We Are Nobody: Contingency and Convergence in Evolution

It is the year 2092. Nemo Nobody is the last mortal on our planet. At 117 years old, the brittle Nemo is almost at the end of his life. Everyone around him will live forever, whereas he will be the last one to die. Nemo spends his last days in a hospital where he features in a reality show and is interviewed by a journalist every day. But the journalist finds reconstructing Nemo’s past difficult, as many of his memories seem to contradict one another. For example, when his parents got separated, Nemo either had to stay with his father in England, or move to the United States with his mother. But Nemo never really made that choice. He remembers both living with his mother and taking care of his sick father. Later he remembers being married to three different wives, in varying degrees of happiness. It is as if Nemo never makes a decision. When he is confronted with a fork in the road, he walks both paths. Looking back at his life it as if he is peering through a kaleidoscope – seeing all the possible lives he could have lived at once.

The movie Mr. Nobody raises some mind-boggling questions about choice and consequence. How many different lives could you have lead? What if your parents had moved to a different town when you were young? What if you had studied medicine, instead of psychology? What if you had missed that bus and never met your current partner? Change just a few critical details of your personal history, and you would end up leading a different life altogether. You are where you are know, because a long chain of improbable events brought you there. This dependency on the past is called contingency. Sometimes the dependency is obvious. If you choose not to attend high school, you cannot attend college for example. Other dependencies, such as the launch of your company after bumping into your future business partner at the airport 5 years ago, seem insignificant at first, but can cause a cascade of consequences later on.

But not everything that happens in our life is the result of contingency. I don’t often say this – but some things are ‘destined to happen’. I am not talking about finding Mr. Perfect or Mrs. Right. I am referring to a different kind of destiny. A destiny that is shaped by our biology or environment, for example. A caterpillar in a cocoon will always emerge as a butterfly, not as a bumblebee or as a beetle. Whatever happened in its life as a caterpillar, this particular outcome cannot be changed. Similarly, someone born with one faulty copy of the haemoglobin gene will develop sickle cell anaemia. And whichever life I would have lived, I’d probably be great at growing a beard. Some tendencies are inevitable.

A butterfly emerges from its cocoon. No butterfly can change this outcome.

There is a tension between these two forces. Contingency is a random process. Yes – the future depends on the past, that past is full of ‘historical accidents’. All possible outcomes are rooted in random events. Inevitabilities, on the other hand, are non-random. They have a direction and impose limits on what is possible and what is not. This tension between random and non-random not only affects the course of our own lives, but also that of evolution itself. As a historical process, evolution should be subject to contingency. But we also know that evolution follows certain rules and laws – like natural selection. So how do these two forces play out in nature? To what extent is evolution random? This might look like a simple question, but it has divided some biologists deeply.

Contingency

One of the most passionate advocates for a contingent view of evolution was Stephen Jay Gould. In his book Wonderful Life he describes a famous thought experiment, where he imagines what would have happened if the asteroid that struck the earth 65 million years ago had missed it instead. The asteroid impact lead to the extinction of thousands of plants and animals, including all large dinosaurs. If the asteroid had flown by our planet, dinosaurs could have continued their rule over the earth. Mammals would never have flourished like they did after the original catastrophe. Perhaps they would have remained small and nocturnal creatures, destined to scrape by in a reptilian world. Gould thinks it is unlikely that humans, or human-like intelligence, would ever evolve in this alternate reality.

Devastating asteroids are historical events that are not part of any theory of evolution. Still such events have the power to change evolution’s course. Even the simplest mutation in a gene is historical event, because they are unpredictable and not predetermined. While biologists may now know some of the laws and forces that drive evolution, historical contingency prevents them from predicting its future. A biologist studying sauropods (‘long-neck dinosaurs’) 66 million years ago could never suspect that these successful, lumbering giants would become extinct one million years later for example. Just a small change in life’s history is enough change the world into one that is very different from the one we see today. Gould said this best himself:

We came this close (put your thumb about a millimetre away from your index finger), thousands and thousands of times, to erasure by the veering of history down another sensible channel. Replay the tape of evolution a million times from a Burgess beginning, and I doubt that anything like Homo Sapiens would ever evolve again. It is, indeed, a wonderful life.
~Stephen Jay Gould, Wonderful Life

The Burgess Shale that Gould mentions is a fossil bed from the Cambrian and forms the main inspiration for Gould’s argument. The creatures in the Burgess Shale were buried in an undersea mudslide around 500 million years ago. This sudden burial lead to the perfect preservation of these animals – even their soft tissues are immortalized in the rocks. The palaeontologists Simon Conway Morris, David Briggs and Harry Whittington reanalyzed and reconstructed many of the Cambrian fossils of the Burgess Shale. They found that many of the Burgess animals had bizarre designs. Animals like Opabinia, Aysheaia and Hallucigenia al have body plans that are so unfamiliar that they appear to be unrelated to animals of today. Even the not-too-spectacular Marrella doesn’t fit into any modern group. Marella has similarities to crustaceans and trilobites, but belongs to neither family.

The bizarre Opabinia, grabbing an Amiskwia with its proboscis.

Although they turned to stone a long time ago, these strange Burgess creatures still pose a burning question: why did they go extinct? Why can’t we buy a pet Opabinia in our pet stores? I’m sure aquarium hobbyists would love to get there hands on Opabinia – it would add some unique diversity to their aquariums, for the millions different species that are alive today only represent a handful of different body plans. A million different beetles are still a million variations on a common theme. From the ~20 different Cambrian arthropod designs present in the Burgess Shale, only four survived. Why only these four, and not another set? Gould thinks that it was sheer luck. We can’t really say why some species went extinct, he says. Their bauplan wasn’t ‘less adapted’ or ‘more primitive’ than that of their more lucky relatives. They were just different. It’s as if their fate was decided in a cruel lottery. But if you would pick a different set of lucky survivors, and marrelloids instead of crustaceans would have crawled around the floors of the sea. A small change in Cambrian times, but a radically different outcome.

Why can't we buy a pet Opabinia in our pet stores?

Convergence

Gould’s interpretation of the Burgess Shale is not uncontroversial. Two of the heroes in Gould’s book, David Briggs and Simon Conway Morris, criticized the theories of their admirer. David Briggs published a couple of papers that aimed to show that the Burgess creatures weren’t that morphologically diverse at all. But it was Conway Morris who challenged Gould’s claims on contingency in his book the Crucible of Creation.

When Simon Conway Morris looks back at the history of life, he doesn’t see randomness and contingency. He sees direction and convergence. Convergence is the observation that evolution tends to come up with similar answers when it is faced with similar problems. All animal lineages evolved eyes, for example. From the compound eyes of insects to the lens-bearing eyes of squids and vertebrates, each animal has found its own way to see the world around it. The form of the eye might vary, but having eyes seems to be a good rule of design. According to Conway Morris, evolution converges on a limited set of solutions time and time again.

Similar environmental selection pressures, acting on differing anatomies, can create convergent or parallel adaptations. [..] History is constrained, and not all things are possible. To understand how creatures that are descended from very different groups can evolve similar forms and functions, consider that dolphins, which evolved from doglike mammals, are shaped like fish because there exists an optimal shape for moving through water—a classic example of convergent evolution.
~Simon Conway Morris, “Showdown on the Burgess Shale,” Natural History magazine, 107 (10): 48-55.

There are only so many ways of moving around in water so dolphins are restricted in their options. Conway Morris doesn’t say that the specific from of a dolphin is inevitable. There are numerous differences between fish, ichtyosaurs and dolphins. Fish have gills, whereas dolphins breathe through a blowhole. Yet it is obvious that all these different creatures are shaped like a fish. Maybe ‘the form of the fish’ is the only logical endpoint for marine creatures with a spine. He argues that replaying the tape of life will give us a different, but very similar outcome. Yes – Marella could certainly have become the ancestor of a successful lineage of marine arthropods. But they would have filled the same niches as trilobites or crustaceans.

So where do we go from these two conflicting views? Is evolution guided by contingency, or convergence? It is important to remember that this is not an ‘either-or’ issue at all. Contingency and convergence are not mutually incompatible. It would be silly to say that evolution is free of constraints or predictable patterns. It would be equally silly to say that history plays no role in evolution. Contingency and convergence both shape the possibilities and impossibilities of evolution. Figuring how these forces are together weave the tapestry of evolution should be an exciting enterprise (and provide enough fuel for another blogpost).

Why then, do these questions incite so much debate? This is because deep down, they are not about dolphins and Opabinia. The question all of us want to find an answer for is whether the evolution of human conciousness was somehow inevitable. Many, including Conway Morris, think it was. I most recently came across this view in Kevin Kelly’s latest book, What Technology Wants. In this book, technology enthusiast Kevin Kelly goes as far as reversing Gould’s statement that ‘humans are an entity, not a tendency’ into the exact opposite statement ‘humans are a tendency, not an entity’. Convergence, Kelly says, drives life to become more complex and yes, more conscious. Twelve years ago, Gould already pointed out the weak point in this argument:

Evidence for convergence requires multiple cases of independent evolution, while the example that we all carry closest to our hearts (and that engenders the emotional oomph in this debate)—the evolution of consciousness in Homo sapiens—remains an outstanding singleton in the only history of life we know: the story of our own planet.
~Stephen Jay Gould, “Showdown on the Burgess Shale,” Natural History magazine, 107 (10): 48-55.

I have to agree with Gould here. In contrast to the repeated evolution of fishlike creatures, we have only know one example of a conscious creature evolving. It is impossible to claim that the evolution of consciousness is a something that has occurred repeatedly in the history of life. We should be open to the idea that we are here partly because of the inevitabilities that constrain evolution, and partly because we have been lucky enough that history unfolded as it did.

Many find this idea that mankind is not the inevitable outcome of evolution offensive. It rubs against our collective, human pride. Copernicus, Galileo and Kepler already showed us that earth is not in the centre of the universe. Darwin removed mankind from the centre of creation. The last retreat of our feeling of human superiority seems to be the thought that somehow, everything is meant to be this way. It is comforting to believe that the evolution of human consciousness is the fulfilment of a promise made 4,6 billion years ago. Because what would we be left with, if mankind turned out to be a fortunate accident?

I think we would be left with an even greater appreciation of the wonderful world in which we live. The unlikeliness of a conscious species arising to start talking and reflecting on its own place in this universe, doesn’t make evolution any less stunning or interesting. It makes it more so. Nemo Nobody said this better than me. When the journalist asks Nemo which of his conflicting memories represent the ‘right’ story of his life, he replies “Each of these lives is the right one. Every path is the right path. Everything could have been everything else and it would have had just as much meaning.”


Credits:
Butterfly photograph by Patrick Ronan.
Opabinia illustration found here, artist unknown. Please contact me if you are (or know) the original artist.
Ana and her pet Opabinia illustration by Glendon Mellow. Check out his site here.


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15 comments to We Are Nobody: Contingency and Convergence in Evolution

  • I’m with you – both biologically and philosophically, I’m totally for contingency.

    Love your writing here – it was really fun to read!

  • Lovely as ever Lucas.

    Your last little riff about the chancey-ness of our own evolution makes me think about projects like SETI and the way we generally think about the chances of other intelligent life in the universe. A lot of people (actually Richard Dawkins is one of them) seem to think that if life evolved on another planet then it’s almost inevitable that an intelligent species will pop up given enough time. Whereas I would have thought even if life is common in the universe there will be millions of times more planets without intelligent species than with.

    And I’m with you on the philosophy too! “You mean, just by chance I’m a member of the only species that is able to ask questions about its origins and I live at a time and a place in which I can spend a good portion of my life trying to answer those questions!” It’s like winning the lottery every day (except when your gels have no bands;)

  • Thanks David!

    The SETI question is a really interesting one. It remembers me of the first time I saw Carl Sagan scribbling down the Drake equation (no one can say BILLION like Carl)! Basically, the question about the inevitability of the evolution of intelligence boils down to estimating the fi parameter in that equation. I’m not sure if we will ever be able to resolve this dilemma fully..

    The other parameter of that equation that shouldn’t be ignored is the expected lifetime of intelligent life. Because even if the evolution of consciousness on this planet really was inevitable (to indulge Dawkins, Conway Morris and the like), a visiting extraterrestrial would have to visit earth in a very narrow window of time to encounter intelligent life. Even if they would recognize that the early hominids like Homo Erectus have the potential for consciousness, they would have needed to visit in a time window of 0,043% (2 million years of homo/4600 million years of planet *100) of our planet’s existence. At any other moment in time they would have encountered an earth that is covered with microbes or roaring with reptiles (those earths would be interesting in their own right of course!). If they would be looking for life that can communicate, the window becomes even smaller. Not that I’m not hoping that someone else is gazing up at the skies, elsewhere!

    Also: I pray the god of the gels starts giving you some bands soon ;)

  • Thank you for this post. As an evolutionary biologist who tries to identify whether evolutionary patterns are contingent, I very much enjoyed it. My only criticism is for the introduction part, you portray evolution as if it’s a set of choices of the organism, as if evolution has it’s own mind. Though later in your post it becomes apparent that you point the luck & randomness side of evolution. I guess it is always hard when we draw analogies from real life, such as a movie that is about choices…

    You may want to check out Richard Lenski’s long term evolution experiments, (especially the infamous 2009 PNAS paper) on a bacterial point of view on contingency vs. convergence.
    Thank you :)

    • Thanks for your comment Betul!

      As you said, for something as complex historical contingency, the perfect analogy probably doesn´t exist. There are many aspects to contingency, of which the ´butterfly effect´ (small change – big outcome) as seen in Mr Nobody is but one. But I’m glad I still got the randomness across in the later paragraphs though :)

      In some drafts of this blog post I included the Lenski papers, but as the drafts grew and grew I decided to save them for a later post. I figured I was already stretching the internet’s patience to the point of breaking with a post of 2000 words ;)

  • Awesome post Lucas! I had no idea what a great writer you were when I met you at #scio11. Kind of in awe. :)

    I started a weekly book club that’s reading GEB and at our last meeting we got into this topic on the evolution of consciousness and just basic issues of randomness vs. order. So I shared this post with the group. Thanks for writing it!

    • Thank you so much, that’s really nice to hear! It was great meeting you at #scio11, but reading each others writings (and in your case: listening to your music! which is awesome, by the way) really adds another dimension in getting to know each other.

      I’m also glad the post was of help. I never heard of GEB before, but it looks like an intriguing book to read. Even if its scope is a bit daunting ;). Wish I could join your book club!

  • Awesome!
    I just stumbled into your blog and immediately liked your style of writing.
    I’m actually a science blogger myself, and have written a very similar piece with the same books as references. :) Quite funny. My spinoff story was Terry Pratchett’s Science of Discworld instead of Nemo Nobody, though. And, of course, my piece was written in Finnish.

    • Your blog looks gorgeous Maija, such a pity I can’t read it! I would still love to see your Finnish blog post on the same topic though. Maybe Google Translate can brew something nice out of it :). I’ve never read the Science of Discworld, so I’m really curious to see how you introduced the topic.

      When I looked around your site I came across some of your art as well.. amazing! You’re really talented.

    • Thank you!
      I’m aiming to be a professional science writer some day, so I try to make my blog look good. :)

      Google Translate doesn’t work very well with Finnish, but if you want to try, the contingency vs. convergence article is here: http://planeetanihmeet.wordpress.com/2010/05/11/sattuma-ja-valttamattomyys-voiko-evoluutiota-ennustaa/

      In the Science of Discworld the wizards have Earth in a glass globe on their desk, and they can go in, change small things and direct history. I start by wondering if that would really be possible (assuming, of course, that one could travel in time) or if every minor change would direct evolution in completely different tracks that can’t be predicted, as Gould claimed.

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  • buddy childers

    I beg your pardon if I may be a bit overwhelmed with these interesting concepts. I am wondering if… We are Nobody = We are Somebody, but not Everybody. Isn’t it Somebody that has the contigencies that need to converge into what Somebody is interested in being? Perhaps that attempted convergence finds conflicts that seem very likely impossible to resolve such that Somebody can’t be Everybody, because we don’t know what that means, so we can’t “be” it.

  • buddy childers

    I beg your pardon again… as I hope I’m making some sense… at least for myself, because I feel my independent consciousness may have been raised with the reading of this article… which I recognize your consciousness may be perhaps superior… and I’m converging toward a better one myself. I am Somebody, but not Everybody… and I thought that Kelly’s point trumped Gould’s. To me, Nobody reflects Gould’s “entity”, while Kelly’s “tendency” reflects what I refer to as Somebody… with consciousness not destined to converge in the same direction, so to speak. Anyway, I feel this article has helped me understand the world a little better. Thanks so much, Lucas.

  • Hi Buddy,

    Thanks for your reply and compliments. The most difficult aspect of this debate is that both sides have good points. Evolution is not free from tendencies. If you would look at our ancestors one million years ago, maybe you could have predicted that some of their descendants (us) would become intelligent and attain consciousness. But saying that this tendency is inherent to life and evolution itself is a bridge too far, in my opinion. We are in part ordained, in part an accident. But mostly an accident, as far as I’m concerned ;).