutionary transitions from fish to amphibian to reptile to mammal." In some cases skull bones were lost; in other cases adjacent bones were fused. Human skulls, for example, have fewer bones than fish skulls.

Computer simulations like Hordijk's will allow scientists to test ideas about how often 'complexity by subtraction' happens, or how long it takes. The next step is to find out how often the phenomenon happens in nature.

"What we need to do next is pick an arbitrary sample of complex structures and trace their evolution and see if you can tell which route they proceeded by, [from simple to complex or the opposite]. That will tell us whether this is common or not," McShea added.

Explore further: Rock-paper-scissors model helps researchers demonstrate benefits of high mutation rates

More information: McShea, D. and W. Hordijk (2013). "Complexity by subtraction." Evolutionary Biology. dx.doi.org/10.1007/s11692-013-9227-6

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Aaron1980
3.4 / 5 (10) Apr 12, 2013
Obviously these structures are inevitable given the laws of nature in our universe and sufficient time. There are equally obviously millions of similarly evolved living structures out there in the universe. They may not be close to us but they are out there.
RhabbKnotte
1 / 5 (6) Apr 12, 2013
It is one thing to contemplate a multiply boned skull and yet another to consider an eye. And the Brain, would it have followed the same evolutionary path? If we are descendants of the creatures that came before us, was some precursor creature born with an inordinately complex brain and every descendant specie wittled it away until left with a brain maximized for their evolutionary needs? Or has every specie evolved from a predecessor needed an instance of an individual born with a massively complex brain tailored to that specie? Not trying to be curt, I just can't fathom the connection.
Shootist
2.1 / 5 (7) Apr 12, 2013
It is one thing to contemplate . . . I just can't fathom the connection.


What you are not grasping is deep time.
twasnow
2.8 / 5 (4) Apr 12, 2013
It is one thing to contemplate . . . I just can't fathom the connection.


What you are not grasping is deep time.


You mean like *big puff* "whoa that deep time... MAN!"
twasnow
1 / 5 (8) Apr 12, 2013
rhabbknotte has a point.

More over the mere fact that it is necessary to contrive some simplification from complexity model shows there are some serious problems with current evolutionary theory. Please not that chaos is not complexity. To dismiss the problems is tantamount to scientific dogma.

(anyone who says there is no such thing as scientific dogma isn't paying attention, dogma is required until we understand everything, and I think understanding everything is highly unlikely to happen in the next few million years.)
cyberCMDR
5 / 5 (6) Apr 12, 2013
Basically what they're talking about here is that the original version of some feature might be a kludge, where existing parts come together in a configuration that provides an advantage. Decreasing the complexity of this kludge increases the efficiency, and therefore reduces the biological cost, providing further advantage.
Aaron1980
3 / 5 (8) Apr 12, 2013
Another way to look at it is that a jumble of random elements mixing randomly chaotically together without any scope in the universe would be the most complicated thing to maintain. Having every things organized and working most efficiently with sustainability and organizational purpose would be the simplest. Then we are evolving into simplicity by eliminating randomness and rendering things less chaotic.
Soylent_Grin
4.8 / 5 (4) Apr 12, 2013
Rhabbe, it's not "every" species or structure, it's one of several mechanisms that could result in usable complex structures.
Everything doesn't have to be just one way. Natural selection is true, it happens, but so does selective mating, gene drift, viral insertion, etc. They can all contribute to the evolution of a species.
In this case, complex structures can evolve from simpler ones, be a combination of other structures, or perhaps was already complex and got pared down. Or maybe all three contributed. Or maybe a fourth or fifth mechanism.
Don't fall into the thinking that if a process is discovered, all other known processes cease to be true.
PeterParker
1.8 / 5 (4) Apr 12, 2013
There is nothing new here as there is the only direction for evolution is increasing levels of genetic reproduction.
Tektrix
not rated yet Apr 12, 2013
There is nothing new here as there is the only direction for evolution is increasing levels of genetic reproduction.


Actually, evolution selects for species stability in a changing environment, which is why some species stop reproducing temporarily when resources become scarce. But the effect is the same in the long run.
Dug
1 / 5 (7) Apr 12, 2013
"Computer models and trends in skull evolution..." please, someone tell me what part of skull evolution was accomplished through computer modeling?
JVK
1 / 5 (6) Apr 12, 2013
...evolution selects for species stability in a changing environment, which is why some species stop reproducing temporarily when resources become scarce.


Once Darwin's nutrient-dependent pheromone-controlled 'conditions of existence' are met, adaptive evolution in a changing environment continues via ecological, social, neurogenic, and socio-cognitive niche construction. The ecological niche is nutrient-dependent; the social niche is pheromone-controlled and natural selection is for nutrients that metabolize to pheromones, which control reproduction in species from microbes to man.

The complexity of the first cell, which was obviously able to adaptively evolve into different cell types, involves molecular mechanisms that rival those involved in human learning and memory. Once the cell or organism learns what is not beneficial for its survival, it need no longer consider it in the context of nutrient-dependent pheromone-controlled species divergence.
Lurker2358
1 / 5 (12) Apr 12, 2013
Instead of emerging by gradually and incrementally adding new genes, cells, tissues or organs over time, what if some so-called 'irreducibly complex' structures came to be by gradually losing parts, becoming simpler and more streamlined? Think of naturally occurring rock arches, which start as cliffs or piles of stone and form when bits of stone are weathered away. They call the principle 'complexity by subtraction.'


An arch is topologically more complex than a solid. The analogy is incorrect because both a solid rock and an arch are inanimate objects with no codependent parts, such as a that from which a life form is made.

Moreover, it fails as an analogy because the authors claimed to be removing a component of a complex organism or organ in order to make a less complex organism or organ.

The entire premise is false, because you have ignored the issue of where the rock, the first organism, has come from.
Andragogue
4.8 / 5 (5) Apr 12, 2013
2/3 of an eye is better than no eye, even if it could only detect light and dark.
alfie_null
5 / 5 (4) Apr 13, 2013
An arch is topologically more complex than a solid. The analogy is incorrect because both a solid rock and an arch are inanimate objects with no codependent parts, such as a that from which a life form is made.

Moreover, it fails as an analogy because the authors claimed to be removing a component of a complex organism or organ in order to make a less complex organism or organ.

The entire premise is false, because you have ignored the issue of where the rock, the first organism, has come from.

We get the point. This conflicts with your religious beliefs. Which, by the way, are irrelevant to this field of study. It's a good analogy, if you can discard your bias.
JVK
1.6 / 5 (7) Apr 13, 2013
It's a good analogy, if you can discard your bias.

An approach to life's complexity that is "biased" by knowing the basic principles of biology and levels of biological organization required to link facts to their explanatory power is obviously relevant to this field of study. The topological complexity of arch formation is not! Religious beliefs have nothing to do with discussion of life's complexity; they do not change biological facts!
2/3 of an eye is better than no eye, even if it could only detect light and dark.

If that is true, why does eye regression occur in blind cave fish?
Sinister1811
1 / 5 (4) Apr 13, 2013
From simple to complex I can understand, but how can something go from complex to simple? Everything has to come from somewhere, and there isn't a creator.
JVK
1 / 5 (7) Apr 13, 2013
?...there isn't a creator? What does that have to do with biological complexity? You state your belief as if it were factually based.

Loss of eyes due to natural selection for increased tactile sensitivity is one general hypothesis for the convergent evolution of eye regression in cave fish. However, the cave fish environment is nutrient poor. That fact suggests to me that eye regression occurs as a trade off for enhanced ability to detect olfactory/pheromonal input. I am biased by my own model, nonetheless, and because adaptive evolution is nutrient-dependent and pheromone-controlled in species from microbes to man (e.g., whether or not the species has eyes or has ever lived in caves).
Mrshipley
2.3 / 5 (3) Apr 13, 2013
This theory is tosh (UK english for nonsense), and all it has done is give a bit more ammunition to the reality challenged creationists. Articles like this should not be given air-time unless they make a valid contribution to the debate.
who_me
1.6 / 5 (7) Apr 13, 2013
Theories of all types take faith, religious or not. No one would continue to test their theory if they didn't believe in it.
Complex to simple oh, I get it we blew up a 747 and got a tricycle, wait lightning struck my car and I looked out my window and it turned into horse. This is almost as good as the hopeful monster or evolutionary jump.
Lurker2358
1 / 5 (11) Apr 13, 2013
The theory would actually support the Christian theory of degeneration anyway, even though his Arch analogy was incorrect.
Moebius
3.4 / 5 (10) Apr 13, 2013
Yeah, hard to understand how an eye could evolve. From a light sensitive patch, to something covering it to moderate the light that changes to an iris, then another structure turns into a lens to focus which allows directional sight. Then muscles develop to move the line of sight instead of having to move the head and the ability to move it causes it to encapsulate and allow lids. Yeah, totally impossible.
JVK
1 / 5 (7) Apr 13, 2013
Yeah, hard to understand how an eye could evolve.

Try placing eye evolution in the context of cause and effect. What caused it to evolve? How did that cause enable its evolution. Simply put, try to add some biological facts to your understanding of eye evolution. Then use those facts to explain eye regression. If evolution goes both ways -- from less complex to more complex and back -- what is the role of the environment (i.e., Darwin's Conditions of Existence)? If the intracellular environment of the first cell contained the molecular mechanisms required for differentiation into different cell types (e.g., as indicated by what is known about the microRNA/messenger RNA balance), there is no problem whatsoever with nutrient-dependent pheromone-controlled adaptive evolution, additional complexity of the eye, or reversion to the already irreducible complexity of the first cell. What some people seem not to comprehend is the irreducible complexity of the first cell.
JVK
1 / 5 (6) Apr 13, 2013
... all it has done is give a bit more ammunition to the reality challenged creationists. Articles like this should not be given air-time unless they make a valid contribution to the debate.


What is your alternative reality? How are you able to determine what is a valid contribution to debate? If you believe in something, tell us HOW what you believe explains adaptive evolution. If you believe in nothing, we can compare your alternative reality to what is known about the biology of cause and effect. However, belief in nothing makes no valid contribution to the debate. It merely exemplifies ignorance of biological facts in the context of the reality of biologically based adaptive evolution.
beleg
1.8 / 5 (4) Apr 13, 2013
Do we do this - complexity by subtraction - on an inanimate basis?
The 75% Si02 glass casing of vacuum tubes became a substrate for the same functions that were first encased in glass tubes.
Of course, we were evolutionists for this lifeless evolution.
Still, we all agree there is evolution without life.
JVK
1 / 5 (5) Apr 13, 2013
Still, we all agree there is evolution without life.


-- as if saying this makes it true, especially in the context of "Study proposes alternative way to explain life's complexity."

This shows how far people are willing to go when it comes to discussion of life's complexity; they simply deny biologically based evolution to attempt discussion of evolution without life.
beleg
2.6 / 5 (5) Apr 13, 2013
Simply agree or disagree. Instead of:
-- as if saying this makes it true, especially in the context of "Study proposes alternative way to explain life's complexity."-JVK


Planets undergo evolution. Our planetary evolution is part of a biologically based evolution on earth. No attempt is made to discuss evolution without life.
No denial is stated (by anyone called "they") in an attempt to discuss evolution without life.
Fabricating confrontations where none exist defeats meaningful dialogue.
JVK
1 / 5 (5) Apr 13, 2013
Planets undergo evolution.

No. You just think that they do. The intelligent thing to do before telling others that planets undergo evolution would be to look at what Wikipedia has to say about it, or cite some other source. Wikipedia says: "Evolution is the change in the inherited characteristics of biological populations over successive generations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.[1]"

That's consistent with the report and topic discussion: "Study proposes alternative way to explain life's complexity" Somewhere out there is a place to discuss the evolution of planets. But that place is so far from the discussion here that you might as well be from another planet. Where did your brain and behavior adaptively evolve?
evolution3
not rated yet Apr 14, 2013
I think one might misunderstand this article because of the usage of "complex" or irreducibly complex.
It makes sense that some features may have had preavious states, that were much more complicated and then got more simple in that, but making it irreducibly complex. For example take the building of a bridge. You need a framework to build it, but once everythings in place, the framework becomes unneccessary and probably vanishes.
I wouldn't call that a new idea though. That additional parts may have existed to help the development of systems today isn't that new, so I don't quite understand why they call it a new approach. But the simulation is quite nice indeed.
JVK
1 / 5 (5) Apr 14, 2013
I think one might misunderstand this article because of the usage of "complex" or irreducibly complex.


I think that most people do not understand the complexity of systems biology, and that many would rather not attempt to understand it because of conflict with their ridiculous beliefs about cause and effect involving mutations theory. See for example Deep Homology of Arthropod Central Complex and Vertebrate Basal Ganglia [subscription required] http://www.scienc...abstract

Deep homology is ensured if divergence of species via adaptive evolution is nutrient-dependent and pheromone-controlled, which it obviously is in species from microbes to man. Homology exists by chance if mutations cause speciation over "deep time" via accumulation of mutations that are not detrimental.

Compare the facts of "deep homology" to the theory of "deep time" to see whether or not you exist in the real world of nutrient-dependent pheromone-controlled life.
geokstr
1 / 5 (5) Apr 14, 2013
2/3 of an eye is better than no eye, even if it could only detect light and dark.

If that is true, why does eye regression occur in blind cave fish?

Because in a totally dark environment, a light detector of any kind becomes irrelevant and will atrophy over time. It is only of competitive advantage over those critters without a light detector in an environment where being able to detect light allows for better survival.
JVK
1 / 5 (4) Apr 14, 2013
...in a totally dark environment, a light detector of any kind becomes irrelevant and will atrophy over time. It is only of competitive advantage over those critters without a light detector in an environment where being able to detect light allows for better survival.


Who turned on the lights and invited organisms to detect it and compete for it via the adaptive evolution of eyes unless they returned to the caves like cave fish with eyes that regressed? Did you forget that the topic here is life's complexity? Do you not understand that the complexity of evolved eyes must follow from the complexity of Darwin's conditions of existence? Natural selection that enabled the adaptive evolution of eyes is nutrient-dependent and pheromone-controlled as is all adaptive evolution. How does one organism that's unable to detect light evolve into one that can detect light and select a mate that somehow also evolved to detect light so that their offspring inherit primitive eyes?
ODesign
5 / 5 (1) Apr 15, 2013
Evolution of the eye is explained very clearly by wikipedia. You don't need to speculate at all it's well researched.
http://en.wikiped..._the_eye

I don't think this theory is very new or maybe it's just not reported in a way that explains the news part clearly.

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