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I'm new to this site but had a question on evolution, apologies if some of these questions seem basic but they are from a book i am reading challenging the role of chance in evolution.

Taking the example of Polar bears in the Arctic, how does evolution determine that it was white fur that was a beneficial trait rather than any other colour of fur? Is this a random change in cellular chemistry?

The book argues that there should be more evidence of polar bears of all shapes and sizes but with no evidence, asking "why should the creative factors provide only single options in the polar habitat and let natural selection sit idly by?"

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closed as too broad by Remi.b, rg255, kmm, James, anongoodnurse May 22 '16 at 2:28

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ Your question seems to be based on a profound misunderstanding of evolution, and from your quote you seem to be reading a creationist book that is deliberately misleading you; however, your actual question is unclear. Could you rephrase so we know what you're actually asking? $\endgroup$ – iayork May 13 '16 at 13:55
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    $\begingroup$ First and most important of all: Evolution neither knows nor determines anything. It happens. And if it is not negatively selected, it will occur. $\endgroup$ – Chris May 13 '16 at 14:00
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    $\begingroup$ @Chris I'd hold that last sentence, or clarify what "it" is. $\endgroup$ – Harris May 13 '16 at 14:38
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    $\begingroup$ Welcome to Biology.SE. You said The book argues. What book are you talking about? $\endgroup$ – Remi.b May 13 '16 at 14:45
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    $\begingroup$ @ZainChawdry You won't learn much about evolution from a creationist. However, you might be interested in debunking creationist fake arguments. I would strongly recommend that you start by reading a science book and then when you know what evolution is you can get back to a creationist book if you want to see if what they say about evolution make any sense. $\endgroup$ – Remi.b May 13 '16 at 14:59
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The question is quite unclear but I'll try to say a few words that may help you.

You seem to be considering evolution as an individual that decides what is good and what is not. You seem to be considering the evolution as determing at any time point what will be good for a given species. That sounds very wrong.

Evolution is much more than Natural Selection (NS) but for the purpose of this answer I will talk only about NS. NS is a differential of fitness. Fitness is a function of both the expected reproductive success and expected survival of an individual. The environment is part of what determines the fitness of an individual.

So the question, you might be willing to ask is why is having white fur advantageous for a polar bear. The answer is on this post. In short, polar bear live in a very cold climate and their white fur is actually made of clear tubule which let the sun get through and reach their black skin. If it is unclear for you why dark matter warms up faster than lighter matter, you might want to follow a short physics lecture on light.

I would recommend that you have a look at a very introductory class to evolutionary biology such as Understanding Evolution by UC Berkeley for example. It is pretty short (much shorter than reading the book you're reading and you will learn so much more about evolution).

EDIT

I will not be able to explain you the basics of evolution theory entirely as it would not fit in a single post. So, I am reacting to your first comment but for the follow-up questions, please just have a look at an introductory source of information first and we will all gain lots of time. (No aggressivity here, I just want to avoid spending my day on this single post). Once you've finished an introductory course you are very welcome to ask further questions. Btw, evolutionary biology is a very big field. There are a large number of researchers (me and other users on this website included) who work during their whole to further our understanding of evolutionary processes.

Natural selection must wait for these painstakingly slow changes to provide a large variety of options for it to choose from

This is wrong for two reasons. 1) NS tends to be a relatively fast process for rising the frequency of beneficial mutations. 2) NS does not give options to chose from. It is even the opposite NS remove options to keep only some of them. Mutations create options. In more correct terms, mutation increase the genetic variance while NS (and genetic drift that I haven't talked about yet) remove variation.

A1 allele is a very simple software for students in evolutionary biology that help the to simulate the action of NS and genetic drift on an already polymorphic locus. You might not understand what is meant by "polymorphic locus" but this just mean you need to have a look at an introductory course to evolutionary biology.

if random changes in the cellular chemistry can suddenly alter the colour of hair from black to white, why cannot they change the colour of the hair from black to blue or red or crimson or violet or green, how did cellular chemistry know that what was needed in the arctic climate was only white?

Well, again the hairs aren't really white!

Mutation are random (although this statement can be misleading because there is variation in mutation rate). A mutation is just a "mistake" done during the replication of DNA. An organism does not make mutations to achieve a particular goal. It just make mutations. This is why the vast majority of mutations are deleterious (=decrease the fitness of the individual carrying it).

Now, some mutational effect (in terms of phenotype and not fitness) are more likely than others. For example, a polar bear may already produce a number of pigments that it could "easily" use for colouring its hairs. For example, a polar bear already produces dark pigments (such as melanin) and it is reltaively likely for that a single mutation could darken the fur of the polar bear. If having darker fur was beneficial then this mutation would increase in frequency in the population(assuming no genetic drift which is wrong but this is a story for another time). On the other hand, a polar bear does not produce violet pigments (to my knowledge). As a consequence, it would take a much larger number of mutation (each of which aren't necessarily beneficial) for a population of polar to have a light violet fur (and we would need to assume that having a light violet fur is beneficial).

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  • $\begingroup$ Many thanks for your answer,what do you think of this passage in a creationist book I'm reading-"Natural selection must wait for these painstakingly slow changes to provide a large variety of options for it to choose from. For instance, if random changes in the cellular chemistry can suddenly alter the colour of hair from black to white, why cannot they change the colour of the hair from black to blue or red or crimson or violet or green, how did cellular chemistry know that what was needed in the arctic climate was only white?" $\endgroup$ – Zain Chawdry May 13 '16 at 15:10
  • $\begingroup$ As said in the answer, its actually not white. And, as said by many others, evolution doesn't know anything; its just a matter of chance. Fur color would have also converted to blue/crimson/brown, but since white was more advantageous, so it flourished and took over other colors. Here by colors, I mean the species with that color. $\endgroup$ – another 'Homo sapien' May 13 '16 at 15:26
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    $\begingroup$ @ZainChawdry If this answer addressed your problem, please consider accepting it by clicking on the check mark/tick to the left of the answer, turning it green. This marks the question as resolved to your satisfaction, and awards reputation both to you and the person who answered. $\endgroup$ – MattDMo May 14 '16 at 18:57

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