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Great why? s of evolution.

  1. Feb 5, 2006 #1
    Great "why?"s of evolution.

    We know what happened in evolution - about how cells formed, became eukaryotes. then clumped together, became vertebrates (fish,) amphibians and reptiles, who evolved into mammals and birds.
    But... why??? What was the point of coming out of water? What caused these events?
    • Why did a nucleus evolve?
    • Why did cells begin to clump together into multicellular life?
    • If an exoskeleton is for protection against predators, why did an endoskeleton evolve?
    • Why did insects evolve?
    • Why did fish crawl out of water? What was the point?
    • Why did reptiles become mammals?
    • If Homo Sapiens killed the Neanderthals, what happened to Homo Erectus, Australopithecus etc?
    • Why did the dinosaurs evolve?
    • Why did the dinosaurs become birds?
    • What caused the Permian extinction a quarter of a billion years ago, which killed 90% of marine life?
  2. jcsd
  3. Feb 5, 2006 #2


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    Mmm OK. First:
    There is no "why" in evolution. That way lies madness.

    Now, a broad generalized answer to some of your questions:

    Critters are competing over limited resources: food, space, protected areas to breed, etc. Any critter that is able to take advantage of a resource that other critters can't, will prosper. Fish that were able to surive limited periods of out water were able to escape predators, find other types of food (such as land plants), etc. Thus, they flourished.

    Critters who had better control over their body temperatures could hunt, forage and escape better in colder weather. This gave them an advantage, which led to prosperity (mammals more successful than reptiles).
    Last edited: Feb 5, 2006
  4. Feb 5, 2006 #3
    Indeed, "why" is not a question that applies here. It assumes that there is a purpose or a goal when there isn't one. Things change all the time and so do living organisms. Chemical changes are mainly random as molecules bounce around and bind in various ways, producing all sorts or compounds. Most of these combinations lead to nothing in particular. But over millions of years, in billions of minute crevices you can find on a water-rich planet, some of them can result in stable and even self-propagating chemical systems. Stable systems of course tend to persist for long periods of time, spread and continue to combine in other ways. Life quite likely emerged this way through random combinations. It continues to evolve following similar processes, although these processes have become somewhat organized due to the fact that nucleic acids can combine and form unique sequences. But essentially, chance combinations that happen to be stable enough to persist in their environment survive while those that are not perish. There is no other reason.
  5. Feb 6, 2006 #4
    Both posts above should have answered your question,
    I think it is mainly due to fitness enhancement. Environment changes are the main cause .
  6. Feb 7, 2006 #5
    To FeynmanMH42:

    Do not think that "why" questions have no place in understanding organic theory of evolution--this is clearly false. Thus, consider "why" humans share 99 % of their genome with certain species of the great apes. Why indeed ? Do you know any scientific theory other than the theory of evolution that attempts to answer such a "why" type question ? Many other examples of "why" questions asked by those that study the details of evolutionary theory exist. But, as posted above, the types of why questions you ask all have the same answer when approached from the view of organic theory of evolution...e.g., "because the outcomes were adaptive at the time of the events". I also note that you add two "what" type questions--e.g., what caused extinction of this and that. There are numerous hypotheses for such "what" type questions that fit within the framework of the theory of evolution.
  7. Feb 8, 2006 #6


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    As noted above, the general answer to your "why did..." questions is "because it worked". Evolution does not have a preset direction. Variations in species happen. Some variations work better than others in a particular environment/ecosystem.

    If you ask something like "how did the nucleus evolve" instead of "why", then you can have a big discussion.

    Note that exoskeletons are not the ONLY protection against predators. Also note that exoskeletons have trade offs in other areas as compared to endoskeletons (or even no skeletons).

    Kind of the same theme as above...evolution does not progress toward "perfection". Rather, it creates & tests variations. (I don't mean to personify it.)

    Certainly we don't have the whole history of how that happened, but consider things like this: (1) the ability to walk appears to have evolved while the creatures were still aquatic (i.e., fish didn't exit water and then develop the ability to maneuver on land...but once on land the "primitive" legs were able to adapt to new forms) (2) being one of the first land animals, there was lots of open space with no predators, little competition for food, etc. (creatures tend to fill up open ecological niches)

    A branch of the Australopithecines (now extinct) were the ancestors of the branch for the genus Homo. H. erectus (now extinct) was one of the early species in our branch. It appears that H. erectus was the ancester of both H. sapiens and H. neanderthalensis.

    So, an Autralopithecus population split...one branch led the the genus Homo and the other(s) went extinct. The genus Homo started (roughly speaking) with H. habilis...which split into a branch that became H. erectus (other branch(es) went extinct)...which split into a branches that included archaic H. sapiens and H. neanderthalensis (lived at the same time). H. sapiens survived and became modern humans (H. sapiens sapiens) and the Neandertals didn't survive.

    My point is to focus on the branching variation theme of evolution rather than to picture it as a ladder.

    Note: not all did. Just a branch of those that survived the KT event.

    Still a matter of much research from what I understand. Possibly an asteroid impact. Possibly from massive volcanic activity. Try Google.
    Last edited: Feb 8, 2006
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