Is evolution dictated entirely by circumstance?

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What other factors prompt changes in a species?

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.

Why do you mean by circumstance?

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".

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.

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.

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".

No visible clarification yet.

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

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.