Does evolution happen by chance?

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mentari (March 31, 2009, 11:47:28 AM):
I hope this is not a stupid question because many people say that me being YEC fundamentalist Christian is actually not very bright. So perhaps somebody can help me out:

Does evolution happen by chance ?
Mefiante (March 31, 2009, 13:29:36 PM):
Does evolution happen by chance ?
You need to be considerably more specific about what exactly you mean with “by chance.” If you mean, for example, that somewhere a lizard suddenly grows a beak, some feathers and a pair of wings, and thus “by chance” turns into a bird, then that is a creationist straw man, and a very silly one at that. In fact, if such a thing were to be observed, it would refute evolution.

Strictly speaking, evolution is the study of gene and allele frequencies. This means that evolution concerns itself with how certain genes (or alleles) become abundant or scarce, and the factors that play a role.

Evolution has two main drivers. First, there is “a source of diverse raw genetic material” carried by the totality of organisms belonging to a particular species. Second, there is the collection of environmental factors that determine which of those organisms are more suited to their living conditions and are better able to produce offspring. The better-adapted ones will survive and procreate preferentially, and so their genes will become (relatively) more abundant, while the less successful ones will tend to become scarcer.

It should be noted that the process is statistical, not strictly deterministic: any one poorly adapted specimen could outlive and outbreed any one well-adapted one but, overall, the well-adapted ones will outlive and outbreed the less well-adapted ones. This part of evolution is what is called “natural selection.”

The “raw genetic material” mentioned earlier varies among all the individual organisms of a species. This variation has an element of chance (or randomness) to it insofar as specific genetic differences between individuals are for all intents and purposes unpredictable. The genetic makeup of a specific organism is largely determined by that of its progenitors (parental line) but not entirely. Copy errors and mutations are chance occurrences that keep feeding (and possibly extending) the range of genetic diversity, which the environment then filters for suitability.

Many such variations are largely neutral in terms of their effect on survivability. By pure chance, some genes will be more and some less abundant from generation to generation, just as you are unlikely to find exactly the same number of heads and tails in a long series of tosses of a fair coin. This accounts for so-called “genetic drift” where the genome of a population changes over time. However, sometimes a sudden change in the environment (which, again, for all practical purposes is a random event) can make one of these variants more successful than the others and so ensure its proliferation.

Therefore, the answer to the question is that, while evolution has some elements of chance to it, it does not produce haphazard results basically because less suitable variations are soon eliminated.

'Luthon64
bluegray (March 31, 2009, 17:25:15 PM):
To that excellent answer, I can only add this link: http://en.wikipedia.org/wiki/Weasel_program ;)
And maybe another short summary: Variation in genes is random, natural selection is not.
mentari (March 31, 2009, 20:50:39 PM):
You need to be considerably more specific about what exactly you mean with “by chance.” If you mean, for example, that somewhere a lizard suddenly grows a beak, some feathers and a pair of wings, and thus “by chance” turns into a bird, then that is a creationist straw man, and a very silly one at that. In fact, if such a thing were to be observed, it would refute evolution.

Depends what you define as "evolution". I understand it to mean the transmutation of species.
scienceteacheragain (March 31, 2009, 20:58:27 PM):
There is no need to add to Luthon's excellent description :)
However, I would like to point out a discrepency between the title of this post and the description. The most simple answer to the question: "Does evolution happen by chance" is no, but it does not follow that it is "directed" either. There is no dichotomy there, not even a false one.

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