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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 3 2013: "Are the evolutionary changes we seen in creatures occur with a purpose? or is it just due to random changes over millions of years?"

    The answer is neither.

    Those changes are mostly the result of random variation (due to random mutations), natural selection (positive and negative selection), and semirandom drift. But not purely random changes. I see no reason to think that they are purposeful. For that to happen a mechanism for directing changes would have to have evolved in some organisms. So far, only humans seem to be on their way to directing their own evolution.
    • Jul 3 2013: Entropy.. thanks. But its still a bit confusing. Lets put the question into my frame of idea... its kinda simplistic so please help me understand. Very few of the sites on evolution seem to tackle my problem. Feel free to correct my questioning because i might be assuming a wrong idea in my question.

      This is my question: Lets presume there are no moving animals on land and only fish exist and in water (naturally).. then over mllions of years... fish somehow used fins for locomotion on land and developed the capacity to survive longer on land but still had to return to water.. then over millions of years again, those fins developed into a rudimentary leg (or equivalent) and developed the ability to breath air without returning to water.
      Ok this is the question:
      1. Would you agree the change from a water creature to something can live on land is evolution (by any mechanisms) in action?
      2. You mentioned that these changes are due to random variation(random mutation)... if these changes are random... how is it that "random" mutations are enabling the development of a limb for land movement or lungs that can resist drying? --i am lost as to what mechanisms could have happened in between that seems to make evolution seems soo directed.

      I understand examples on different colored beetles survival , antibiotic resistance etc,what i am curious about the development of organs for a different function which seems to be absent in most of my readings:

      3. for example: Cetaceans were said to originate from hoofed mammals..Dolphins developing sonar is a mystery to me. I don't suppose those hoofed mammals have sonar capabilities? Lets assume they don't. But what kind of random mutation could have pushed dolphins to develop sonar detecting capabilities?
      If those hoofed animals have sonar capabilities then that capacity evolving into the present dolphins, i would understand that scenario. But the development of a new sense "organ"? If by random mutation its kinda hard to swallow
      • Jul 3 2013: "i am lost as to what mechanisms could have happened in between that seems to make evolution seems soo directed"

        But you keep forgetting selection. You seem too fixated on the random nature of mutations and forget that no matter how random mutations are, survival is not random. That survival filters out crappy mutations and leaves inconsequential, semi-inconsequential, and advantageous mutations.

        In your example of fish going into land, some fish have, for example, that "inflatable" floating thing (I don't remember the name, but many fish have that thing). Now, all it takes is variability (semi-random--"semi" because they still have to do what they originally do) for those floating things to vary in how permeable they are to atmospheric oxygen. Now, if a population of these fish lives close to coastal areas, those whose floating things take enough oxygen might survive better if stuck into some shallow waters left after a tide goes low. Several such events might increase the number of fish with floating things that work somewhat like a lung. Such increase in proportions will increase the probability that semi-lung-ed fish will mate with other semi-lung-ed fish, increasing the mixing of mutations that make those floating thingies work like lungs. Such recombination and further mutations increase lung-like variability ...

        See? You are missing a very important process: survival is not random. Background mutations might be, but survival is not.

        I am pretty sure that textbooks are not silent in this matter Jeff.
        • Jul 4 2013: Entrophy, i think its called an air bladder... i just googled it.. swim bladder.. you are correct. i am fixated on random mutation and not on natural selection as a driving force for change which is why i asked you to correct my question since it may not reflect a correct idea.
          So, if i were to take your example to my point of view, here is the thing: i find it amazing that random mutations can bring about improvement in the swim bladder over the course of time. and with natural selection, its almost as if only those with the best bladders will survive. The natural selection is easier for me to understand... but random mutations bring out the best in swim bladders..? find it strange and amazing. However i am aware that even single nucleotide changes may be enough to bring about a large effect in an organism.
          Therefore I think my the answer to my problem now is rooted in evolutionary genetics since i think my question is focused on how these random mutations spread to the population in question.
      • Jul 4 2013: "i think my question is focused on how these random mutations spread to the population in question."

        It's not really spreading, it's more like each generation those with the best mutations breed with each other while those without those advantages don't succeed as much at reproducing. This gives the appearance of "spreading," but it's more differential in survival and reproductive success.

        See ya.

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