Fitness and the Future of Mutation in Evolution

Evolution is one of nature’s constants. It is a force that is always there, acting on all living creatures even though it has no predetermined end. However, over the past 25 years, scientist Richard Lenski believes he has found a model to predict the result of mutation evolution on living creatures over time.  In the article “The Man Who Bottled Evolution,” Elizabeth Pennisi examines Lenski’s work and reports on his findings on the trends of mutation and evolution.

Since 1988, Richard Lenski has been conducting an experiment in which he monitors bacteria’s reaction to the introduction of harsh conditions. Lenski has been introducing stress factors like starvation to a population of bacteria, like E. coli. The bacteria would then be given two options: they would either have to adapt or die off. After about every 500 generations of bacteria, Lenski would freeze a sample in order to use in future research, where he would pit each of the generations against each other.

According to the article, Lenski compared each sample against each other and came to the conclusion that newer generations were more fit than their predecessors. However, even though all of the generations did evolve over time, Lenski noticed a trend: older generations evolved more than newer generations. Lenski explained that the evolution of the bacteria over time is eventually reaches a fitness peak where it has adapted to its environment and will only see minimal evolution.

Out of the original strains of bacteria, only half, or six out of twelve, experienced genetic mutation. Those that experienced genetic mutation while adapting to their environment saw their mutated genes result in an exponentially greater number of mutated genes, allowing them to survive. This experiment shows that evolution is reproducible and is evident in every living creature.

Pennisi made a strong case for the research that Lenski has conducted. By including specific numbers and results from the experiment, Pennisi appealed to logos. In doing so, he strengthened the claim Lenski was trying to make through the result of his experiment. Also, by writing for the respected  science journal “Science,” published by the American Association for the Advancement of Science, she appealed to ethos.

Additionally, Lenski strengthens the research Pennisi reports on through the credibility he brings. As stated in the story, Lenski is a member of the National Academy of Sciences, where he has served on numerous committees. He has also been a MacArthur Fellow, which is an award granted for those that show the potential for creative work across all disciplines. Being a part of both of these prestigious institutions gives credibility to the data from the experiment that is presented.

Moreover, Pennisi included all the findings from the experiment. She did not pick and choose what she wanted to include in her article. Pennisi also kept her emotion and opinion out of the article. This led to a well-rounded and non-biased article.

Overall, Pennisi effectively presented the information and provided an interesting and factual article in doing so. Knowing that her intended audience would most likely be familiar with the concepts of evolution, she did a great job only including what was necessary. Additionally, his appeal to logos and ethos help reassure the reader that what they are reading is accurate.

Looking forward, we have to begin thinking about how this affects us in our everyday lives, especially when it comes to our health. Do you think that there will ever come a time when bacteria will not be able to “outevolve” the vaccines we use to fight them? If not, how will humans be able to defend themselves against disease without effective vaccines? Will our systems evolve over time where we come to a point that we are immune from new bacteria?

For a less science intensive read on the background of the experiment, read:

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17 Responses to Fitness and the Future of Mutation in Evolution

  1. secondcitytocapitalcity says:

    I think that we are trapped in a cycle with bacteria. We created medicines to combat the disease, and in response the bacteria evolves to get around it. This is complicated further with things like antibiotics, which replace the bodies own defense mechanisms. Some people don’t take antibiotics because they don’t want it to hurt the bodies natural defense.
    I also think that it is interesting that the article claimed that “only” half of the bacteria mutated. I think that any bacteria that can genetically evolve that quickly should be considered. For example, it seems like every couple of years, there is a new mutation of the flu or another disease.

    • jps591 says:

      I tend to agree with you. I think it is a never ending cycle as well. Humans are a reactive, not proactive species and vaccines always come in response to an outbreak. How are humans supposed to predict the strain of bacteria that will lead to death twenty years down the road? That being said, I think we will always be susceptible to bacteria and disease. However, we as a species can control the effect it has on our population.

  2. freddie1994 says:

    I agree completely with secondcitytocapitalcity, this is a cycle that is unlikely to end in the near future, if at all. We have to use medicine to combat some infections, but the bacteria mutates and evolves to resist, nothing is going to change that.
    In relation to Lenski saying that, in his study, the bacteria reached its fitness peak, and would only experience minimal evolution, I’m curious as to whether or not the bacteria would evolve drastically if it was exposed to an environmental factor that no one has considered, after all if environments don’t change there is no reason for organisms to evolve.

    • jps591 says:

      That’s an interesting way to think about it. I suppose if things drastically changed bacteria would either have to evolve to stay alive or die off. However, the environment remains pretty consistent on Earth for thousands of years at a time. What kind of alternative environmental factors did you have in mind?

      • freddie1994 says:

        Very very sudden changes in temperature or the introduction of something to the environment that would be highly unlikely to occur naturally. Possibly even the introduction of new predatory species. It would most likely be human caused.

  3. sm1414 says:

    I would agree with freddie1994 and secondcitytocapitalcity about bacteria adapting to medications that humans use to treat the diseases that the bacteria cause. The cycle of living organisms adapting to their new reality and environment will not change. It is what living things do. To quote my exhibit source Jurassic Park, “Life finds a way!” No matter how much we try to prevent bacteria from adapting to our drugs, we will never be able to ensure that our antibiotics and other drugs work. However, I think an important aspect of this debate to consider is the fact that doctors over-medicate in our country. There is no reason why a doctor prescribes antibiotics every time someone comes to their office with the sniffles. In the United States, people want instant relief from illnesses and insist that doctors write a prescription for them every time they go to the doctor’s office. This insistence is part of the reason that the bacteria are able to mutate so quickly; their environment has changed so rapidly that the only way for them to survive is to adapt and resist the antibiotics. That being said, I think as our technology advances, we will find new ways to treat bacterial diseases, so the epidemic caused by antibiotic-resistant bacteria that is feared by many will be easily cured.

    I also find what the article says about the more rapid evolution of older generations interesting. I think this is only logical though because the newer generations have been able to adapt over time, so the changes in their environment are smaller when compared with the other bacteria that have been frozen in time and have not adapted to smaller changes in the environment. Therefore, the older bacteria must adapt more quickly in order to ensure that they survive in their new environment. This evolutionary change also seems like it is more drastic because the older bacteria is adapting to more changes in a shorter time than the newer generations.

    • jps591 says:

      I find your comment about overmedicating in the United States intriguing. I agree with you that people go to the doctor for every little thing, even if it is something their body could naturally fight off. Even though medicine helps us in the short term by relieving our symptoms, it strengthens the bacteria in the long term and helps them stay immune to different medicines. Do you think we can find a medicine that is so potent that it is too much for bacteria to adapt to, leaving the only option for them to die?

  4. running95 says:

    I agree and disagree with sm1414. I agree with him on the point he and the two responders before him make about the cyclical relationship between bacteria and humans. However, I disagree on the notion that doctors overmedicate. Firstly, the idea that as humans create vaccines and antibiotics to combat bacteria and viruses, those organisms evolve to survive, is extremely important to note. Yes, bacteria and viruses will evolve, but no, there will never come a time at which they will become completely immune to all of our treatment methods. To answer jps591’s question, bacteria will never be able to “outevolve” human efforts to fight them. Evolution is exponential and therefore it will never cease–regardless of the age of the species–as long as the environment continues to change. That fact is the reason why although we are not absolutely incapable of evolving we haven’t nor will we until our overall environment changes. For example, humans still have numerous vestigial body parts that are completely unnecessary to our survival today on earth. However, the likelihood of babies being born without a pinky toe, or a third eyelid, or an appendix, or body hair, etc. is extremely low because there is no advantage to losing those parts or regaining use of those parts. Moreover, many genetic disorders that are hereditary will not evolve out of existence because modern medicine makes it possible for those genes to be carried long enough to be passed down through reproduction. However, if one day suddenly our entire environment drastically changed, we would be forced to change with it. And the same concept apples to bacteria and viruses. As long as their environments do not change, they will not change either, however, once it begins to change evolutionary changes (even minimal changes) will begin to be observed.

    That idea prompts my disagreement with sm1414 about doctors overmedicating. Regardless of whether or not doctors overmedicate the vaccines and antibiotics will still be effective as long as they keep up with the bacteria and viruses. In this sense I suppose sm1414 does have a valid point. If doctors are constantly providing antibiotics and vaccinations for everything,disease-casuing organisms will evolve more rapidly and differently in every situation, leading to many many different strains, types and species of bacteria that our medicine may or may not be able to keep up with which will then end in humans losing the battle against disease. At the same time, however, I do not believe that doctors overmedicate. Many of the medicine we have today is crucial to fighting illness and doctors know that and therefore prescribe antibiotics to their patients and suggest vaccinations as well not only to protect the patients but also those people with whom the patients interact.

    • jps591 says:

      I agree with you that antibiotics will always be effective as they accomplish their goal. I think sm1414 and I are looking at it in terms of efficiency. If we constantly have to change the way to fight bacteria, we’re not being as efficient as possible as we constantly have to devote time and energy towards it.

      Your response to my question posed at the end of the post was thorough and I agree with a lot of your points. You argue that things won’t evolve unless there is a reason for them to or if there is a change in the environment. What kind of change in the environment would warrant, for example, the elimination of the appendix in the human body? And, what do you think would be the transition process between having an appendix and having no appendix? Would it become exponentially smaller as generations are born or would it slowly be absorbed by another organ?

  5. phishmonkees says:

    I believe one aspect key to Richard Lenski’s findings that was not thoroughly addressed is that over generations E. coli was able to evolve to find new food sources. Before, the bacteria were mainly reliant on glucose and some of the new cultures “evolved the ability to use citrate.” I believe bacteria will out-evolve the current form of vaccine based on the theory that some bacteria can survive, therefore becoming resistant to vaccines. However, just as the bacteria evolve, so would the vaccine, which would therefore offset the advance of the bacteria. For example, a vaccine that simply kills the glucose, which starves the E. coli of nutrients, would be effective against the first generations. Yet, the more evolved E. coli becomes, we may need a vaccine that not only starves the bacteria of glucose, but also citrate. Newer generations are more fit than the ones that came before, yet interesting enough is that the older generations of bacteria evolved more than the newer generations. Evolution allows for the development of a species into a more complex form, a never-ending cycle. As the article says, “this experiment shows that evolution is reproducible and is evident in every living creature”. This is shown in this article with the advancement of the bacteria E. coli.

  6. nicolina1215 says:

    As sm1414 said, living bacteria and creatures will always do as much as possible to survive and multiply. Human medications will never be able to anticipate the exact antibiotic to kill off an entire species of bacteria because the bacteria that is multiplying will always multiply faster than we can understand what it’s new weakness is. This is one reason why the flu shot needs to change every year, because new bacteria will adapt to previous medicines and produce new viruses. Another example is pest control. A common issue with pest control is that pests constantly evolve and adapt to current pesticides much faster than we can create new ones. With current technology, we cannot predict antibiotics fast enough to prevent an outspread. Generally, the antibiotic is created after the bacteria has spread, and had time to start adapting. Though luckily in the future with more advanced technology, the chance of humans driving out more species of dangerous bacteria for good (before they have the chance to evolve) is likely.

    As jps591 said in his response to sm1414, United States medical providers are prone to overmedication. Though I believe the bigger problem is public ignorance on how to correctly and effectively take antibiotics prescriptions. Many people misconstrue antibiotics as over the counter headache medicine that should only be taken when symptoms flare up. As an article from Understanding Evolution states, “recognizing bacteria as evolving entities and understanding their evolution should help us to control that evolution, allowing us to prolong the useful lifespan of antibiotics” ( Some of their suggestions for effective antibiotic use include taking medication at a high dosage over a short period of time, taking all pills prescribed, not taking unnecessary antibiotics that increase resistance to your immunity system, and only taking antibiotics for bacterial infections. If these helpful strategies were more publicized to the general public, perhaps we wouldn’t need better technology to prevent resistance immediately. Hopefully these tactics will become more popular, allowing people to take control of their own futures and decrease their chances of contracting as many evolved bacterial infections in the future.

  7. foldervral says:

    I agree with secondcitytocapitalcity when he says we are trapped in a cycle with bacteria. the main issue is in evolution there are two options, get stronger or get smarter. Humans have taken the smarter option leaving our natural bodies in the dust an unable to catch up with modern medicine. This means that if ever bacteria were to evolve to a point that our minds cannot keep up with the physical evolution than we would loose the fight and succumb to disease. The face that evolution was enhanced by the severe surroundings makes an argument for how humans as a whole have shielded ourselves from an intense environment thus the need for visits to a gym. The lack of physical stimuli could end up in a devolution of humanities physical capabilities. An example of this would be the lack of a tail that humans now have. While this may not be devolution the loss of this appendage is associated with the lack of use and the new postures that humans have assumed. There is almost no way to be completely immune to a bacteria and all of its future forms unless the vaccine itself or the human body learns to evolve in response to this bacteria faster than the bacteria evolves.

  8. Sl1017 says:

    So much time and energy has gone into research on bacteria, for good reason. I had a biology teacher say that bacteria is debatably smarter than us. They can survive under any conditions because of evolution and are everywhere. Their ability to survive extreme conditions and the fact that we don’t really understand the complexities of their systems yet makes them a valid threat.
    Secondcitytocapitalcity has a very valid point that this cycle will be never ending between the advancement of our medicine and advancements in antibiotics then in return the evolution of bacteria. While bacteria is both good and bad, the bad bacteria that is causing severe illnesses and environmental threats that in turn affect us need to be researched and delt with. I am amazed that this expirement has been going on for 25 years now and will continue to teach us more about the evolution of bacteria. It is expiraments like these that will give us the tools to overpower the bad bacteria eventually.

  9. lnzgirl says:

    I agree with phishmonkees and others that vaccines will evolved just as bacteria evolves to become resistant to past vaccines. I think that its highly unlikely that we will encounter such devastating outbreaks of a disease that will kill off a major part of the population (such as the Black Plague or Smallpox) again because science has information about bacteria and its structural components that it did not have in the past. Each year a new strain of flu comes out and scientists are equipped with a vaccine to stop it because the structural differences are easy to mimic and adjust to.

    On a completely different note, I thought it was fascinating that the earlier generations of the bacteria noted in the original article evolved more quickly and dramatically then its successors. As jps591 mentioned, this trend showed that bacteria was reaching an evolutionary peak from which future mutations were beneficial. I wonder if this idea can be applied to humans. I think that some people would argue that humans are nearing their evolutionary peak, dancing back and forth with various mutations around some ideal form. The next predicted evolutionary marker for humans is the loss of the pinkie toe. I don’t see this as a great improvement to our ability to thrive in our environment. I think that this idea of reaching an evolutionary peak makes some sense in both human and bacterial evolution because there haven’t been any major environmental stressors that have prompted our need to evolve dramatically. In the future, this pattern may change if environmental conditions call for different adaptations.

  10. johnd0pe says:

    I see how it would make sense for a population to reach a sort of limit or asymptote in its evolution. Certainly a species cannot evolve and mutate at the same rate indefinitely, as it would gradually become nearer and nearer to a preferable set of characteristics, at which point, extreme mutations would only land it further from its target physical form. Of course this “target” is only constant if the population’s environment is constant.

    In the real world, the environment is never constant, though it goes through periods of greater and lesser change. When faced with an extreme environmental change, a species is bound to adapt at a very rapid pace; their survival depends on it. But once it’s reached a decent, livable state of adaptation, in which its survival is no longer in imminent danger, the need for adaptation is lessened, so changes aren’t required to come as quickly. I would expect to observe this proportionality between rate of evolution and necessity to adapt.

    A very interesting demonstration of this same trend which Lenski found can be seen in this computer simulation, Here, evolution is simulated through a program which generates different forms of geometric “cars” of various shapes and sizes which drive down a track full of hills, bumps and cliffs. Initially randomly, one car at a time is generated and the successful ones are used as a basis for later generations. At first, the changes between generations are fairly drastic as the preferred design is discovered, but eventually each generation begins to look very similar to the one before it. The best design for that specific track is eventually converged upon, so changes are minimal after a long enough time. However, a car that is ideal for one track is not necessarily fit for another track. So if you take an ideal design and try it out on one of the other tracks, it will again begin evolving very quickly until reaching a design best fit for the new track.

  11. drc1995 says:

    I too, like many of you, also agree with secondcitytocapitalcity’s assessment that we are locked in a vicious cycle with bacteria. Since I went to a school originally focused on studying veterinary science, I think I might be able to share one example that some people might not have heard of that stretches outside just the realm of bacteria. This cycle can also be extended to ticks/ fleas.

    Frontline Plus, one of the main topical treatments for tick and flea control is also in the middle of the cycle of becoming outdated due to population of fleas and ticks slowly becoming resistant to it. There are some other outlying factors like owners and vets not being attentive enough to applying this medication, waiting until after fleas and ticks are already infesting a dog or cat, or some other issues, but an overall trend seems to suggest that these insects are evolving. This evolution, in a sense, is an evolution of the ability to resist some of the key ingredients called fipronil. Slowly but surely, some vets are starting to switch to other medications that are slightly modified or comprise entirely new ingrediants to provide a more secure resistance against ticks and fleas themselves.

    Responding to jps591’s questions, I quite honestly don’t think that some time in the future, bacteria will be able to be “out evolve” the vaccines that humans create. There will always be one small little correction we can make to a vaccine to modify it so that it can can potentially combat a type of newly evolved form of bacteria, and there is always the possibility of coming up with entirely new medications and made up of new key compounds. The question I think is, with all the possibilities of evolution that something like bacteria can go through, will we be able to make a vaccine in time to effectively deal with it if it become too dangerous?

  12. Mykkros says:

    To answer the question that jps591 asked, “will there be point bacteria when will not be able to “outevolve” the vaccines we use to fight them?”, I would answer yes. This is because we have already made tremendous strides in combating various diseases. For example, several decades ago smallpox used to be a devastating disease to people only a hundred years ago. However, due to modern medicine, the disease has been successfully completely eradicated from the world, thus showing that it is in fact possible that humans can produce medicine capable of destroying diseases for good. It is estimated that polio may be eradicated this decade and diseases such as yaws and malaria have goals to be eradicated in the coming years. Thus, while it may be difficult to fight such diseases, the problem is often not the medical needs to fight diseases but rather the political and social problems associated with combating and preventing disease.

    However, I agree with foldervral when he says that the “lack of physical stimuli could end up in a devolution of humanities physical capabilities”. If the immune system does not have to ever fight any disease, as could happen if people use too much antibiotics, we ironically leave ourselves more susceptible to contracting disease. However, I still believe that unless there is some colossal change to diseases such as influenza and the cold, I think that it is only a matter of time before the flu will be looked as a relic of the past like smallpox.

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