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Natural selection has been called a tautology because it follows from its definition, and because it has no observable consequences by itself that anyone has ever tested against an alternate theory.  

Natural selection has been called a tautology because it follows from its definition, and because it has no observable consequences by itself that anyone has ever tested against an alternate theory.  

== Variation and Randomness ==

==Variation and Randomness==

Natural selection becomes interesting when there is the possibility of random variation in the duplication of individuals--in other words, when an individual is copied, the copy may be slightly different from the original.  It is important to note that, as stated above, the ''mechanism'' for this variation is not explained or even taken into account by natural selection.  All that matters is that there is ''some'' process that produces variation.  In this case, some of the offspring of an individual will be better (where "better" is defined as "more likely to successfully reproduce"--one can think of it as scoring higher on an evaluation) and some will be worse.  The higher-scoring offspring will soon come to dominate the population, and over successive generations the average score will also rise.

Natural selection becomes interesting when there is the possibility of random variation in the duplication of individuals--in other words, when an individual is copied, the copy may be slightly different from the original.  It is important to note that, as stated above, the ''mechanism'' for this variation is not explained or even taken into account by natural selection.  All that matters is that there is ''some'' process that produces variation.  In this case, some of the offspring of an individual will be better (where "better" is defined as "more likely to successfully reproduce"--one can think of it as scoring higher on an evaluation) and some will be worse.  The higher-scoring offspring will soon come to dominate the population, and over successive generations the average score will also rise.

Natural selection has been used to explain many organism traits. For example, deer run fast because slower deer have been eaten by predators, and the faster deer are more likely to pass their traits to the next generation.  [[Selection pressure]] is seldom so one-sided; for example, the long tail of the [[peacock]] leaves it vulnerable to predators.  However, since peahens are far less likely to mate with short-tailed peacocks, a long tail is an overall advantage and thus is selected for.

Natural selection has been used to explain many organism traits. For example, deer run fast because slower deer have been eaten by predators, and the faster deer are more likely to pass their traits to the next generation.  [[Selection pressure]] is seldom so one-sided; for example, the long tail of the [[peacock]] leaves it vulnerable to predators.  However, since peahens are far less likely to mate with short-tailed peacocks, a long tail is an overall advantage and thus is selected for.

== An Example ==

==An Example==

Here is an example of how an engineer might use an algorithm that is analogous to the combination of mutation and natural selection in the evolution of organisms.

Here is an example of how an engineer might use an algorithm that is analogous to the combination of mutation and natural selection in the evolution of organisms.

Note that this engineer need not be conscious of the overall goal--he is just applying a simple algorithm over and over.  Indeed, the engineer need not be conscious of anything at all--his task could be performed automatically and without sentience or intelligence.  Note also that the final plan may be very different from any of the original plans.

Note that this engineer need not be conscious of the overall goal--he is just applying a simple algorithm over and over.  Indeed, the engineer need not be conscious of anything at all--his task could be performed automatically and without sentience or intelligence.  Note also that the final plan may be very different from any of the original plans.

== Local and Non-Local Improvement ==  

==Local and Non-Local Improvement==  

The above section illustrates how natural selection and random variation can combine to create improved individuals.  However, it is important to note that there is no long-term planning involved in natural selection.  This means that all changes must be locally beneficial in order to survive.  Essentially, no improvement can take place if a deterioration must take place first.  In order for a change to propagate to future "generations" of individuals, it must not be significantly harmful to ''any'' generation.

The above section illustrates how natural selection and random variation can combine to create improved individuals.  However, it is important to note that there is no long-term planning involved in natural selection.  This means that all changes must be locally beneficial in order to survive.  Essentially, no improvement can take place if a deterioration must take place first.  In order for a change to propagate to future "generations" of individuals, it must not be significantly harmful to ''any'' generation.

Again returning to the peacock, it might be an overall advantage to have a very short tail or no tail at all, since predators would be easy to avoid.  However, since a ''slightly'' shorter tail gives little help in avoiding predators and also is much less attractive to females, short tails are unlikely to come about.

Again returning to the peacock, it might be an overall advantage to have a very short tail or no tail at all, since predators would be easy to avoid.  However, since a ''slightly'' shorter tail gives little help in avoiding predators and also is much less attractive to females, short tails are unlikely to come about.

== Natural selection and evolution ==

==Natural selection and evolution==

Natural selection is often considered to be synonymous with [[Theory of evolution|evolution]], but the two ideas are distinct.

Natural selection is often considered to be synonymous with [[Theory of evolution|evolution]], but the two ideas are distinct.

* Mutations can alter the genetic information.

* Mutations can alter the genetic information.

Some of the variations produced by these mechanisms are better suited for given environments than other variations.

Some of the variations produced by these mechanisms are better suited for given environments than other variations.

Natural Selection removes the variations that are unsuited or less suited to those environments, in favour of those more suited ("fitter") to those environments.

Natural Selection removes the variations that are unsuited or less suited to those environments, in favor of those more suited ("fitter") to those environments.

According to evolution, mutations can give rise to new genetic information, thus the offspring can have new capabilities that were not coded in the DNA of their parents, and that Natural Selection will therefore select for these new capabilities if they constitute a survival advantage.

According to evolution, mutations can give rise to new genetic information, thus the offspring can have new capabilities that were not coded in the DNA of their parents, and that Natural Selection will therefore select for these new capabilities if they constitute a survival advantage.

We see that variations only come to already-existing plans (DNA), and that changes to the plans produce nothing new.

We see that variations only come to already-existing plans (DNA), and that changes to the plans produce nothing new.

== References ==

==References==

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