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Darwin and Evolution


The D.S.

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Again, no. It's not. Complexity has nothing to do with it. An organism (and it's genetic make-up) can be incredibly simple and basic and yet that organism can still be incredibly adapted and successful in it's given environment. Just look at protoctists.

 

 

Yes, and the evolutionary process is also at a stand still.

 

A person with a limited work history, a simple mind and low tolerance for change, may well find a happy niche as a grave digger, but on the other hand a person with several degrees and a diverse work history will more likely evolve as a person.

 

Evolution is the subject at hand, or am I mistaken?

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:juggle: How 'bout suitably adaptable, or suitable adaptability?

 

 

 

Sometimes genetic complexity can prove disadvantageous to suitable adaptability.

 

:juggle: What?

 

 

The environments in which organisms evolve can, however, be portrayed in at least two

ways – first, in terms of their stable or consistent features, i.e., the stable qualities that make a habitat recognizable; and second, in terms of their dynamic qualities, the variable properties of an environment to which an individual organism and its genetic lineage must accommodate if either is to persist.

Adaptability can be defined in terms of three qualities: the ability of an organism to persist through environmental shifts, to spread to new habitats, or to respond in novel ways to its surroundings.

 

http://http://www.uchicago.edu/aff/mwc-amacad/biocomplexity/conference_papers/PottsComplexity.pdf

 

 

 

 

The Complexity Response

If the emphasis accorded here to dynamic environmental properties is correct, it implies

that buffering mechanisms should characterize biological systems. Buffering mechanisms

should be apparent over a wide time spectrum and at various biological scales of organization

– from metabolic buffering inside individual cells (on very short time scales) to ecological

buffering by lineages of organisms in response to long-term instability. These means of

adjusting to environmental dynamics are likely to represent important aspects of evolutionary

biocomplexity (Table 3).

• At the genomal level, unstable selective conditions may yield an increase in genetic

polymorphism; complexity arises from building a larger storehouse of alternative

genetic variations.• At the developmental level, inconsistency in environment and selection may lead to

a greater degree of phenotypic plasticity; complexity arises, in this case, from

genotype-environment interactions that expand the developmental reaction norm.

• At the behavioral and ecological level, environmental instability may enlarge a

lineage’s adaptive versatility; complexity results from decoupling the organism from

any single habitat and a freer mapping of its behavior on to environment.

In the behavioral and ecological domain, organisms evolve ways of tracking favored

foods or climate conditions and/or sophisticated behavioral mechanisms that can engender

versatile responses to new environments. The latter may entail decoupling of the organism

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A person with a limited work history, a simple mind and low tolerance for change, may well find a happy niche as a grave digger, but on the other hand a person with several degrees and a diverse work history will more likely evolve as a person.

 

Evolution is the subject at hand, or am I mistaken?

 

We are talking about biological evolution. From your analogy, it appears you are talking about an individuals growth during life. The two have little in common.

 

Species that become overly specialized may suffer more than more generalized species when the environment changes. Complexity IN THIS CASE is a bad thing.

True, there are some cases where complexity is a good thing and allows a species to adapt to changes, however there are also cases where complexity is selected against.

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It [Darwinian evolution] has nothing to do with complexity, it has to do with suitability to one's environment. :shrug:
It is not suitability…
In an absolute, yes/no sense, suitability is critical to Darwinian evolution: an organism that is unsuited to its environment has no descendents, becoming extinct, while one that is, even if very “poorly” as measured by its population size, has descendents, and does not become extinct.
… as much as adaptability and adaptability is dependent on genetic complexity.
While it’s reasonable, and with difficulty, experimentally verifiable, that increased genetic “complexity” …

Before continuing, a sidebar on terminology:

The term “genetic complexity” isn’t a common term in genetic biology literature.

 

It’s most common use is to describe not a trait of an organism’s entire genome, but a trait of a particular “
”, the number of
(a complicated term, that, for the sake of this post, can be taken to mean “a contiguous sequence of base pairs in a genome that: 1) are switched on (promoted) and off as one; 2) produce (express) a single or a related collection of proteins”) involved in producing the trait.

 

Another not uncommon technical use refers to interaction among communities of organisms that promiscuously use DNA and RNA to exchange information, such as bacteria

 

From a cursory web search of the phrase “genetic complexity”, the only occurrences of the term I find that are applied to entire genomes are on sites promoting the pseudoscience of
(such as
– which, in fairness to the site, despite its provocative name, has some reasonable skeptical discussion in its forums)

 

Therefore, I’ll take the term “genetic complexity” as used in Thunderbird’s post to mean “size of genome” (
), a readily measurable trait of an entire genome

… allows an organism to respond to changing conditions, decreasing its likelihood of extinction, this is not the only reasonable mechanism. The main idea behind this hypothesis is that large genes may be switched off for many generations, then switch on when unusual conditions appear to change the organisms traits. For example, a normally energetic, rapidly reproducing micro organism may become dormant when vital resources, such as water, disappear, allowing it to survive climactic events such as droughts.

 

Another common strategy for adapting to changing conditions is mutation. This strategy appears to be very successful in many organisms with very small genomes. The main idea behind this hypothesis is that, rather than carry large genomes with many inactive genes, the organism can reproduce with low “genetic fidelity” to produce subsequent generations with significantly different genes and traits. Although most variants won’t survive, some may, out competing and reproducing their parents and competitors.

 

A final few notes, which may be well known to many readers, but is important to disabuse others of a common misconception:

  • Physical complexity, such as having specialized tissues and large bodies, is not strongly correlated to genome size. Many single-celled microorganisms (ie: protozoa) have larger (as many genomes than any multi-celled organism (eg: humans)
  • Physical “modernity” in animals – having a physical form appearing more recently than “archaic” animals (eg: sharks and crocodiles) is also not correlated to genome size. Lungfish, for example, appear nearly unchanged in the fossil record since the Devonian period, about 400 million years ago, yet all members of the order have genomes 10 to 100 times as large as the largest mammal species.
  • Humans and other “smart” animals have unremarkable genome sizes, about twice as large as the smallest mammal genome, and about half the size of the largest.

Source: Gregory, T.R. (2005). Animal Genome Size Database. http://www.genomesize.com

 

In short, Darwinian evolution, though a simple high-level concept, appears to be very complicated in its biochemical implementation. Simple generalizations about molecular biology – such as the idea that it tends to produce larger genomes or more complicated QTLs – appear to me to be overly simplistic, unhelpful, and simply incorrect.

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In short, Darwinian evolution, though a simple high-level concept, appears to be very complicated in its biochemical implementation. Simple generalizations about molecular biology – such as the idea that it tends to produce larger genomes or more complicated QTLs – appear to me to be overly simplistic, unhelpful, and simply incorrect.

 

 

 

True, and no one was saying that. Which makes this post irrelevant to the subject being debated that "Complexity has nothing to do with evolution"

 

Life can ether, be static or become more complex. You could learn more about the evolutionary process by observing something that actually changes, than something that does not. If not for the increase in complexity evolution would not take place.

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If not for the increase in complexity evolution would not take place.

 

That's not really true.

 

Consider a wood rat population. The population could stay at the same "complexity" yet, through evolutionary processes such as genetic drift, evolution can occur.

 

I guess it really depends on your definition of "complexity". CraigD asked you, in his last post, what your definition of "genetic complexity" is. He went ahead with the assumption that you meant "size of genome". Is this correct?

 

Philosophically speaking, some have argued that complexity does increase (yet complexity is ill-defined and seems largely subjective). Here's a good philosophical article that you might enjoy TB.

 

http://pespmc1.vub.ac.be/Papers/ComplexityGrowth.html

 

At least since the days of Darwin, the idea of evolution has been associated with the increase of complexity: if we go back in time we see originally only simple systems (elementary particles, atoms, molecules, unicellular organisms) while more and more complex systems (multicellular organisms, vertebrates, mammals, human beings) appear in later stages. Traditional evolutionary theory, however, had no methods for analysing complexity, and so this observation remained a purely intuitive impression. The last decades have seen a proliferation of theories offering new concepts and principles for modelling complex systems: information theory, general systems theory, cybernetics, non-equilibrium thermodynamics, catastrophe theory, deterministic chaos, complex adaptive systems, etc. These have led to the awareness that complexity is a much more important aspect of the world than classical, reductionist science would have assumed.

 

Paradoxically, this development has also been accompanied by a questioning of the idea that complexity necessarily grows during evolution. It turns out that complexity is itself a complex concept: difficult to define and to model, and easy to misinterpret. To a certain extent, complexity is in the eye of the beholder: what is complex for one observer, may be simple for another one. This awareness is reinforced by the wider intellectual climate, characterized by a "post-modern" philosophy, which stresses the subjectivity or culture-dependence of all scientific models. To this must be added the continuing trend away from anthropocentrism, which was started by Copernicus' insight that the Earth is not the center of the solar system, and Darwin's discovery that humans and animals have a common origin. The "growth of complexity" idea can be and has been used to argue that humanity, though it may no longer be at the center of the universe, is still at the top of the evolutionary ladder (Gould, 1994). The present relativistic ideology, which tends to put all people, theories, cultures and even species on an equal footing, shies away from the implied idea of a ladder or hierarchy of complexity, and therefore rejects the whole growth of complexity argument.

 

On the other hand, concrete observations in diverse domains seem to confirm in ever more detail the intuitive notion of increasing complexity...

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That's not really true.

 

Consider a wood rat population. The population could stay at the same "complexity" yet, through evolutionary processes such as genetic drift, evolution can occur.

 

I guess it really depends on your definition of "complexity". CraigD asked you, in his last post, what your definition of "genetic complexity" is. He went ahead with the assumption that you meant "size of genome". Is this correct?

 

Philosophically speaking, some have argued that complexity does increase (yet complexity is ill-defined and seems largely subjective). Here's a good philosophical article that you might enjoy TB.

 

 

Genetic complexity can be applied to the genome in its self, or to the variety of species that it gives rise to though genetic drift. In this contexts, complexity would be defined as the opposite of homogeneity.

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Genetic complexity can be applied to the genome in its self, or to the variety of species that it gives rise to though genetic drift. In this contexts, complexity would be defined as the opposite of homogeneity.

 

Your post implies that genetic drift would never result in an organism which is less complex than it's ancestry, which it often does, so you're wrong.

 

Many times, a decrease in complexity (an increase in simplicity) is selected for. Why is this so hard for you to grasp?

 

Repeating yourself does not add any validity to your claims. :shrug:

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Genetic complexity can be applied to the genome in its self, or to the variety of species that it gives rise to though genetic drift. In this contexts, complexity would be defined as the opposite of homogeneity.

 

So it seems you are saying that the genetic complexity (GC) of an organism is determined by its potential to produce variation. Is this an accurate interpretation of what you stated?

 

If so, can you provide sources to back up your claim? How do you scientifically determine GC?

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:shrug:

 

I would be wrong if that is what I said, which course I did not.

 

Try again.

 

This is true, and also irrelevant, since no one is arguing against that.

 

Yeah... silly me, actually reading your words. :hyper:

 

 

 

Life can ether, be static or become more complex.

It can also become more simple.

 

 

If not for the increase in complexity evolution would not take place.

Specifically, this is the sentence which you claim you did not say, and which you said you were not arguing.

 

 

Let's repeat it again here for emphasis:

 

Thunderbird: "If not for the increase in complexity evolution would not take place."

 

I take that to mean that complexity is at the heart of evolution, and that without increases in complexity evolution would not happen. I've been arguing that this is false, as sometimes a decrease in complexity is selected for.

 

 

If I've misinterpreted you, then I apologize, but perhaps you should be more clear in your points henceforth, as I still don't see how you are NOT saying that evolution requires an increase in complexity.

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Increasing complexity could describe the entire evolving organism, but the DNA can get simpler and still lead to more complexity. Fruits flies have more DNA than humans, but humans are more complex. What this implies it is not the size of the DNA that counts, but how the genes are arranged. The DNA can randomly mutate and add more DNA and we get a fruit fly. Or the DNA can skinny down and arrange itself better in space and we get a human. Is genetic rearrangement a mutation affect or is it a simple chemical potential trying to lower overall energy?

 

When you think in terms of multicellular differentiation, each cell has the same DNA. It is not mutations within each cell that defines which will be a nerve or a blood cell. It has to do with genetic accessibility. Conceivably one could have a complex starter cell that rearranges the genes of subsequent daughter cells into a dozen different configurations, over time, without changing any gene content. We could get twelve different types of cells without requiring any mutations. But mutations get all the credit.

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Yeah... silly me, actually reading your words. :shrug:

 

 

 

 

It can also become more simple.

 

 

 

Specifically, this is the sentence which you claim you did not say, and which you said you were not arguing.

 

 

Let's repeat it again here for emphasis:

 

Thunderbird: "If not for the increase in complexity evolution would not take place."

 

I take that to mean that complexity is at the heart of evolution, and that without increases in complexity evolution would not happen. I've been arguing that this is false, as sometimes a decrease in complexity is selected for.

 

 

If I've misinterpreted you, then I apologize, but perhaps you should be more clear in your points henceforth, as I still don't see how you are NOT saying that evolution requires an increase in complexity.

 

I jumped in this debate with this statement of yours "It has nothing to do with complexity, it has to do with suitability to one's environment." You referring to evolution. Correct ?

 

 

This statement negates complexity completely.

 

Complexity, which I have defined as the opposite of homogeneity. Is in fact an Integral to change.

Change is Integral to evolution.

 

You are overly arguing the point that a life form does not need to become complex to be successful. No kidding !

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I jumped in this debate with this statement of yours "It has nothing to do with complexity, it has to do with suitability to one's environment." You referring to evolution. Correct ?

 

 

This statement negates complexity completely.

 

Complexity, which I have defined as the opposite of homogeneity. Is in fact an Integral to change.

Change is Integral to evolution.

 

You are overly arguing the point that a life form does not need to become complex to be successful. No kidding !

That's fair, but isn't heterogeneity the opposite of homogeneity? Why call it complex? Relationships are complex. Higher dimensional math is complex. The parts of an organism which are selected for during the evolutionary process? Not so much...

 

Also, complexity is subjective, and not a very useful approach in studies of evolution. It's not very qualitative.

 

Either way, you're refering to heterogeneity, not complexity.

 

 

In science, the precise definition of words is quite important. :naughty:

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That's fair, but isn't heterogeneity the opposite of homogeneity? Why call it complex? Relationships are complex. Higher dimensional math is complex. The parts of an organism which are selected for during the evolutionary process? Not so much...

 

:naughty:

 

Your correct if you just look at parts, I see evolution more as a system.

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