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Are the evolutionary changes we seen in creatures occur with a purpose? or is it just due to random changes over millions of years?

It just came to me that evolution seems to be purposeful... meaning it seems to me that an organism changes/evolves almost(!) as if because it "wants" to change. In previous conversations we were talking about evolution happening as a series of mutations that results in benefit to the organism and that organism passing on that change to the succeeding generations. But lets take a look at these "mutations".. if these are just random changes then how did "random" changes push some sea creatures to generate anatomic structures to enable it to survive on land? Fins are said to have developed into feet/legs. Can random mutations actually develop that? to me these seem to be mutations with a direct purpose FOR the organism...that is to develop legs... if that is the result then can it actually develop from a random mutation? or lets take it in another way.. why did the wolf like creature that eventually developed into whales loose their hind legs? did random mutation just shut down those genes for leg development? Some say its because of disuse and eventually the whales lost them. But if its simple disuse, i would expect whales to STILL be born with legs that gradually atrophies as it grown older. But instead a whale is born without legs at all (at least with bone remnants)... to me this is like evolution is intentionally shutting down a system. If evolution is shutting down a locomotion system for the animal can that be a random occurrence? I find random mutation hard to achieve this kind of changes.
Can random mutation over millions of years actually drive the changes we see in animals including man. Or is there something more amazing happening with evolution... creatures developing something unique because it actually wants to evolve that way.... (i hope that made sense). Random? or somehow with some kind of "purpose"?

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  • Jul 2 2013: Thanks george. Religion has no part in my question. Im more curious as to the exact evolutionary mechanisms that happens. I do understand natural selection and it is accepted in my system. Im just looking at it in a slightly "deeper" point of view. More like trying to think of a possible explanation without resorting to books. Im trying to speculate and learn at the same time.

    I was just wondering how small a beneficial mutation can actually occur such that it gains access to the population pool? (did that make sense?)... going back to the fish that evolutionarily sprouted legs... I would accept that millions of year of small beneficial genetic changes did the trick of transformation (over millions of years that would be huge change). But how small a genetic change would that be? Would such a small genetic change in leg development actually enhance the survival of a small lucky individual? I would probably think that a small mutation of benefit would NOT exhibit itself phenotypically much. And if it doesn't express phenotypically enough how would that translate to increased chances of survival? in which case that small benefit would probably be pushed out by the "unlucky" species without such a change by sheer numbers...

    Unless if another scenario would happen... that mutation is driven by somewhat big genetic events in an individual (only ONE individual) that is immediately expressed and definitely gives a bigger advantage and one that is spread by dominant genes. Say a small 1cm fish that suddenly developed a mutation that gives its jaws an added 2mm increase. If that gene were to spread to its offspring it has to be expressed immediately in its progeny to give its children a good start in spreading this trait.
    but if this is the scenario... here's my question.. what in the natural world would give a 1cm fish the mutation benefit of an added 2mm increase in jaw girth? random changes?.. that is one very very lucky fish!
    • Jul 3 2013: I think you are getting it backwards, the process works the opposite way. There are two wrong assumptions you are making: 1) all mutations are either beneficial or detrimental to the individual, and: 2) all mutations manifest themselves immediately so the individual is forced to succeed or fail right away.

      There are mutations that are neither beneficial nor detrimental for the individual, those mutation tend to spread among the population, just accumulating in the genetic aquis of the species, waiting for an external event to trigger them. On the other hand, a mutation not necessarily manifests itself immediately it might remain hidden for generations and only express itself when a change in the environment triggers it, making it look as if the whole population automatically evolved spontaneously to to respond to that change, however the fact is that natural selection simply wiped out those who didn't have the mutation. Look at the ants, is a well known fact that if you expose them repeatedly and steadily to the same poison they will develop resistance to that poison, but the trick they do is that even when they all come from the same mother, they have their own genetic aquis which makes all individuals slightly different, so when you poison them what you really do is to manipulate natural selection to kill all those for whom the poison is more toxic and let alive those for whom the poison is less toxic, that way only those who have better resistance to the poison survive, if you repeat the process again and again, one day all of them become resistant, but the price they pay is that their genetic aquis is diminished and because of that they (as a population) become less resistant to other poisons. Consider also this: if all mutations would manifest immediately, all individuals with detrimental mutations would die before reproduction, but that is not always true and the proof of that are genetic diseases.

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