Unchanged organisms

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Discussion by: aydin
Hello,

It’s a bit embarrassing but I was asked the following question and wasn’t able to give a satisfactory answer;

“Fossil record shows that certain animals that we see today have not changed for hundreds of millions years, animals like crocodiles, sharks and turtles.. How can this be explained by the theory of evolution?”

I know that if the environment remains that same there is no need for an organism to evolve, but some organisms have remained essentially the same for 200 millions years!! Don’t tell me this is not a long time because it is, even on evolutionary process scale. There are certain species that evolve even within our living time frame, couple of hundreds of years and there is a new species or subspecies .. How come a shark hasn’t changed in 200 million years?? Even the chemistry of the oceans must have changed…

I answered by saying that “since their environment hasn’t changed, they didn’t change either”. But I didn’t quite believed what I said..

Thank you in advance!
Aydin

34 COMMENTS

  1. Good question. The truth is that they have changed. The species of sharks, crocodilians, etcetera that you are referring to are not the same species that existed tens of millions of years ago. Yes, there were sharks and crocodilians, but not the same ones. Even the coelacanth so often referred to as a “living fossil” is a different species than its relatives in the fossil record. The environments are, as you mentioned, very similar to those found in the distant past and for that reason the same basic body plans still work. I hope that helps answer your question.

  2. @ aydin OP – It’s a bit embarrassing but I was asked the following question and wasn’t able to give a satisfactory answer;

    “Fossil record shows that certain animals that we see today have not changed for hundreds of millions years, animals like crocodiles, sharks and turtles.. How can this be explained by the theory of evolution?”

    This is misleading creationist nonsense which they love to spout with airs of pseudo-”authority”! The basic body plans have not changed, but the genetics and diversity of species, are not the same, even if the fossil cast in the rock bears a close resemblance to modern species!

    http://en.wikipedia.org/wiki/Crocodilia – Although crocodilians were thought of as living fossils for many years, review of their fossil record in the last decade has shown their snout morphology has been continuously changing throughout evolutionary history.[15]

    Furthermore, snout and skull morphologies seem to be functional adaptations to the selection pressures that crocodilians face from the diet in their environments.[16]

    For instance, long-snouted crocodilians, such as Gavialis gangeticus, that live in habitats where small, rapid, agile fish are the main food source need to be able to move, open, and close their snouts rapidly through the water.[17] Thus, long snouts have evolved in such habitats to benefit from hydrodynamic efficiency, since a long out-lever allows crocodilians to quickly open and close their jaws while in water.[18]

    On the other hand, the need for a strong mandible is crucial for short-snouted crocodilians, such as Alligator mississippiensis, which are found in habitats where large terrestrial vertebrates, amphibians, and fish are the food sources.[16] Thus, these crocodilians have evolved to increase the mechanical strength of their mandibles by developing a larger mass of m. ptergoideus posterior muscles.[18]

    Therefore, natural selection seems to lead to the evolution of an effective crocodilian snout by creating a mechanical compromise between bite force and hydrodynamic efficiency.

    If you look at the sections on “Extant taxonomy”, “Taxonomy”, and “Phylogeny” you will see the diversity of, and within, species, – on which selection has acted, and is, acting.

    You should remember that YE-creationist books, are written by ignorant idiots (who probably don’t know a crocodile from an alligator or a caiman ), and are aimed at a market of fundamentalist biology duffers who believe whatever appeals to their preconceptions!

  3. Chipmunk is correct I believe, they have changed. Compare for instance the Megalodon and the sharks of today (e.g. the Mako), there is quite a substantial size difference as well as various other biological differences. The basic shape is very similar as well as other morphology but not identical. The sharks we see today are not the same as the ones we find fossils of.

  4. Chipmunk gave a great answer, I would just add a couple other thoughts. Its not the entire environment that is significant in this discussion but the specific niche that any organism has in that environment. So if I’m a parasite that lives by eating other parasites that live on sharks a lot can change in my environment and it won’t impact me in the least as long as the same parasites keep living off sharks and as long as the sharks thrive. And on the other hand, organisms can evolve even if their environment stays totally constant, that is the whole point of random mutations, most of them will be counter productive but every once in a while one will be good and even if nothing changes in the environment the good mutation will stick. Of course the more static the environment is, the less likely that new mutations will be useful and vice versa but the main point is there are lots of variables to determine when and how an organism evolves and environment is a very important one but not the only one.

  5. Evolution is not seeking perfection or improvement – it is seeking survival. If a species in its current form continues to thrive and there are no pressures on it to change it may well not change significantly for a very long time.

    At the same time these species that look very similar to their ancient ancestors likely have a myriad small differences that have evolved over the ages to protect against evolving disease, parasites, new predators, etc…

  6. I would be embrassed to answer sense I am not a biologist, but species evolve by biochemical mechanisms and through natural selection (I guess) I bought the book The Growth of Biological Thought (1982), that took 10 years to be written by Ernst Mayr (didn´t finish the reading), he does compare the lifespan of species to a clock. That´s only my suggestion, I am not biologist as I told (but that´s a question that made me once curious about, despite the fact that I am not a biologist). I would defer the question to biologists and try to read this book.

  7. One feature about a good environmental adaptation built up over, thousands or millions of years, is that if a mutation causes a variation, it is likely to be less competitive than the existing form in a stable similar environment. It would then be selected against by environmental influences.

    This is however, unlikely to be so, for ALL the features of an animal, or ALL genetic changes.

  8. I’ve never seen a crocaduck :P. And am amazed how a banana fits into my hand. JK If people are willing to listen to those arguments, it’s an uphill battle you fight. I wish you the best of luck. It’s hard to know all of science, but being confident knowing the earth is about 4.5 billion years old, and life started about 3.5-4 billion years ago is a start. The rest is filler although interesting. Science can be modified and corrected. it’s a great thing. “Problems” with evolution either arise from our personal misunderstanding, or will be corrected by the scientific method. Even if something hadn’t evolved for 200 million years that does not disprove evolution, nor does it equal god. I agree with another poster, I wouldn’t dumb it down but tell it like it is. The crocaduck arguers and listeners wouldn’t listen (yet?) to even a basic explanation. They have their blinders on.

  9. The best defense is a good offense: ask pesky questions to poke holes in their facade of canned answers. You’ll have more fun.

    When god created Adam, he had not thought far enough in advance to realize Adam would be lonely for someone to talk to and hang out with. God the omniscient was not much of a friend or conversationalist. Why did he impose this suffering on his most perfect and innocent creation? If god had not planned on anyone other than Adam, why did he create Adam with a penis and testes when a simple spigot would have sufficed? He must have intended for Adam to masturbate from the get go, but why and about what? Why didn’t the serpent take full advantage of Eve when he had the chance to impregnate her with his devil seed? Why did god create Adam with “seed” that were completely useless by themselves, or seminal fluid to carry them to nonexistent and unplanned for (btw, do vaginas have teeth and if so were they created or did they evolve?) or forbidden places (the ground)?

    God the omnipotent could make Adam from river mud but had to steal a rib from Adam to make Eve. So they would have to have had compatible blood types or the transplant would have failed. Where did the other blood types we have come from and why? If god had not planned ahead and intended original sin, why did he create Eve with ovaries and a uterus? She could have amused Adam just fine without them and there would have been no future demand for condoms, birth control pills or abortions. So god created them with the absolute intention and knowledge that they would break his law out of the very ignorance he gave them? God created man with the intention that he sin, so why punish him for succumbing to god’s intent? The true original sin was god’s not man’s.

    What color eyes, hair and skin did they have? Please explain again about how other people ever got produced if all their progeny were male? The only answer I’ve thought of is that they were offspring of Adam and Eve that were never mentioned for no good reason or the incestuous offspring of Eve and her sons who were never mentioned for obvious reasons. Were the animals in the Garden capable of Original Sin? If not, why were they expelled from the garden, it was hypocritical of god to do so, not just and merciful – or are animals not deserving of just and merciful treatment?

    (The more completely reasonable and explicit questions you ask about sex, the more uncomfortable they’ll get and the sooner they’ll go away. Did Eve ever masturbate before she got around to f-ing Adam? When and where did the first orgasm take place? Did they enjoy oral sex? If they are responsible for all the sins of man, there’s no reason to think that their descendants and therefore the descendants of ALL people, including the prophets and apostles, and their progeny, are the products of incestuous liaisons. How could god’s commandments not prohibit this sin? How can modern christians bear to commit it even if properly married?

    Starting with such an incestuous past and only 6000 years of incestuous couplings (after all, it got repeated after the flood with the small number of humnas Noah had aboard the ark) just think how closely related we all are? All the more reason to marry and reproduce with people who are maximally different from ourselves … particularly racially and religiously (christian x muslim, hindu, buddhist, etc. What’s worse, incest or boffing a non-believer? If they are equally bad, how can your religion even sanction sex within marriage? Even if it does, isn’t that against god’s law? Isn’t it as much an abomination homosexual sex or marriage?

    Everything about about the garden of eden and the creation of man smacks of preplanned, intentional deception, lies, entrapment or total incompetence on god’s part. (1) God set it up because he was a perverse, sadistic psychopath. (2) God was a hopelessly incompetent cowardly f-up who didn’t have the honesty, decency or balls to take responsibility for his own failings. Instead he projected them onto man upon whom he inflicted the cruelest, most unjust punishments for His own failings and outrageous sins. God deserves expulsion from he own paradise to suffer the torments of hell for all eternity. He deserves the same fate he intended for men, women and their children. He condemned man to suffer death and perdition. Man demands god’s justice” an eye for an eye. Leave it to the Son of Man to decide whether god deserves Our mercy, forgiveness and salvation. Accept the obvious truth and justness of this and I wills admit the existence of your god and defend YOUR right to live in self-imposed masochistic submission to his rule, and MY right by free will to reject and oppose such slavery.

    If you can hit them right between the eyes with questions they aren’t quite ready with canned answers to, they might start to wake up … you know, sort of like Zen koans. A few experiences with “Don’t know” mind could be a healthy experience.

  10. My response if asked a question I don’t know the answer to is to say “I don’t know, but I will try and find out for you.” If you don’t know, you don’t know. There is no shame in that. (Hmm, Donald Rumsfeld springs to mind !)

    As other have pointed out there was real change over the 200 million years, even if the body shape is remarkably similar nowadays.

  11. Thank you guys for your answers! (particularly Chipmunk and Alan4discussion). There are some really good ideas in your comments. The example with the parasites was also very interesting!
    Not that the question made me doubt evolution but, I was uncomfortable for not being able to give a satisfactory answer..

    Thank you again!
    Aydin

    • Hi Aydin,

      I am in the position of having studied paleontology at university.

      It is always worth remembering that it is only in the general public where ideas that have no evidence can be freely circulated that the creationist lives. 3 years at university studying geology and there was no need, not even once, to talk about it. Churches and proponents might try and tell the public that the idea is a serious one, or that it is capable of explaining things, but it is very easy to tell people that do not know the answer (or even which questions to ask) that you have an answer. In the world of people who do study the Earth creationism is so low down that it need not even be discussed. For science it is a public relations issue, and only a public relations issue. When you are taught about the world creationist and ID arguments have nothing to add. They exist created by theists only to please theists and have little to no explanatory power.

      We spent an entire term studying shark evolution and the idea that they have not changed for hundreds of millions of years is easily disproved by reference to the fossil record. I don’t remember it now, other than a little on the Neoselachians, which is the branch of the tree that includes the Great White and the Tiger Shark – two of my favorite sharks. The Great White for example generates so much heat from its muscles that it ends up being a little warm blooded, holding its body temperature a bit above the water temperature. This adaptation means it can hunt in slightly colder waters and it is more efficient.

      Apatation in the Neoselachian group has led to increased sensory development and brain size. I can remember that much. It was 10 years ago!

  12. May be worth mentioning one other important little bit: within a certain set of conditons similar sets of efficient exterior body plans develop: hence why dolphins and sharks often have a similar shape, or even marsupial and eutherian mammals filling similar roles (such as marsupial species in australia who look far more similar to rats or anteanters than said species’ close relatives, but are physiologically clearly different). Basically the entire way the animal works physiologically and genetically could be different: there’s no reason why a shark couldn’t gradually evolve to swim around in massive sodium hydroxide concentrations, this would require a very different make-up in the bloodstream (I think, this is a slightly extreme hypothetical), but it would still have a shape that would allow it to swim, and therefore you would not see that much difference in the basic body plan. The outward appearance doesn’t need to change, so it doesn’t, and there’s usually a stabilising pressure on the outward morphology in most respects (example: you’re not going to see the shark spinal column fusing unless you also see big changes elsewhere ie on the fins, since the abilty of the spine to move is vital for its propulsion, any adaption that changes this is selected against unless there’s aother mutation compensating, but due to resource distribution (ie making bigger and more flexible fins costs precious protein) this will also be selected against most of the time. hence different shark species, all looking fairly similar.

    I think everyone else has the subject covered though.

  13. “I know that if the environment remains that same there is no need for an organism to evolve…”

    This isn’t really true, though. Evolution still occurs, since mutations will appear in the genetics of the species and variation among that species will still happen. Once any single or combination of variations proves to confer an advantage over a competing allele (same gene, different types, like hair color), evolution occurs. This is a change in the environment since there are new competitors, true, but I don’t think it’s what you were going for.

    Species that remain morphologically similar for millions or hundreds of millions of years have very stable body plans. They’re like the pyramids of biology. Just like you can’t change the basic shape of a pyramid much before the thing will collapse, you can’t change the shape of a generalist shark much without hindering its survival. You can improve its cardiovascular efficiency, its osmotic regulations, its digestive gut flora, or even its cognitive abilities, but only the body shape remains in fossils, and that is the one thing that for many species can’t easily change without a punishment, which means removal from the gene race.

    Next time you get such a question, ask why we still use spheres for balls. We changed nearly every other thing about this prominent sporting item, but it’s still a sphere. Has the sport never, ever changed? Is it just hard to see the rubber inflation hole in a 500bce Japanese wood carving? I doubt your adversary will claim vinyl was used in Medieval football matches to preserve their point.

    • This is my favorite answer thus far. This and Chipmunks!!!!

      In reply to #15 by NH King:

      “I know that if the environment remains that same there is no need for an organism to evolve…”

      This isn’t really true, though. Evolution still occurs, since mutations will appear in the genetics of the species and variation among that species will still happen. Once any single or combination of variations proves to confer an advantage over a competing allele (same gene, different types, like hair color), evolution occurs. This is a change in the environment since there are new competitors, true, but I don’t think it’s what you were going for.

      Species that remain morphologically similar for millions or hundreds of millions of years have very stable body plans. They’re like the pyramids of biology. Just like you can’t change the basic shape of a pyramid much before the thing will collapse, you can’t change the shape of a generalist shark much without hindering its survival. You can improve its cardiovascular efficiency, its osmotic regulations, its digestive gut flora, or even its cognitive abilities, but only the body shape remains in fossils, and that is the one thing that for many species can’t easily change without a punishment, which means removal from the gene race.

      Next time you get such a question, ask why we still use spheres for balls. We changed nearly every other thing about this prominent sporting item, but it’s still a sphere. Has the sport never, ever changed? Is it just hard to see the rubber inflation hole in a 500bce Japanese wood carving? I doubt your adversary will claim vinyl was used in Medieval football matches to preserve their point.

  14. To understand the question, ask yourself, since bacteria are asexual in reproduction, is it possible that the first bacterium on the planet is still alive?

    Change is a characteristic, but not a necessary one, of evolution.

    • In reply to #16 by JHJEFFERY:

      To understand the question, ask yourself, since bacteria are asexual in reproduction, is it possible that the first bacterium on the planet is still alive?

      If it is, its genes are probably quite different!

      Change is a characteristic, but not a necessary one, of evolution.

      …But then bacteria have short life cycles, and engage in horizontal gene exchange, so are in constant flux!

      Most thinking in genetics has focused upon vertical transfer, -

      • In reply to #19 by Alan4discussion:

        In reply to #16 by JHJEFFERY:

        To understand the question, ask yourself, since bacteria are asexual in reproduction, is it possible that the first bacterium on the planet is still alive?

        If it is, its genes are probably quite different!

        Change is a characteristic, but not a necessary one, of evolution.

        …But then bacteria have short life cycles, and engage in horizontal gene exchange, so are in constant flux!

        Most thinking in genetics has focused upon vertical transfer, -

        but there is a growing awareness that horizontal gene transfer is a highly significant phenomenon and amongst single-celled organisms perhaps the dominant form of genetic transfer. http://en.wikipedia.org/wiki/Horizontal-gene-ransfer

        Of course you’re right, Alan. But even within our lifetimes, our own personal genetic makeup can change. Does that make us a different organism? I just wonder how you define a “life form.” If the original bacterium just changes its genes over time, but never really “dies” is it still alive? It’s just sort of a thought experiment.

        • In reply to #29 by JHJEFFERY:

          Of course you’re right, Alan. But even within our lifetimes, our own personal genetic makeup can change. Does that make us a different organism?

          Our personal phenotype (body form) changes from juvenile to adult and then ages, while some of our DNA degrades. Even our cells die and are regularly replaced by new ones, but our DNA genome does not change significantly. It just has different genes switched on or off – (a bit like an electronic system with time switches).

          I just wonder how you define a “life form.” If the original bacterium just changes its genes over time, but never really “dies” is it still alive? It’s just sort of a thought experiment.

          I think on Earth, we would define life as “self replicating cells or DNA”. The copying is approximate, not perfect, but serious flaws or fatal variations are quickly weeded out at cellular or individual organism level.

          The taxonomy, classifying life forms is also a bit rough and ready. Nature “does not do”, hard species boundaries as evolution progresses onward.

  15. One or two other comments here have asked why it is we have to have all the answers – as in “Well, you can’t explain what happened before Big Bang. Ha!”

    It certainly is annoying but I have no problem in asserting some general scientific fact without personal understanding or having covered the subject to doctorate level! As you have done, aydin, we go away and look up the answers – and that, he says rather smugly, is what separates us from them.

  16. The other interesting thing is that there has been change, as a matter of fact, among their ancestral lineages and cousins. It’s just that the more divergent lineages died out, and the survivors were more like their primitive forebears.

    This is one reason why I dislike the term “living fossils” and prefer Richard Fortey’s term “survivors”.

    In his latest book, paleontologist Richard Fortey cast the tuatara, coelacanth, and similar organisms as “survivors.” This is a more positive spin on their identity. Rather than being left behind by evolution, and therefore aberrations unworthy of our attention, these primitive-looking forms of life can tell us much about the history of life on earth and the mechanics of evolution. And there certainly is a phenomenon worth investigating here. “Living fossil” is awful because it’s an inaccurate term that doesn’t do justice to the lineages the label is applied to, but why certain forms have persisted for so long is something worth puzzling about.

  17. I hate being late to such a well written thread. So many great posts. I’d just like to add that overt phenotypic changes may not have occurred. Therefore, the overall appearance may stay the same. But, genetic changes have accumulated.

    Scientists are able to arrange these changes chronologically and demonstrate the genetic changes that underpin the species development and change over the course of history.

    I loved reading this thread. YAY evolution!!!!!

    • In reply to #23 by jimbobjim:

      I thought YEC believed in “micro-evolution”?

      Ah! Micro-evolution!! We discussed that recently! – http://www.richarddawkins.net/discussions/2013/1/31/macro-evolution# “Micro-evolution” is just ordinary evolution looked at in the short term, but YECs try to pretend it is something different.

      I have encountered many versions of YEC ignorance! This is because there are no particular constraints on the diversity of fantasies based on wishful thinking or the various levels of incredulity!

      There are similarities where they copy stuff from YEC books or YEC websites, but there is no overall tested view as there is in scientific theories or reputable studies.

      YEC views are wandering in the shifting sands of denial.

  18. Evolution: Self-replication+heredity+variation+natural selection=design out of chaos without the need for mind.

    When things replicate, their ability to do so without variation is called fidelity. If there is low fidelity, genes mutate to a point of dysfunction and have no progeny. If there is too high of fidelity there is no variation and so no change. As genes evolved they found a stabilizing point to allow for a certain degree of error, as it was beneficial (enabled survival). Some species have more fidelity than others. Also, in the case of a animals like sharks, I think your environment answer was false but had some truth to it. Sharks developed such dominating traits that changes in the environment did not amount to selection pressure.

  19. The gene pool of a population tends to change slowly and in a conservative manner (except many that undergo punctuated equilibrium). Although the oceans have changed over the last 200 million years, the changes are not sufficient to cause dramatic changes that are easily identified as adaptive evolution. With respect to body form and skeletal structure, oceans have changed very little, if any. What evidence have you that there have been absolutely NO changes in sharks? There can be subtle yet adaptive changes in their physiology that are not seen in fossil remains. By the way, there are a few organisms that are relatively unchanged much longer than sharks such as Horseshoe Crabs, Lobe-finned Fishes (Latimera), and brachiopods. Latimeria dates back some 400 million years and brachiopods are living fossils that date back 1.5 million years (the Ordovician Period). It may be impossible to know if there have been physiological changes during that long period of time.

  20. Even in the absence of environmental changes driving selection, populations will often undergo genetic drift where they begin to change just by the slow accumulation of harmless genetic mutations. If the environment selects against drift, however, then the organisms will continuously be forced into the narrow genetic makeup of their ancestors. Think of an environment like a valley, where the genetic makeup of a population tends to rest at the lowest part of the valley. If the environment changes and the valley uplifts, the population’s genetics can be “forced” (selected) out of the valley, over the hills and down into the next valley – occupying a new niche and perhaps becoming a distinct species. If there is no forcing, but the valley is broad and its slopes shallow, the genetic makeup can drift and spread out across the valley, and some few might even chance to escape over the low hills and form a new species. If the valley is deep and the slopes are sheer walls – the environment selects against changes – then the genetic makeup will stay isolated and unmoving for even millions of years, even if some forcing comes along and tries to force it out, it will have to resist or go extinct. The fact of the sharks continued existence shows they are the line that succeeded in resisting being out-competed while still being unable to successfully diverge enough to noticeably evolve.

  21. Excellent and well thought out responses. Since evolution rewards the species that are best able to adapt and survive, it makes sense that crocs and sharks are still around, albeit slightly changed from their earliest ancestors. After all, they are some of the worlds’ most bad-ass predators! What species (besides man) hunts crocs and sharks for food?

  22. Just look at the hammerhead shark and ask yourself how long it would have taken for its head to slowly evolve into its present shape after multiple generations of minor mutations, with 99.99% of those mutations being unfavourable ones.

  23. Perhaps an add on for Chipmunk’s answer is that even though they have changed, change being a very broad term, they have been so well adapted for their environment that they have had no need for significant adaptations.

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