Is evolution dictated entirely by circumstance?

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CaptainTrips222
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01 Jul 2011, 1:26 pm

What other factors prompt changes in a species?



MollyTroubletail
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01 Jul 2011, 1:33 pm

It's a great question, but unfortunately there is no simple answer. There's an entire huge field of study and research in the very question that you're asking.

Essentially, evolution is driven by selective pressure acting on natural genetic variation. But this statement is a vast over-simplification, of course. You could read tomes about it every day for a year, and still come out scratching your head over it and full of more questions than previously.



ruveyn
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01 Jul 2011, 2:56 pm

CaptainTrips222 wrote:
What other factors prompt changes in a species?


Conceivably selective breeding. We have created new sub-species of plants and animals by selective breeding. Look at dogs for example. There are sub-species of dogs which exist only because humans selectively breed them.

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Vexcalibur
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01 Jul 2011, 6:50 pm

Why do you mean by circumstance?


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Philologos
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01 Jul 2011, 6:58 pm

Politics? Philosophy? Religion?

Not a big deal, just wondering how you see it.

The question does need some expansion to be clear. What COULD there be that is not circumstances? Even divinely guided modification or Nature subconsciously aiming toward a goal would be "circumstances".



Sand
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01 Jul 2011, 8:03 pm

Ruveyn seems to exempt human intervention from "circumstance". Several of the natural forces have time factors that radically change the machinery of evolution. They are not essentially different from other forces but cataclysms such as rapid changes in the chemistry of the atmosphere or the oceans may be too violent for the slower processes involved in evolution to counter for the survival of large numbers of species. There is strong evidence today that such changes are now taking place and major species variations are being irretrievably lost very rapidly. Beyond the loss of any particular species, there are repercussions in associated species and even in the basic chemical complex upon which all life depends. Specialists are aware of this but the bulk of humanity is not only ignorant of the current developing disaster but determinably resistant to recognize it or make the critical adjustments needed to survive. Humanity, for all its vaunted supposed intellect will, in the very near future, discover it is not immune to the results of this vital neglect.



ryan93
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01 Jul 2011, 9:14 pm

Evolution occurs because some traits offer reproductive advantages (survival advantages being a subsection of this). If a gene gives an organism a reproductive advantage (down to sexual, artificial or natural selection, or even cultural influences), the gene will increase in frequency.

I hope that when you say "circumstance", you don't imagine the alternative is teleology.


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naturalplastic
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01 Jul 2011, 10:11 pm

Circumstances?

As opposed to what?

The environment applies selective pressure to the gene pool of a population of organisms for certain traits.

Every change in the envirionment is a ""circumstance".

Even domestication, even a global mass exticntion due to a asteroid,- you might even say that God intervening is a "circumstance".



Philologos
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01 Jul 2011, 10:13 pm

No visible clarification yet.



ruveyn
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02 Jul 2011, 10:01 am

Sand wrote:
Ruveyn seems to exempt human intervention from "circumstance". Several of the natural forces have time factors that radically change the machinery of evolution. They are not essentially different from other forces but cataclysms such as rapid changes in the chemistry of the atmosphere or the oceans may be too violent for the slower processes involved in evolution to counter for the survival of large numbers of species. There is strong evidence today that such changes are now taking place and major species variations are being irretrievably lost very rapidly. Beyond the loss of any particular species, there are repercussions in associated species and even in the basic chemical complex upon which all life depends. Specialists are aware of this but the bulk of humanity is not only ignorant of the current developing disaster but determinably resistant to recognize it or make the critical adjustments needed to survive. Humanity, for all its vaunted supposed intellect will, in the very near future, discover it is not immune to the results of this vital neglect.


Not at all. The environments the humans create exert Darwinian stresses and pressures on future reproduction. We make an environment as much as an environment makes us.

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psychohist
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02 Jul 2011, 12:24 pm

Does genetic engineering count as a "circumstance"? Does it count as evolution?



ruveyn
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02 Jul 2011, 1:43 pm

psychohist wrote:
Does genetic engineering count as a "circumstance"? Does it count as evolution?


Evolution is descent with modification. If the modification is man made rather than natural it is still descent with modification.

Perhaps the latter phase of human evolution will be more greatly under human control.

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02 Jul 2011, 3:24 pm

psychohist wrote:
Does genetic engineering count as a "circumstance"? Does it count as evolution?

Interesting question. We generally exempt human selective breeding from the term 'evolution,' so GE would be exempt from the term as well; however, if GE genes get into wild populations and are then either weeded out by nature or spread and become fixed, that would be evolution.

For example, pure black canines are a human invention, but back-breeding introduced the gene into wolves and it is now positively selected for in timber wolf populations.



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02 Jul 2011, 3:30 pm

LKL wrote:
psychohist wrote:
Does genetic engineering count as a "circumstance"? Does it count as evolution?

Interesting question. We generally exempt human selective breeding from the term 'evolution,' so GE would be exempt from the term as well; however, if GE genes get into wild populations and are then either weeded out by nature or spread and become fixed, that would be evolution.

For example, pure black canines are a human invention, but back-breeding introduced the gene into wolves and it is now positively selected for in timber wolf populations.


Darwin got his notion of Natural Selection from the work of humans who bred variations of plants and animals from the natural stock. The first few chapters of Origin of Species is all about human selective breeding.

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02 Jul 2011, 3:49 pm

Ruveyn, you are correct, but that has no impact on whether or not selective breeding is considered evolution. Darwin's point was to demonstrate the power of selection, not to equate the two.



ruveyn
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02 Jul 2011, 4:05 pm

LKL wrote:
Ruveyn, you are correct, but that has no impact on whether or not selective breeding is considered evolution. Darwin's point was to demonstrate the power of selection, not to equate the two.


Precisely. Two things are required -- variation and selection. Nature produces variations by the bushel basket. Nature also selections the variant that can survive the current environment. In the not too distant future humans will produce some of the variations AND also do selection of those variants that will be permitted to live. So humans eventually will be able to guide evolution to some degree.

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