We Are Myriad

Do I contradict myself?
Very well then I contradict myself,
(I am large, I contain multitudes.)

—Walt Whitman, “Song of Myself”

Creationists who think themselves clever sometimes ask why, if evolution is true, we don’t see bacteria re-evolving into multicellular organisms. But, as is often true of creationists, this taunt gets the situation completely backwards. Evolution is not a teleological march of progress but a blind algorithm, concerned exclusively with reproductive success. Looked at in this light, a far better question is why multicellular life ever evolved at all. In the metrics of success that evolution is concerned with, bacteria are our undisputed superiors. They far outnumber us; they thrive in environments we could never survive in; and, if they were ever to disappear, all of the so-called higher life on this planet would swiftly follow them into extinction.

Above: Bifidobacterium, one of the first species to colonize a newborn’s intestinal tract (usually introduced through the mother’s breast milk). Image credit: MicrobeWiki.

To drive this point home, consider this mind-boggling statistic: in the body of every healthy human being, there are ten times as many bacterial cells as there are human cells. If this seems impossible, realize that bacteria are prokaryotes, lacking the complex internal structure of, and therefore much smaller than, our own eukaryotic cells. Most of the bacteria in the human body live in the intestines, and the 15 trillion or so bacteria in a healthy gut would just about fill a ten-ounce soup can.

Our gut flora are not invaders or pathogens, but an important part of the body’s normal functioning. Far from being mere passengers, they live in an intimate symbiosis with the cells of the digestive tract. They play a vital role in extracting nutrients from food: mice raised in absolutely sterile environments need to eat 30% more to stay at the same weight as normal mice. (This partnership is more prominent in herbivores like cows or termites, whose resident bacteria enable them to digest the woody plant tissues that no animal could otherwise eat – but our natural bacteria do the same for us, helping break down complex carbohydrates and proteins that the body cannot digest on its own.) In fact, it’s believed that the gut flora are a vital barrier against disease: by occupying all the niches within the body, they leave less room for genuinely pathogenic species to get a toehold.

Jessica Snyder Sachs, in her book Good Germs, Bad Germs, quotes an unforgettable portrait of the microbial jungle that lives just in the human mouth alone:

…I was able in my mind’s eye to zero in on the little fleshy crevices around Tom’s and Jenny’s teeth as they ate their meal and to see the turmoil of microbic life there, the spirochetes and vibratos in furious movement, the thicker corkscrew-like spirilla and vibrios gliding back and forth and the more sluggish or quiet chains and clusters and colonies of bacilli and cocci, massed around or boiling between detached epithelial scales and the fibers and debris of cells and food particles. Like the great and beautiful animals in whose mouths they live, these too are organisms, living things; and I could imagine them, quite like Tom and Jenny, making the most of the sudden accession of nourishment after a long fast. (p.36)

Above: Staphylococcus epidermidis, a common skin bacterium. The average human being has three to sixteen of these living on the surface of every skin cell. Image credit: NIAID.

But our relationship with bacteria is more intimate still. Other species of them do not just live within our bodies, but within our cells, and it is only because of them that life like ours is possible. Richard Dawkins puts it succinctly in The Ancestor’s Tale:

All our cells are… stuffed with bacteria which have become so transformed by generations of co-operation with the host cell that their bacterial origins are almost lost to sight… [They] have become so intimately enmeshed in the life of the eukaryotic cell that it was a major scientific triumph to detect that they were there at all. (p.537)

Each of our cells contains organelles called mitochondria. Colorfully speaking, they are the cell’s power factories – the reason we breathe oxygen is so the mitochondria can use it in the production of ATP, an energy-carrying organic molecule that’s used as a common currency for many of the cell’s chemical reactions. Mitochondria also have their own DNA – not the complexly packaged chromosomes of our own nuclei, but simple circular chromosomes similar to those of bacteria – and are capable of self-replication, dividing autonomously within the cell.

Above: The famous Escherichia coli, one of the most common gut bacteria. Most strains are harmless. Image credit: NIAID.

The evolutionary biologist Lynn Margulis is famed for discovering the origin of mitochondria: as their separate DNA hints, they were once free-living bacteria. Long ago in the mists of evolutionary history, these bacteria merged with the cells that would ultimately become our ancestors. Both cells benefited from this symbiotic partnership, and so it persisted and thrived. Over long stretches of time, the mitochondria lost most of their DNA, as it was no longer needed in their new environment. Though they have become so intertwined with us that they are no longer capable of independent existence, they remain as traces of the ancient eukaryotic union that was the first flowering of life recognizably like ours. Incredibly, even today, we can guess at the identities of those species involved in this historic partnership. From Richard Dawkins again:

…molecular comparison tells us the particular group of bacteria from which mitochondria are drawn. Mitochondria sprang from the so-called alpha-proteo bacteria and they are therefore related to the rickettsias that cause typhus and other nasty diseases. (p.539)

Though their wild relatives cause us grief, the tame mitochondria are essential to life as we know it. And not just our life, either: chloroplasts, the organelles that give green plants their color and make photosynthesis possible, are, like mitochondria, the remnants of an ancient symbiosis. For both plants and animals, the seen depends on the unseen: each of us is not a single organism but a myriad, a kind of ecosystem made up of hundreds of different species. If it were not for our microbial partners, our kind of life could not exist. This insight, and the humility it brings, are worth remembering whenever we Homo sapiens are tempted to imagine ourselves the crowning glory of life on Earth.

About Adam Lee

Adam Lee is an atheist writer and speaker living in New York City. His new novel, Broken Ring, is available in paperback and e-book. Read his full bio, or follow him on Twitter.

  • http://www.johnnysstew.com/cool/coolwet J

    Right on. Dawkins’ best book–in my opinion–is “The Ancestor’s Tale” in which he dissects (not to say “skewers”) the term ‘primitive organisms’ or ‘primitive life forms’. He says that there are NO primitive life forms alive today: Each and every species alive today is 100% efficient, successful, and ‘advanced’. Biological ‘success’ means you get enough to eat, you resist or escape from predation and you reproduce. Dogs, primates, dolphins, humans: A large brain and a mammalian metabolism is just one possible answer to these challenges. There is nothing intrinsically good, special, or ‘advanced’ about it. The bacteria in our intestines have every bit as good a ‘solution’ to the problems of living as we do.

  • http://www.johnnysstew.com/cool/coolwet J

    Oh and just to add on something else: NOTHING in this definition of ‘fitness’ (eating, avoiding being eaten, reproducing) should/can be read to classify certain groups of people as ‘unfit’ to live, nothing in it justifies any form of genocide, nothing it in justifies antisocial, brutal or criminal behavior and nothing in it can be read as a condemnation of human cultural activities (i.e. studying dead languages, listening to music, or, *sigh*, yeah I guess, religious observance).

    ‘Survival of the fittest’ DOES NOT MEAN that we just push people in wheelchairs off the edge of cliffs, brush off our hands and high-five each other on a Darwinian job well done. No. If we create social programs or systems of morality or whatever so that people with disabilities are able to live longer, get the resources they need to survive, and are able to form families and reproduce (or even *not* reproduce, but just live and contribute in any way at all to the human species), well then we’ve increased their fitness haven’t we?

    Have a little faith in your own social teachings, Christians: The meek really DO seem to inherit the earth, insofar as societies–yes, even religious societies–that live by the sword tend to die by it quite swiftly. The Thousand-Year Reich lasted, what, 14 years or so? The USSR and imperial Japan hung on for maybe 80 years or so each but both then completely imploded. So too with the very Christian ‘Crusader States’ of the Levant. The variously pagan or Muslim Mongol, Turk and Mamluk empires were did well only until they ran out of people to kill or flat terrain to ride across.

    And the ‘Permanent Republican Majority’? Well, we’re seeing the fate of that right now, aren’t we?

  • http://www.dvorkin.com David Dvorkin

    This is a great sentence: “Evolution is not a teleological march of progress but a blind algorithm, concerned exclusively with reproductive success.”

    It highlights the misunderstanding common not only among creationists but among the general public.

  • http://friendlyhumanist.blogspot.com Timothy Mills

    Beautiful post. Thankyou.

    It reminds me of Greg Bear’s excellent (and disturbing) story, “Blood Music”. When I first read it, the scene Bear closed with seemed alien, frightening, and ambiguous between apocalypse and hopeful transcendence. In light of the above, though, it could almost be called prosaic. (But in a fun way.)

  • velkyn

    No “we are legion”? ;)

    Great article. I’m favoriting this so I can direct the usual willfully ignorant creationists to it.

  • Adam

    Nice post, good info.
    I know that in the post the Catholic Church was not mentioned, but are often seen as creationists, which is false, and just wanted to reiterated that it is not against evolution…if anyone was confused about that.

    Evolution is not a teleological march of progress but a blind algorithm, concerned exclusively with reproductive success.

    The order in the world would say otherwise…

    This insight, and the humility it brings, are worth remembering whenever we Homo sapiens are tempted to imagine ourselves the crowning glory of life on Earth.

    Our Intellect and will, which gives us our ability to act, to do things or not to do them, based on knowing what is right and wrong, gives us a freedom no other being on earth has…which is why we are the crowning glory of life on earth.

    Anything less is just comparing man to something inferior, like bacteria

  • http://anexerciseinfutility.blogspot.com Tommykey

    Good post Ebon.

    The relationship between bacteria and human life makes me think of the scene in Casino where little Joe Pesci is chewing out Robert De Niro in the desert(expletives deleted).

    “Let’s get one thing straight you $@^#$&#%&$%&$! You only exist out here because of me! With out me, you, personally… every @##@$% will take a piece of your ass!”

  • Curtis

    If you are interested in learning more about mitochondria (or evolution), I highly recommend Power, Sex, Suicide: Mitochondria and the Meaning of Life by Nick Lane. It was nominated for the Aventis prize for best science of the year. It goes into details of energy productions in cells, Margulis on symbosis, mitochrondial genes, etc and still remains enjoyable to someone like me without a biology background.

    http://www.amazon.com/Power-Sex-Suicide-Mitochondria-Meaning/dp/0199205647

  • NoAstronomer

    As I always tell my kids : bacteria own the planet, we just live here.

  • Mr.Pendent

    ‘Survival of the fittest’ DOES NOT MEAN that we just push people in wheelchairs off the edge of cliffs, brush off our hands and high-five each other on a Darwinian job well done.

    Oops. Sorry about that.

    If we create social programs or systems of morality or whatever so that people with disabilities are able to live longer, get the resources they need to survive, and are able to form families and reproduce (or even *not* reproduce, but just live and contribute in any way at all to the human species), well then we’ve increased their fitness haven’t we?

    Actually, unless they reproduce, we haven’t changed their Darwinian fitness at all, have we? Isn’t reproduction the ultimate arbiter of evolutionary success? Not surviving the current environmental conditions, but surviving and producing offspring?

    Mind you, I’m all for helping folks when they need it, and not having children, for that matter. But when you look at the rates of reproduction in the modern world, gives you a whole new way to evaluate things like education, economic success and the like. Evolutionarily speaking, Bill Gates is considerably less successful than “Jon and Kate” (as illustrated in Idiocracy).

    Frightening, isn’t it?

  • Maynard

    Mr. Pendant, reproduction isn’t always the DarWINian/evolutionary goal. In The Selfish Gene, Dawkins shows how supporting siblings can be as, or more, beneficial as producing and supporting your own offspring.

    Idiocracy: I hope someday we’re able to look back on this movie the same as we can now look back on Orwell’s 1984. *fingers crossed* (Of course 1984 may just have gotten the year wrong.)

  • http://www.patheos.com/blogs/daylightatheism Ebonmuse

    I’ve updated the post with some pretty pictures.

  • Alex Weaver
    Evolution is not a teleological march of progress but a blind algorithm, concerned exclusively with reproductive success.

    The order in the world would say otherwise…

    Unless you are contending that what you characterize as “order” (which is what, exactly?) is neutral or detrimental with respect to reproductive success, there is no reason other than failure of imagination to contend that the existence of “order” disproves the contention you purport to dispute.

    This insight, and the humility it brings, are worth remembering whenever we Homo sapiens are tempted to imagine ourselves the crowning glory of life on Earth.

    Our Intellect and will, which gives us our ability to act, to do things or not to do them, based on knowing what is right and wrong, gives us a freedom no other being on earth has…which is why we are the crowning glory of life on earth.

    We have certainly developed these faculties to a remarkable extent, and have a capability in this regard which vastly exceeds that of other social animals, which generally display similar behaviors at a less developed and complex intellectual level. I’m a little vague on the transition from “highest achiever in one area” to “crowning glory of life on earth” though.

    Anything less is just comparing man to something inferior, like bacteria

    Do you actually not recognize this as a circular argument?

  • Christopher

    Adam,

    The order in the world would say otherwise…

    What order? All I see in nature is chaos – animals killing to live, earthquakes and high-velocity storms demolishing all forms of life, stars exploding in supernovas, meteors crashing into planets and much more! If there is anything in nature that could be contrued as “order” I don’t see it…

  • http://www.johnnysstew.com/cool/coolwet J

    Pre-emptive apologies for the long post to come:

    Actually, unless they reproduce, we haven’t changed their Darwinian fitness at all, have we? Isn’t reproduction the ultimate arbiter of evolutionary success? Not surviving the current environmental conditions, but surviving and producing offspring?

    Mind you, I’m all for helping folks when they need it, and not having children, for that matter. But when you look at the rates of reproduction in the modern world, gives you a whole new way to evaluate things like education, economic success and the like. Evolutionarily speaking, Bill Gates is considerably less successful than “Jon and Kate” (as illustrated in Idiocracy).

    Frightening, isn’t it

    Nope. Just reproducing numerically isn’t the pure definition of fitness. In nature, there is a blurry divide between r- and k-type reproduction strategies. R-type is your insects, your bacteria, your frogs: Pretty much everything except for birds, mammals and a few reptiles. They have lots of offspring and they have them quickly and then die quickly. There is a huge mortality rate, but the species goes on. They are “fit”. R-type reproduction is an advantage when confronting rapid environmental changes in a single environment.

    K-type organisms have long lifespans, and raise a few offspring relatively slowly, at great initial resource-cost. Bear cubs, penguin chicks, whale calfs and baby humans. The level of mortality is much lower (although the death of any one organism is a potentially huge loss) but the individual organism is generally instilled with a “culture” (if you will) that allow it to flexibly adapt to multiple situations. It’s notable that K-type organisms tend to be far-travelers (i.e. whales, that migrate the entire length of the western hemisphere each year) whereas R-typers tend to stay in one place.

    Both r-types and k-types are both perfectly ‘fit’; as I said before, there’s no ‘primitive’ species out there. They’ve just adopted different strategies. In broader terms, R-typers are set up to ‘adapt in place’ whereas K-types are set to ‘nomadize’ and find a new, better environment if/when the current one becomes crowded or uninhabitable.

    Now humans are ONE species, but it could be argued that there are K- and R-type humans as well (and it should be IMMEDIATELY caveated that they often live side by side, quite peacefully and prosperously). Some people have lots of kids, some have a few and expend lots of resources on them. You can fill in the obvious additional details about class, education, women’s empowerment, etc.

    Everything in me reacts *against* telling other people that they are ‘living wrong’ (except if they’re doing obvious harm to others). Criticizing the arch-Catholic family for having 8 kids and overpopulating the earth seems only fractionally less silly than criticizing the lesbian couple and their adopted Chinese or artificial-insemination-conceived kid for failing to give him/her a proper male parental figure, etc: In either case, the kids are probably Alright and I should just Butt Out.

    “Idiocracy” was a laugh, but only that: I don’t find it either particularly prescient (i.e. birth rates are actually dropping *worldwide*, including in a lot of places in Africa, Latin America and Asia that might surprise you) nor particularly frightening (i.e. education is ALSO going up worldwide; Kenya just got universal, free primary education set up a few years ago and Brazil just got compulsory secondary schooling established, along with an excellent system of giving poor families small allowances of food or money to allow them to keep their kids in school).

    As regards ‘fitness’ without reproduction, well here’s where we’ll have to be a little imaginative and expand on Darwin (though we can still make reference to examples from the animal world). “Fitness” really means the *species* survives, not the individual organism. If a person does not reproduce but contributes to the survival of others, then they’ve enhanced species fitness. A person with mental or physical disabilities might contribute to their family’s life–in totally unmeasurable ways–that nevertheless make life easier and less stressful. Lots of K- AND R-type animals do this: Remember, there’s only one fertile female in an entire honeybee colony, but without the other 10,000+ female workers, the whole species would collapse overnight.

    So no, fitness is NOT ‘just reproduction’.

  • Jim Baerg

    “Fitness” really means the *species* survives, not the individual organism. If a person does not reproduce but contributes to the survival of others, then they’ve enhanced species fitness.

    This part is a misunderstanding of evolutionary thinking. The closest ideas to that that have some acceptance among biologists are kin selection & group selection ideas.

    Kin selection is the idea that if you help eg: your nieces & nephews survive, you are indirectly passing on your genes. Group selection is the idea that genes for helpfulness within the tribe will help the tribe in competition with other tribes & so those genes will persist & spread. Kin selection is well established. It is controversial whether group selection ever has any significant effect.

    The notion of ‘the good of the species’ as a goal of evolution is wrong.

  • Entomologista

    “Fitness” really means the *species* survives, not the individual organism.

    You’re entirely wrong. There’s no such thing as group selection. The closest you get is kin selection, which leads to things like eusociality (the technical term for how bees and ants live). What bees do is NOT group selection. Why? Because the workers share 75% of their DNA with one another and with the queen. Besides, species don’t actually exist anywhere but inside our own heads. It’s useful to group like organisms, but it’s not like those organisms reproduce by our rules just because we’ve grouped them.

    It’s notable that K-type organisms tend to be far-travelers (i.e. whales, that migrate the entire length of the western hemisphere each year) whereas R-typers tend to stay in one place.

    I also disagree with this statement. Insects can travel large distances, especially when aided by wind and water. Sea turtles also exhibit little care for their offspring yet migrate huge distances.

    I seem to remember reading that termites actually produce a few of their own cellulases. But yes, they mainly rely on symbiotic bacteria.

  • http://www.johnnysstew.com/cool/coolwet J

    This part is a misunderstanding of evolutionary thinking. The closest ideas to that that have some acceptance among biologists are kin selection & group selection ideas.

    Strictly speaking, yes. But it’s still a valid way of looking at things if you view competition (and cooperation), reproduction and evolution as the effort that *genes* make to survive and spread rather than the effort than organisms make, a la “The Ancestor’s Tale”.

  • Leum

    Also, intelligence is linked to genes in humans, but not determined solely by them. Our ideas and cultures can travel and propagate through education, communication, and relationships. The idea that the unintelligent will outbreed the intelligent leading to a decline in intelligence (whew, need to cut back on word reuse) fails not just because of alternative reproduction strategies, but also because it is overly simplistic. Many of my best teachers had only one child, but they gave hundreds, even thousands, of their students many of the same abilities their children received.

  • D

    “Crowning glory,” my eye. It’s been said that our search for “intelligent” life elsewhere in the Universe is like elephants looking for “trunk-having” life elsewhere in the Universe: our brains are just one distinguishing feature, one particular type of adaptation among many. Being able to stop and think reduces reaction time (look at flies, for instance) and carries with it costs as well as benefits. In order to say that we’re “better” than anything – not better at something, mind you, but that our minds are better than some other species’ primary survival mechanism – you have to bring in a value system and say why that’s better. And then your statement is revealed for the arbitrary anthropocentrism that it is.

    There is no action humans have performed that has not already been eclipsed in Nature. Our finest art pales in comparison to the breathtaking vistas both on our planet and out in space. Both our life-giving goodness and raw destructive power are no match for even a single star. Our most vicious acts of genocide stand mute next to the mass extinctions shown in the fossil record. Our petty conflicts on this tiny rock are nothing to the colliding Antenna galaxies.

    Crowning glory? Hardly. We’ve had a mixed run, at best, and many of the worst marks on our record have been caused specifically by this anthropocentric hubris, whether it has been voiced through religion, politics, or any other mindset that says we’re somehow “better” than anything else around.

  • D

    Darn it, there needs to be an edit button. I meant either “increases reaction time” or “reduces reaction speed.” Point is, our reaction times suffer because of our big brains.

  • Tom

    The notion of ‘the good of the species’ as a goal of evolution is wrong.

    I’m not sure I agree. A particular mutation in an individual that inclines them to instinctively preserve other members of the species is perhaps less likely to propagate than one that improves their reproductive capacity directly, but that doesn’t guarantee it won’t. If it’s not immediately beneficial but not actually detrimental either, it could still spread through a population – and if it were to spread through one isolated population of a species but not through another, over time that population would see a benefit and perhaps displace the other.

    I wouldn’t refer to evolution as having “goals”, either, since it’s an emergent process – call them “likely effects” or something.

  • Brad

    This insight, and the humility it brings, are worth remembering whenever we Homo sapiens are tempted to imagine ourselves the crowning glory of life on Earth.

    Good thought. We can still count ourselves best amongst the planet with many measures, but there are many measures still that show otherwise. In general, most people are blind to this, preferring human-centric measures of our dominance and superiority. One thing I don’t get about this article, though, is the opening quote from “Song of Myself.” The original meaning had that Whitman, as a person, contained thoughts from many viewpoints even though he was one guy. In other words, he was a “dividual.” The substitute in meaning for this article seems arbitrary.

    The order in the world would say otherwise…

    What order? All I see in nature is chaos – animals killing to live, earthquakes and high-velocity storms demolishing all forms of life, stars exploding in supernovas, meteors crashing into planets and much more! If there is anything in nature that could be contrued as “order” I don’t see it…

    Pattern and chaos are inextricably linked. Even within chaos there must be pockets of “order.” The transient emergence of self-guided organization within disorder* is mathematically necessary under our conditions; and so here we are on planet Earth amidst the universe.

    *Or the present results of initial disorder during the first moments of the Big Bang.

  • http://thegreenbelt.blogspot.com The Ridger

    Creationists who think themselves clever sometimes ask why, if evolution is true, we don’t see bacteria re-evolving into multicellular organisms.

    Ummm … because there are already multicellular organisms filling that niche? Specialized ones? So no brand-new one could compete?

  • http://uncyclopedia.org/wiki/User:Modusoperandi Modusoperandi

    The Ridger: you see the same argument but with abiogenesis, as well. In that case, though, it’s that all of the precursors of life are now food for the life that’s already here.

  • Edgardo

    Creationists do not understand that evolution is not an absolute; it varies every generation and it is hard to pinpoint how a species or bacteria will evolve. First of all, bacteria became animal cells through the mitochondria and bacterial fission not from a chronology these fools are using. In fact, it is proved we are the ancestors of bacteria since bacteria contains some familiar characteristics of our cells. Also, human behavior is not attributed to some made up deity but to their environment, relationships, customs, and other patterns that cannot be explained by religion but only through neurology and the psychology.

  • Snoof

    I realise this is a total necropost, but I just wanted to attempt to correct a misapprehension.

    D: It’s not that scientists are looking for “intelligent” life because we think it’s more important than “unintelligent” life. I imagine most biologists would be overjoyed at the discovery of _any_ extraterrestrial life at all. Thing is, “intelligent” life may turn out to be easier to locate, because (assuming their intelligence is like ours) they could be doing things like transmitting information on the radio spectrum, building Von Neumann probes and sending them out, detonating antimatter bombs and looking for intelligent life; things which are easier to spot from our position than, say, alien microbes floating in the atmosphere of a gas giant. Not to suggest that the microbes wouldn’t be incredibly cool to take a look at, mind you.


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