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OfflineSeussA
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Evolution, specializtion, and natural selection
    #4735397 - 09/30/05 08:47 AM (12 years, 25 days ago)

With all the discussion over intelligent design (ID), evolution, and creationism recently, I thought I would try to express a theory I have about evolution. I have been running computer based evolution simulations for the last ten years and have come to some interesting conclusions regarding evolution and speciation. I contend that evolution is driven by mass extinction and hindered by natural selection.

In a closed population, natural selection tends to specialize a species. As a species becomes specialized, the unfit characteristics of that species are pruned. Occasional mutations occur, but the mutated organisms are almost always less adapt at survival than the specialized organisms. The mutations are quickly pruned from the population through natural selection.

Evolution only occurs when natural selection has been suppressed. When a mass extinction occurs within a closed population, the surviving organisms are no longer constrained by natural selection. There are no more predators or environmental obstacles to cull the population. As the population expands without constraint (or competition), mutations are able to survive. As the population continues to grow, natural selection once again will begin steering the population towards specialization. Differences in the child populations due to mutations create speciation as natural selection specializes each niche independently.

For evolution to occur, populations must be able to pass on mutations to their decedents. These mutations must be able to survive for several generations or they will be culled from the population rather than integrated into the population. The only way for the mutations to survive long enough to become a normal part of a population is if natural selection is no longer steering the population towards specialization. In essence, mass extinction creates an environment that allows for populations full of diversity while natural selection takes a diverse population and prunes away all the characteristics that do not help with survival.

If this theory is correct, then fossil records should indicate a large increase in different species occurring immediately after a mass extinction followed by a long and slow process of specialization of each new species. Many of the new species will die out over time as natural selection allows only the most fit species to survive. During this time new species will not be created; instead existing species will continue to specialize or die out.


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Offlinefreddurgan
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Re: Evolution, specializtion, and natural selection [Re: Seuss]
    #4735511 - 09/30/05 09:51 AM (12 years, 25 days ago)

The fossil record pretty much shows what you are talking about.

The Permian extinction, around 250 million years ago. Wiped out about 96% of marine species and killed many terrestrial life.

Around this time, the first large radiation of reptiles and modern day insects occured.

And when I say around this time, I mean..within 5-10 million years. A blink of an eye in the history of life.

Around 200 million years later, once those reptiles had taken over the world and become dinosaurs, they all died in the Cretaceous mass extinction. Around that time, flowering plants began to appear, as well as the largest radiation of mammals, birds, and pollinating insects.

So..it does look like there were two mass shifts. Oceanic creatures -> dinosaurs -> mammals. However, there is already a term for what you are talking about.

Adaptive radiation - The emergence of numerous species from a common acestor introduced into an environment that presents a diversity of new opportunities and problems.


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InvisibleGijith
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Re: Evolution, specializtion, and natural selection [Re: freddurgan]
    #4735600 - 09/30/05 10:34 AM (12 years, 25 days ago)

Yeah, this idea has been floating around for a while and is accepted by most of the people who study such things.

The 5 mass extinctions that are shown in the rock record are all followed by an extreme increase in biodiversity (actually, we can only really make accurate statements about 4 of them). Though it's very difficult to examine, there's also some evidence to suggest that these worldwide jumps might also have some correlation to magnetic reversals.

What's interesting is that sedimentary geologists are starting to show that this occurs on a much smaller scale as well. You can see an increase in species following a fairly local catastrophic event, such as a massive flash flood or a volcanic eruption.

I skimmed through a book on this once. 'Future Evolution' by Peter Ward. There's a bunch of others.


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OfflineSeussA
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Re: Evolution, specializtion, and natural selection [Re: Gijith]
    #4736084 - 09/30/05 12:32 PM (12 years, 25 days ago)

> Yeah, this idea has been floating around for a while and is accepted by most of the people who study such things.

Cool.  I came up with the idea based on the results of hundrends upon hundreds of hours of simulated evolution.  For the longest time I thought my code was incorrect... but when I started culling the populations, all of the sudden the virtual organisms would begin to evolve towards a global rather than local solution.

> You can see an increase in species following a fairly local catastrophic event,

As long as the population is closed, then relatively speaking, a local catastrophic event would still be a "global" event within the niche.

Thanks for the input.  :smile:


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InvisibleTODAY
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Re: Evolution, specializtion, and natural selection [Re: Seuss]
    #4736100 - 09/30/05 12:35 PM (12 years, 25 days ago)

isn't your theory the theory the scientific community currently accepts??


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OfflineCatalysis
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Re: Evolution, specializtion, and natural selection [Re: Seuss]
    #4738606 - 09/30/05 10:19 PM (12 years, 25 days ago)

Hmmm..Read my second post in "Are birds dinosaurs?".

Basically my thought is that all species that we know as avians descended from a very select few dinosaur species after the Great Extinction. This is why paleontologists have such a hard time finding winged, feathered dinosaurs yet current phylogeny tends to put all avians as descendents of dinosaurs.

I think you have an interesting point. I will keep an eye out for more supporting evidence.


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OfflineLiquidSmoke
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Re: Evolution, specializtion, and natural selection [Re: TODAY]
    #4739614 - 10/01/05 02:49 AM (12 years, 25 days ago)

Quote:

TODAY said:
isn't your theory the theory the scientific community currently accepts??





Yeah I was just about to say. Suess basically described what's coined as "disturbance effect" or "punctuated equilibrium". Where if it isn't for large disturbances in the ecosystem of a given area, you wouldn't have rapid development of new species who would normally be predominated by an established system.

This theory already exists, and it's pretty much supported fairly widely by ecologists.


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OfflinetrendalM
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Re: Evolution, specializtion, and natural selection [Re: Seuss]
    #4745223 - 10/02/05 02:36 PM (12 years, 23 days ago)

If this theory is correct, then fossil records should indicate a large increase in different species occurring immediately after a mass extinction followed by a long and slow process of specialization of each new species.

I'm quite sure this is what the fossil record indicates, and I also came to much the same conclusion about a year ago.

I think it is the extinction events themselves which cause speciation to occur. During the millions of years in-between the large extinction events mutations would not all be culled by the process of specialization. The ones causing physical impairment would, but many other mutations could occur that do not appreciably affect the functioning of an organism. These kind of mutations could easily spread through specific populations without notice. When a mass-extinction occurs, some of these unused mutations may quickly become advantageous - such that those who had the mutation would survive longer than those who didn't.

I agree that the process of specializations does tend to "smooth" things out over time, resulting in a more-or-less homogeneous species, but I think the un-affective mutations could build up in some populations despite (or perhaps in concert with) the drive towards specialization.

It seems much more plausible to me that advantageous mutations would exist before the pressure of an extinction occurs, rather than develop extremely quickly during the extinction event.


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