In which fangirling turns into philosophy

Textbooks may portray science as a codification of facts, but it is really a disciplined way of asking about the unknown. — Andrew Knoll, Life on a Young Planet

Some books change your life. When I was 12 or 13 or thereabouts, SJ Gould and others’ Book of Life rekindled my interest in prehistoric life, introduced me to the Cambrian explosion, and opened my eyes to a whole new worldview. It’s one of the reasons I hold a degree in evolutionary biology.

Life on a Young Planet was not a life-changer, precisely. That’s not why I love it to pieces. By the time I read it, I’d gained an appreciation of just how complex and full of uncertainty natural science was, and the book was permeated by an awareness of this complexity. Also, it was simply beautiful writing.

(I can’t emphasise the importance of good writing enough. I’ve read too many papers and books [Crucible of Creation and The Plausibility of Life, I’m looking at you] that had good information but were so atrociously written that I nearly put them down despite being fascinated by their subject.)

Last month, the author of Life on a Young Planet, Harvard professor Andy Knoll, came to visit my university. I was practically bouncing with excitement from the moment I saw his name on a newsletter. He gave four lectures in total; until the very last one, I actually contemplated getting my copy of the book signed. Or, to be a fangirl and a nerd, my printout of his lovely biomineralisation review. (I still can’t decide if I made a mistake. Damn, I didn’t even ask a stupid question. Four lectures, and I just sat there and drooled over my notebook.)

Knoll is nearly as good a speaker as he is a writer. He doesn’t have the liveliest voice and speaks quite slowly, but if you can get past that, his lectures are really good. (I’m glad of that; I really don’t like losing my illusions!) They are solid structures that you have no difficulty following the logic of.

Let me put it this way – Andy Knoll is an excellent storyteller.

That got me worrying, because I’m a sceptic and (truth be told) a little bit of a cynic at heart, and because over the years I’ve done a lot of navel-gazing about belief and knowledge and conviction. I have a tendency to grow suspicious when I feel too certain about something.

Am I – are we – too often blinded by good storytelling? How often do we get so enamoured of good ideas that we try to force them on situations they don’t fit? And how often do we doubt something just because it sounds too neat?

Here’s the specific example from the Knoll lectures that made me think of this. Knoll is a champion of the oxygen + predation explanation of the Cambrian explosion. (I didn’t realise he was involved in that paper until it came up in the lectures…) He is also an advocate of a similar explanation for the diversification of single-celled eukaryotes 250 million years before the Cambrian. He convinced me well enough, but then I immediately thought – really? Is it really that simple? Does one size really fit both events?

I often take note of these “pet ideas” as I read scientific literature. A group of phylogeneticists uses microRNAs to tackle every tough problem ever. A palaeontologist interprets every squishy-looking Cambrian weirdo as a mollusc. Researchers in the biomineral field look for slushy amorphous precursors to crystalline hard parts everywhere. (Remember, all generalisations are false ;))

Just to be clear: I’m not at all saying that being a “pet idea” automatically makes something wrong or suspicious. For instance, the hunters of amorphous biominerals have some good theoretical reasons to look, and they often do find what they’re looking for. Likewise, I’m impressed enough with Andy Knoll’s pet hypothesis about the Cambrian that I’ve rethought my own pet ideas about the subject.

I’m also not accusing these people of being closed-minded. Going back to Knoll, IMO he demonstrated ample healthy scepticism about his pets during his post-lecture Q&A sessions. (Which makes me a bit less nervous about the neatness of his stories.)

Someone better versed in the philosophy and sociology of science could probably write a long treatise involving paradigms and confirmation bias and contrariness here. I’m even less of a philosopher than I am a geologist, so I think I’ll leave the deeper insights to those who have them.

Meanwhile, I’ll continue to be a fan of Andy Knoll and appreciate a good scientific story. So long as I remember to look beneath the surface – both of good stories and of my own suspicion of them…

 

Mini-rant: BBC, oh please!

I love BBC documentaries. I also used to love the books of David Attenborough’s BBC documentaries (I never watched those. I know, shame on me.). They tend to have the same sense of wonder that drove me to natural science, and which is lost in a number of other documentaries I’ll refrain from naming for now.

I understand that you can’t show all the subtleties and uncertainties and bloody wars over pet hypotheses that characterise cutting-edge science in a work aimed to entertain as well as educate the public. To tell a coherent and engaging one-hour story, you must simplify.

That doesn’t mean your story has to be bullshit.

(FWIW, my first beef is with the title of the film. It’s called First Life, but it gallops through the 80% of life’s history that didn’t involve animals in like the first ten minutes of the two-hour run time. But I digress.)

You see, in the first part, we get a nice lead-up to the Cambrian explosion, starting with Snowball Earth, the origin of multicellularity, animals (enter sponges), body plans (enter Ediacaran creatures), and so on. At some point, there is some musing about how complex animals began to diversify and adapt to new lifestyles, and it’s brought down to… the increased genetic variation provided by sex.

(ETA 120121: I should clarify, because I was having a bit of a brain fart when writing the original rant. The Marinoan glaciation, where my Snowball Earth link leads, is NOT the last big glaciation before the advent of animals. That honour would probably go to the Gaskiers glaciation, which I’d completely forgot was later than the Marinoan – roughly the same age as early Ediacaran fossils, in fact. Nonetheless, Wikipedia reassures me that the Gaskiers was not as severe as hardcore snowball events like the Marinoan.)

It’s pretty clearly implied by the narration that animals began to reproduce sexually around the time they started moving about and having heads and tails and similar complexities. If you paid attention to the story they were telling you up to that point, you can come away thinking that earlier animals didn’t get it on. (Like sponges don’t???)

The only problem with this is that it’s 99.999% certainly, utterly, and obviously, wrong. Sexual reproduction[1] is an ancestral feature of eukaryotes, that is animals, amoebae, malaria parasites, plants, algae of all sorts, fungi, slime moulds, paramecia, etc. etc. (name your favourite protist).

Animals do it in fundamentally the same way, using fundamentally the same molecular machinery as other eukaryotes. And there is every indication that they always practised it. Sponges do it. I’m willing to bet that every major animal group does it. Sure, many animals are also quite happy to reproduce by budding or falling to pieces, but most of them are at least capable of sex. Very little is known about the life of our closest non-animal relatives, but the sexy genes are there.

So, um, that exciting story you were telling us about how sex changed everything? Doesn’t work. I suspect that the whole nonsense was stuffed in so that they could show off this cool find, but can’t you talk about the earliest evidence for animal sex without making it sound like something it isn’t?

Hrm. That kind of unmade my day. Now I worry if the same level of crap gets into the other documentaries I loved so much, and I just didn’t spot it because I’m not a physicist/mathematician/historian/insert profession here. Ah, the joys of being an insufferable pedant and watching films about stuff you actually have a passing acquaintance with…

[1] basically, the making and fusion of sex cells. Everything else, from testicles through frog hugs to intercourse, is just embellishment.

The folly of hindsight

Recently, I’ve been re-reading Life on a Young Planet. As I said before, it’s an excellent book. It is beautifully written, cleverly structured, and the author is obviously knowledgeable about the subject (which, sadly, isn’t always true in popular science). Most importantly, it emphasises the process of science, as opposed to the actual knowledge gained through that process. “How do we know what we know?” is a question at least as important to Andrew Knoll as “What do we know?” As he so eloquently puts it, “[t]extbooks may portray science as a codification of facts, but it is really a disciplined way of asking about the unknown.” This is an attitude I share with him, and probably a big part of the reason the book has such a special place in my heart.

So, I was surprised to discover on this re-read that Knoll falls into one of the most common traps of talking about evolution: teleological thinking. In Chapter 11, “Cambrian Redux”, he writes that “[f]orty million years after the Cambrian began, evolutionary way stations still played a major role in the ecology of marine environments.” He is discussing the Cambrian explosion, of course, and here he is talking about stem groups of living phyla living alongside the crown groups [1]. I don’t think he means to convey a sense of goal-orientation, but the wording does exactly that. It sounds as if, say, Anomalocaris was just something evolution had to pass through to get to arthropods, not a successful animal in its own right. It suggests that the eventual supplanting of these now-extinct lineages was meant to happen.

Richard Dawkins called this “the conceit of hindsight” and complained about it at length in the introduction to his (also really good) book The Ancestor’s Tale. Dawkins characterises such thinking as “seeing the past as aimed at our own time, as though the characters in history’s play had nothing better to do with their time than foreshadow us.” (In this particular case, he’s talking about ordinary history, as a prelude to introducing the same problem in evolutionary history.) It’s a very common way of thinking about evolution (just look at any of the traditionalmarch of progressimages), and it’s also totally wrong.

If you’ve been in prolonged contact with creationists, you’ve almost certainly encountered conspicuous examples of this common misconception. Types of questions I’ve personally seen include “what use is half a wing/[insert transitional feature here]?”, “why didn’t all X evolve into Y?”, and “how did X know they were evolving into Y?” At the heart of each lurks the idea that evolution works towards goals. That it doesn’t seems to be one of the most difficult aspects of evolutionary theory to grasp, and it’s especially hard to escape when we are looking at the past.

Simply put, evolution has no foresight. Rather than working towards something, the process always reacts to something. Rather than looking ahead, it constantly lives in the present, though it’s often saddled with the baggage of the past. The kinds of things that cause mutation (such as replication errors, radiation and chemical damage) have random effects [2]. Moreover, the processes that sort among mutations, such as natural selection, are similarly blind. Because the mechanisms of evolution are not thinking entities, the only traits that get passed on are traits that help their owners reproduce in the here and now. Any long-term trend is the outcome of repeated rounds of selection on the same traits. Evolution has no goal in the same way a snowflake doesn’t aim for your nose, though in retrospect you can perhaps reconstruct the path it took to get there.

That’s the problem with history: we are looking back on processes whose outcomes we already know. It’s so tempting to view the preceding events as mere stages in a journey aimed at those outcomes. After all, we humans work with goals in mind all the time (ironically, nowadays we might use evolutionary principles to attain those goals!). Unfortunately, viewing evolution in this way can lose sight of the process by focusing on the endpoint – and then people start asking about half wings.

It’s important to remember that the ancestor of the wing was not “half a wing”. It was just a modified arm that had some advantage over its ancestor, e.g. large feathers to help a dinosaur keep her eggs warm, or (closer to “wingness”) glide from tree to tree. These animals weren’t half-functional fliers, they were fully functional at whatever they were doing. If an alien scientist looked around in a Middle Jurassic forest, it might have marvelled at the exquisite gliding adaptations of small dinosaurs much like Microraptor [3], but it surely wouldn’t have focused on how bad they were at flying.

(Also, always remember that when you are the only one who can do something, by definition you’re the best at it!)

I wish we could just drop the teleological language altogether. It’s surprisingly difficult even when you actively try, though. It could be something about the way language works (at least the two I know well). Somehow, it seems much easier to say things like “X evolved to do Y” in them than to give a more accurate description of the evolutionary process. I’m sure that says something profound about human minds…

***

[1] In systematic jargon, a crown group is the last common ancestor of all living members of a group, and all of its descendants (including extinct ones). The corresponding stem group (stem groups are always relative to a crown) includes anything extinct that’s more closely related to the crown group in question than to any other living lineage. For example, all non-avian dinosaurs were stem birds.

[2] We have to be precise about the meaning of “random” here. Some mutagens cause very specific mutations. “Random” refers to their fitness effects, not the chemical changes that happen or even the places where they happen (though the latter is largely random, except for trivial constraints). The same mutation in different parts of the genome can be beneficial, harmful or have no effect at all, and conversely, the same is true for different mutations at the same spot – and all of this is uncontrollable. If you keep your study organisms in a hot environment, they won’t suddenly start producing more mutations that make them heat-resistant. That’s the main thing we mean when we say mutations are random.

[3] Microraptor itself is Early Cretaceous – birds were already around when these guys inhabited the forests of China. The first part of the Jurassic – i.e. the time between early dinosaurs and Archaeopteryx – doesn’t have a great record of dinosaur fossils, so most of what we know of the origin of birds comes from relatives of birds that persisted alongside birds later on. However, a few very bird-like fossils are contemporaneous with, or older than, Archaeopteryx. Like Microraptor, some of these creatures have long leg feathers (unlike Microraptor‘s, theirs aren’t very aerodynamic) , so that may be something ancestral for the “birdy” lineage.