About the SA Blog Network



Opinion, arguments & analyses from the editors of Scientific American
Observations HomeAboutContact

Evolution details revealed through 21-year E. coli experiment

The views expressed are those of the author and are not necessarily those of Scientific American.

Email   PrintPrint

evolution bacteria e. coliIn 1988 an associate professor started growing cultures of Escherichia coli. Twenty-one years and 40,000 generations of bacteria later, Richard Lenski, who is now a professor of microbial ecology at Michigan State University, reveals new details about the differences between adaptive and random genetic changes during evolution.

Sequencing genomes of various generations of the bacteria, which had been frozen periodically over the years, Lenski and his team found that adaptive and random genomic changes don’t necessarily follow the same patterns. Rather than a plodding equilibrium, even in a consistent environment, the interplay between these two kinds of genomic changes "is complex and can be counterintuitive," Lenski said in a prepared statement.

Early changes in the bacteria appeared to be largely adaptive, helping them be more successful in their environment. "The genome was evolving along at a surprisingly constant rate, even as the adaptation of the bacteria slowed down," he noted. "But then suddenly the mutation rate jumped way up, and a new dynamic relationship was established."

By generation 20,000, for example, the group found that some 45 genetic mutations had occurred, but 6,000 generations later a genetic mutation in the metabolism arose and sparked a rapid increase in the number of mutations so that by generation 40,000, some 653 mutations had occurred. Unlike the earlier changes, many of these later mutations appeared to be more random and neutral.

The long-awaited findings show that calculating rates and types of evolutionary change may be even more difficult to do without a rich data set. "The fluid and complex coupling observed between the rates of genomic evolution and adaptation even in this simplistic system cautions against categorical interpretations about rates of genomic evolution in nature without specific knowledge of molecular and population-genetic processes," the paper authors wrote.

Such detailed pictures of mutation rates have been made possible since the advent of rapid genome sequencing. "It’s extra nice now to be able to show precisely how selection has changed the genomes of these bacteria, step by step over tens of thousands of generations," Lenski said.

The new data "beautifully emphasize the succession of mutational events that allowed these organisms to climb toward higher and higher efficiency in their environment," Dominique Schneider of the Université Joseph Fourier in Grenoble, France, and a coauthor on the paper, said in a prepared statement. The paper, published online today in Nature, also happens to come 150 years after Charles Darwin published his Origin of Species. (Scientific American is a part of the Nature Publishing Group.)

The findings might eventually help scientists better understand mutations in human diseases and infections. "Cancer progression is a fundamentally similar evolutionary process," Jeffery Barrick, a postdoctoral researcher at the lab and lead author of the paper, said in a prepared statement. And although the research team will continue to study the progress of the minute bacteria in search for more answers, he added: "We know an astounding amount about the details of evolution in these little Erlenmeyer flasks."

Image of E. coli cultures courtesy of Greg Kohuth/Michigan State University

Rights & Permissions

Comments 45 Comments

Add Comment
  1. 1. candide 2:17 pm 10/18/2009

    Evolution? Can’t they see that god is just messing with them? ;)

    Link to this
  2. 2. tharriss 2:25 pm 10/18/2009

    Interesting that by starting these experiments any time they want they can get god to come out of retirement and begin "designing" things…. on call at the whim of the experimenter.

    Hey god, time for you to get to work on another batch of species changes… punch your time card and get to work!

    Link to this
  3. 3. hotblack 4:20 pm 10/18/2009


    Link to this
  4. 4. tercero12 7:05 pm 10/18/2009

    Notice how it doesn’t say anything even suggesting macro-evolution. Micro-evolution (natural selection), as the article describes, has already been observed in nature.

    Nothing new here people, move along.

    Link to this
  5. 5. Johnay 9:43 pm 10/18/2009

    So-called "macro-evolution" is just lots of accumulated "micro-evolution".

    A journey of a thousand miles begins with a single step.

    Link to this
  6. 6. Gojira1974 9:54 pm 10/18/2009

    I doesn’t say anything about macro evolution because that wasn’t what it was studying. Did you just post that feel better about having a belief in fairy tales. I remember when "creation science" didn’t even accept micro evolution. DO RESEARCH AND PUBLISH OR SHUT UP!!

    Link to this
  7. 7. gylesw 8:35 am 10/19/2009

    It is hopeless… if someone accepts a version of events that has no facts to back it, then no amount of facts will make them change their mind.

    Thus the frustration of debate with people with a Creationist of ID viewpoint; they demand facts when they have none to support their own hypotheses and will argue around the vast factual support behind the theory of evolution, rather than actual present any viable alternative or falsification of it.

    I’ve already read elsewhere someone jokingly say they expect the evidence of 653 mutations to be countered with the allegation this reveals 1,306 missing links, and that’s not far removed from the response this will get from those who, no matter how hard one tries to lead them to rteason, still will not think.

    For a start, why can’t god do things the way he wants (evolution through natural selection etc..)? Why does it HAVE to be in a way that matches the accounts supposedly written by bronze age goatherds, when all the evidence is contrary to that?

    It’s almost as though the die-hard Creationists and ID’ers lack the faith to believe the evidence of their own eyes… or perhaps prefer beliefs that are comfortingly prescriptive in their nature.

    Link to this
  8. 8. silvrhairdevil 10:29 am 10/19/2009

    Wait wait wait! I got it! I got it!

    God Made Evolution.

    Problem solved. Case closed.

    Link to this
  9. 9. Dahlia 11:53 am 10/19/2009

    I don’t think the issue at hand is an evolution vs. divine creation debate. That’s the problem with these studies is the people who read them get too hung up on which side of that argument is right. Just look at the information from your side of the argument and make it mean something to you. This research has nothing to do with proving creationists wrong and everything to do with looking at mutation rates, and reasons for these mutations and how they population was affected by them. Start there. And leave God out of it.

    Link to this
  10. 10. frgough 12:47 pm 10/19/2009

    What facts? These guys spent 21 years and 40,000 generations just watching bacteria and tracking mutations. What a meaningless experiment. That’s like a physicist watching leaves falling from a tree and trying to derive the mathematics of gravitation.

    This is a wasted experiment. They should have used those 40,000 generations to PRODUCE an evolutionary pathway. EVOLVE eukaryotic bacteria from Prokaryotic bacteria using nothing but random mutation and selection pressure. If humans can descend from from a common primate ancestor in 17,000 generations, it should be trivial to re-evolve eukaryotic bacteria in 3 times that number of generations.

    Link to this
  11. 11. andsilverainfell 1:57 pm 10/19/2009

    frgough, it is impossible to evolve eukaryotic bacteria from prokaryotic bacteria. Eukaryotes are the result of endosymbiosis, not genetic change within a single prokaryote’s DNA. That’s something from middle school biology. (and if you don’t know endosymbiosis, it’s that one cell engulfed another cell and they struck a mutualistic relationship. thank Bacteria for your mitochondria)

    Do you have any concept of geologic time scales?
    Also, using the term "re-evolve" shows a complete lack of understanding of the force of evolution.

    Link to this
  12. 12. Telrunya 4:41 pm 10/19/2009

    The bacteria are still bacteria which is the point of the anti evolutionary crowd. For all the factual support the gylesw referances and the so called missing links envisioned, there is still not one single tracable evolutionary path from one species to another. Faith? Yes, evolutionists are chock full of it. To disprove a theory you dont necessarily have to come up with an alternative, though it helps. Adaptation has been proven. Evolution has not.

    Link to this
  13. 13. sjd0218 4:52 pm 10/19/2009

    Don’t wrestle with pigs. The pigs have fun and you get dirty.

    They search the internet for all articles on evolution and then bash them as though their personal faith is going to obliterated because all the world does not agree with their world view. You cannot change their minds and it is pointless to try.

    The most difficult subjects can be explained to the most slow-witted man if he has not formed any idea of them already; but the simplest thing cannot be made clear to the most intelligent man if he is firmly persuaded that he knows already, without a shadow of doubt, what is laid before him. – Leo Tolstoy.

    Link to this
  14. 14. JimV 7:49 pm 10/19/2009

    "If humans can descend from from a common primate ancestor in 17,000 generations, it should be trivial to re-evolve eukaryotic bacteria in 3 times that number of generations.

    At 17 years per generation, that would be 289,000 years, which is off by at least a factor of 24 (earliest primate fossils are over 7 million years old). "It should be trivial" needs some foundation as well. How do you know the conditions which produced eukaryotic microbes are present in the lab?

    Link to this
  15. 15. profpaul 8:37 pm 10/19/2009

    "To disprove a theory you dont necessarily have to come up with an alternative, though it helps. Adaptation has been proven. Evolution has not. "

    The same could be said about gravity, we can’t touch, feel, or prove it’s existence beyond the effects it manifests. Is Gravity real? Only if you accept the evidence. Otherwise it could passed over as a misconstrued myth as well. Most of science spends it’s time using causal effects and indirect evidence to prove theory (especially physics which most people have no problem accepting) .

    Link to this
  16. 16. royniles 10:42 pm 10/19/2009

    What this seems to show is that because of a lack of consistency between the two types of the adaptive functions over time, that mutations were directed more by the organism taking advantage of randomness for a purpose rather than reacting to random mutations and adapting those undirected changes to the existing environment.

    Link to this
  17. 17. jpill69 3:29 am 10/20/2009

    I might as well put in my 2 bits before the IDiots spoil it: this is a well-run experiment that gives precise evidence on how bacteria reproduce. That mutation rates vary over time, and how they varies, are important findings.

    Link to this
  18. 18. joeblog 4:39 am 10/20/2009

    Sorry, help me out here.

    Aren’t they saying that what’s driving mutation in the population is in large part independent of adaptation?

    I must have got that wrong.

    Link to this
  19. 19. gylesw 5:19 am 10/20/2009


    Errrr… I’m not saying ‘god made evolution’, so, nice straw man.

    I AM saying what a waste of time the anti-evolutionary buffonary of IDers and Creationists is, as it actually has nothing to do with any debate about god but invariably is misrepresented as such.

    Obviously one can take a very strong suggestion from evolutionary theory regarding the existance of some sort of divine being, but that’s all.

    Link to this
  20. 20. gylesw 5:35 am 10/20/2009

    The comments by frgough and Telrunya are good examples of the lack of knowledge typically displayed by nay-sayers in these kinds of discussions.

    Please note this is not an insult, just a description based upon what you have written.

    @ frgough; As already pointed out, expecting deriviation of eukaryotic bacteria from prokaryotic bacteria as a proof of evolution indicates your ignorance of what evolution actually is. Similarly your estimation of the number of generations shows a profound lack of knowledge about the subject. Would you respect someone who made sweeping claims about a scientific theory if everything they said showed they didn’t know the first thing about it? How do you expect people to react to you in similar circumstances?

    @ Telrunya; you say "there is still not one single tracable evolutionary path from one species to another". So, the cladistic and genetic studies that show very clear paths from one species to another are what? Fabricated? Unknown to you? Not understood by you? Which is it?

    Link to this
  21. 21. SimonUK 6:29 am 10/20/2009

    That isn’t how evolution works! Hence NATURAL SELECTION! You cannot start at point A and determine point B! It is rather more complex and chaotic that that.

    Link to this
  22. 22. jpill69 11:21 am 10/20/2009

    gylesw, one of the more bizarre twists of this debate is there are people on both sides of the fence who INSIST evolutionary theory says God does not exist, and by that stretch are actually arguing for the opposite side.

    Link to this
  23. 23. jpill69 11:37 am 10/20/2009

    gylesw, you point out just another example of creationists’ instatiable denial of the facts, yet they continue to yammer as if scientists have nothing better to do than answer over and over their trumped-up objections.

    Link to this
  24. 24. joeblog 3:01 pm 10/20/2009

    So this finch’s beak is the shape it is because it allows it to succeed in this niche in the ecosystem
    it’s the shape it is because that’s just one random possibility out of many.

    So ‘Survival of the fittest’ doesn’t explain everything.

    In fact for some things there may be no ‘explanation’ per se. The observed effects may be just random.

    And if there’s no explanation there’s no basis for a counter argument against someone else’s preferred explanation …

    Link to this
  25. 25. dskan 7:19 pm 10/20/2009

    Wow. The timespan to evolve the Eukaryotes from Prokaryota is as long or longer than the entire span of Eukaryota since then. Prokaryotes reigned for 1.4-1.9 billion years before the Eukaryotes, while Eukaryotes have been around for 1.6-2.1 billion years. Just so you understand, Homo arose 2.1 million years ago. That means the triviality of human evolution occurred in 0.1% of the time of the Eukaryote innovation. By your illogic then, a better experiment would be to watch these evolve for 13 million generations and hope something happens, roughly 326 years. Let me know how that works out for you.

    Link to this
  26. 26. hotblack 7:34 pm 10/20/2009

    It’s not random. You know what, if you enjoy this, you might also enjoy arguing particle physics with those quacks over at CERN. What? You don’t know anything about particle physics? Don’t let that stop you from opening your mouth and expressing your opinions first. Heaven forbid you should actually read a book on the basic fundamentals of the concepts before engaging in a discussion about a topic. Who educated you people? Oh, that’s right….

    Link to this
  27. 27. hotblack 7:37 pm 10/20/2009

    You got a 1,700 year old education.

    …and it shows. Your knowledge is stuck in the third century AD.

    Link to this
  28. 28. gylesw 5:13 am 10/21/2009


    Ah, but some people LIKE wrestling with pigs ;-)

    Not here, but elsewhere on a discussion board for people recovering from involvement with Jehovah’s Witnesses, I have been round the block numerous times with this.

    My experience is that the actual debators against evolution are generally intractable. As mentioned, they don;t know what they are arguing against, so proving something to them is a tad hard as they don’t have a clear enough idea of what it even is to even recognise it being proved.

    But I know from many, many comments from lurkers (non-poosters) that it is debate like this which actually move the silent majority (as most ex-JW’s are Creationists at least initially) from "evo is definately wrong" to a more reasonable and moderate position where they actually recognise the massive lack of knowledge and literalism enherant in the Creationist stance and the vast evidential weight behind evolutionart theory.

    Link to this
  29. 29. gylesw 5:19 am 10/21/2009


    Yet another person whose comments show they don’t know enough about the topic to have an informed opinion. Way to go at proving my point.

    Random variations that give a small advantage (in terms of untimate reprodcutive success) are more likely to be passed on to the next generation than those with a neutral of negative effect on reporductive success.

    Isn’t it a little arrogant to doubt a theory you’ve not bothered to learn properly?

    Link to this
  30. 30. joeblog 8:50 am 10/21/2009

    @’hotblack’; as the authors, "random genomic changes", and gylesw ,"Random variations", point out, it is about randomness.

    ‘gylesw’; When you use reproductive success as a guiding principle you just mean anything not ruled out by biology; the environment stays the same yet what’s reproductively successsful keeps changing. The advantage is no longer described by Darwin’s selection principle. Is there a new principle? Doesn’t it leave people free to throw in their own favourite principle?

    My problem with evolution as a scientific theory is that, apart from having just one run of the experiment, if a result like this came up in particle physics, to take that example, it would be greeted with delight – a chance to question the fundamentals of the theory. Here it’s seen as a threat.

    (‘hotblack’ and ‘gylesw’; As two people of your intellectual superiority know, simply pointing out the fact is not an argument itself.
    I thought it was intelligent designers who believed in arguments from authority.)

    Link to this
  31. 31. mo98 10:50 am 10/21/2009

    Open Watcom C has some credible sample source code for simulating bacterial "life" that can be parametrized with seemingly non-adaptive birth and death rules for over 30 thousand generations. Reading elsewhere about how the leader portions of chromosomes cannot replicate yet function to guard against random mutation narrows things down to some more potentially exciting research. Multidimensional graphical processing unit languages can accelerate the simulation of bulk cell division. Herd influence and containment morphing may ultimately determine when a reproductive pattern should shift between probability and tendency in those, perhaps, prime number division cases when new ideas for randomness are welcome after an adaptive revolution has finished its "struggle".

    Link to this
  32. 32. joeblog 12:12 pm 10/21/2009

    mo98; I think I understand you to say that (some of the) long term development of population characteristics can be effectively modelled by rules that ignore adaptation as a guiding principle.
    You say the principles that are invoked to explain what’s seen are things like "Herd influence and containment morphing" which sound more like emergent properties than anything predictive.

    Most people who work in evolution will, when pressed, accept that adaptation may not explain all the variety of the natural world. Or at least we can’t be sure it does. They don’t seem to realise the consequences of this admission. Where do we draw the line? How much of the world is down to adaptation moderating random change? How much is due to unmoderated random change wrongly explained away by some evolutionary biologist’s ‘Just So’ story?

    Link to this
  33. 33. silvrhairdevil 12:57 pm 10/21/2009

    "The following is a direct response to this comment.

    Errrr… I’m not saying ‘god made evolution’, so, nice straw man."

    Just because my post followed yours does not mean it was addressed to you.
    It’s not all about you, buddy.

    *I* said God Made Evolution because I am tired of the endless rehashing every time the word Evolution gets printed.

    If god makes things evolve, everyone can be happy. Okay?

    Link to this
  34. 34. alandaglish 1:49 pm 10/21/2009

    This is getting a bit stupid, the discussion is simply veering towards, as always when the word evolution occurs in a paper, "The bible, fact or fiction" .
    If the ID brigade need it why cant they believe that their ID’er designed the evolutionary process? The explanation of it was left to us mortals as a form of learning process along with physics, cosmology etc, to take us further along the path it had prepared for us. Both sides (and neutrals) must surely appreciate that this approach leaves us all in the clear.

    Link to this
  35. 35. Telrunya 4:40 pm 10/21/2009

    Lack of knowedge? Thank you for such an in depth review of my educational history or my credentials to make a comment on this particular subject. I would sink to your level by addressing you as a moron for making such leaps but lets try adressing your question as if it were not rhetorical and an actual search for understanding.

    Fabricated would be closest to the mark. Take for example Lucy. No feet. The hips are shattered and put together to resemble upright walking but what gives it away is the hands. The elongenated digits that are more indicitive of ape like walking than upright as well as the shape of the upper thigh bones. Many of the so called links are widely open to such interpitation. Evolutionists want them to fit into the mold and rather than take all such evidence into account and allow the fossiles to speak for themselves they brand them. Which leads to catastrophes like piltdown man. No I dont believe they are malicous fabrications in as much they know better and deny it to make the fossiles seem to be what they aren’t. I do believe their faith in evolution is so strong it blinds them to the clues that the fossiles they are looking at dont fit in perfectly into the evolutionary chain as they want and therefore are scientificly suspect from the begining. Wait mroe more such revelations to come from the so called hobbit people once actually objective scientist can get access to the fossils.

    As for the genetic studies you referance they too are widely open to interpretation and only the interpretation that corresponds to evolution makes the headlines and many times, if not universally, is not the interpretation that actually fits best with the given sample.

    Link to this
  36. 36. jpill69 1:09 pm 10/22/2009

    alandaglish wrote:
    If the ID brigade need it why cant they believe that their ID’er designed the evolutionary process?

    My reply:
    If only…

    Link to this
  37. 37. ray stasionis 1:16 pm 10/22/2009

    To Candide: This "God" of yours that you speak so highly of… is an idiot!

    Link to this
  38. 38. g_in_dallas 6:05 pm 10/22/2009

    agree completely with frgough – only the fact sir

    Link to this
  39. 39. DeeCee08 9:23 am 10/27/2009

    I think you’d be significantly more productive if you’d explain what clues are to be searched for in fossils that would support creationism and/or intelligent design. It seems you fall substantially short of supporting that untenable position as you instead opted to hurl insults and barbs.

    Link to this
  40. 40. DeeCee08 9:31 am 10/27/2009

    What you mean to suggest that bronze age goat farmers are not smarter than people able to launch themselves into space? That is an outrage! ;) ~

    Link to this
  41. 41. VMartin1 10:18 am 10/27/2009

    Evolution has probably nothing to do with "random mutation" and "natural selection".

    Link to this
  42. 42. VMartin1 11:06 am 10/27/2009


    Link to this
  43. 43. robert schmidt 5:19 pm 01/23/2010

    @frgough, once again you honour us with your ignorance and hatred of science. Here is an idea, why don’t you actually do some science and prove the seemingly endless stream of B.S. that you deposit here? You seem to believe you are doing us all a favour by revealing obvious flaws in well established science, what you are really doing is showing us all how little you know about the things you criticize. The holes in the theories are ultimately holes in you knowledge. The only thing that is meaningless here are your comments.

    Link to this
  44. 44. robert schmidt 6:09 pm 01/23/2010

    @Telrunya, "As for the genetic studies you referance they too are widely open to interpretation and only the interpretation that corresponds to evolution makes the headlines and many times, if not universally, is not the interpretation that actually fits best with the given sample." please prove this! Or is this yet another one of the lies you make up in some incomprehensible effort to make it sound like you have actual scientific backing. Please demonstrate how you know that the results of genetic studies have been fabricate to support evolution. You are accusing science of fraud, what is your evidence?

    I have asked you many times already but here we go again. Prove your God hypothesis! Instead of showing us how little you know about evolution and science in general please prove your proposition that god exists. Until you can, your I.D. argument does not even meet the basic criteria of a hypothesis. You place an exceptional burden of proof on evolutionists so; unless you are a complete hypocrite, do us the favour of proving your assertions. If you can’t then you really need to understand that what you say is meaningless.

    You just don’t seem to get it. The reason evolution does not make sense to you is because; A) you don’t want it to because you are inextricably tied to your world view, it is part of your identity, without which you wouldn’t exist and; b) you don’t understand evolution! You must be aware of the fact that you haven’t studied the subject. You must be aware that everything that you do know was implanted in your head by religious fanatics. Reading what you write is like listening to my four year old nephew explain how rocket-ships work, except instead of being cute, you are annoying. Telling you that you are ignorant is not an insult, it is the truth. It is clear to most everyone here. I can’t imagine why you would think otherwise.

    Link to this
  45. 45. alandaglish 6:20 am 01/24/2010

    @Telrunya, "As for the genetic studies you referance they too are widely open to interpretation …………"
    How come someone can make a statement like this yet stoutly deny that the Bible is not?

    The process we call evolution is open to many interpretations It is in the nature of things that it is difficult to get any two scientists to agree on any set of details but how about postulating that making something difficult to understand is the creator’s way of forcing our minds to evolve. Following Darwin perhaps only the fittest interpretation of the observable facts will survive. In this case is the evolutionary process part of the creator’s grand design?

    Link to this

Add a Comment
You must sign in or register as a member to submit a comment.

More from Scientific American


Get All-Access Digital + Print >


Email this Article