"Without the evolution of locomotion there would be no sex, no photosynthesis, no ecology"
Q&A with evolutionary biologist Matt Wilkinson.
Most of us never think about how we get from one place to another. Yet the fact that we and other species are able to do this - to move through the world - is one of the great triumphs of evolution. In fact, to fully understand how life evolved on Earth, we must first understand movement. In his new book "Restless Creatures: The Story of Life in Ten Movements", evolutionary biologist Matt Wilkinson traces this four-billion-year history. Here, he discusses his arguments.
Restless Creatures argues that the true story of evolution is that of locomotion. Could you explain?
At first glance, locomotion may not stand out as particularly important, partly I think because we tend to take our own extraordinary locomotory abilities for granted - and they really are extraordinary. But moving effectively and efficiently from place to place is one of the most vital determinants of how many healthy offspring a creature leaves, which is all that matters as far as natural selection is concerned. Locomotion gets you to food, away from a predator, and at the very least will get your children away, where they're less likely to compete with you or each other. And the less energy you spend doing it, the more you've got left for baby-making. On top of this, moving well is difficult, and tends to exert strong constraints on the shape and behaviour of an organism - constraints that ultimately derive from the laws of physics. To give an example, the streamlining that has evolved again and again in big, fast swimmers is an obvious response to the need to minimise drag underwater. There's plenty more where that came from: our eyes, brain, left/right symmetry, backbone, opposable thumbs, even our emotions are all ultimately locomotory adaptations. Not even the apparently immobile plants are beyond its reach - trees and flowers are adaptations to enable effective dispersal of pollen and/or seeds. And without the evolution of locomotion there would be no sex, no photosynthesis (as bacteria would never have left the ocean floor and found the sunshine), indeed no ecology. Life without movement is just unusually complex chemistry. It's a big deal!
When did you get interested in looking at movement?
I became seriously interested in locomotion as I neared the end of my undergraduate studies, when I was getting into palaeontology in a big way. I was particularly enchanted with pterosaurs - the extinct flying reptilian cousins of the dinosaurs - and how they flew. It struck me that finding out about aerodynamics would give me a great way to understand what these creatures were like when they were alive, because it would be much easier to interpret the limited fossil remains in the light of the stringent demands of flight. But once I'd got used to looking at the physical nature of the living world I saw the marks of locomotion everywhere. It was very exciting - as if I was finally "getting" what life was all about.
How does this emphasis on locomotion square with Darwin’s theory of evolution?
It's completely consistent with - indeed derives from - conventional Darwinian theory. The basis of Darwinism is that, if there is variation in a population, if that variation is at least partly heritable, and if different variants have different fitnesses (i.e. reproductive success, depending partly on survival), then given sufficient time that population will adapt to its environment. What it doesn't say is why certain variants have higher fitness than others. That will of course depend on all kinds of aspects of a creature's biology and the context of its environment, but I'd argue that, more often than one might think, the key aspect - certainly the one that's most likely to influence a creature's form - is how well an organism moves or controls its movements. What's more, moving creatures are more likely than non-movers to encounter new environments, which might push their descendants down new evolutionary paths as they adapt to life and locomotion in the changed conditions. For instance, it was the movement onto land of our amphibian ancestors that initiated the explosive evolution of terrestrial vertebrates (backboned animals). If I wanted to stoke controversy, I might put this in different terms, pointing out that the inheritance of the environment (the extent of which depends on the dispersal capabilities of one's offspring) is every bit as important as the inheritance of the genome in determining what evolution can do; this means that the locomotory decisions made by an organism in its lifetime can have a tremendous impact on the long-term future of its lineage, assuming it survives. In a certain light, this line of thinking might have about it a whiff of Lamarckism, predicated on the inheritance of acquired characteristics, for we're not just a record of what our ancestors were, but what they did (especially where they went). But I hasten to reiterate that all this is completely consistent with Darwinism. It's just that there's more to evolution than genes alone!
How has locomotion affected human civilisation? In the book you talk about “wayfaring”, and separately about the impact on storytelling.
Well, just as our anatomy can't be understood unless in the light of movement, neither can our psychology be understood unless in the light of our desire for movement. This desire is writ large in the history of civilisation, with the domestication of horses and the invention of wheels, boats, trains, cars, rockets etc all pushing our locomotory prowess further and further beyond what our biology grants us. But it's arguably in the uncivilised - hunter-gatherers - that this desire finds its purest and, I would argue, its healthiest expression. Whether hunting or gathering, our ancestors had to do a lot of walking and running to survive, so it makes sense that our brains were genetically "programmed" to make us enjoy the act of moving, by activating those networks of brain cells that make us feel excited or satisfied. Given that it's been only 10,000 years or so since we began to turn away from such a lifestyle (a blink of an eye on an evolutionary timescale), we might expect this programming to be largely intact today, and there's plenty of evidence that this is the case. The runner's high is an obvious example of an emotional reward for locomotion, but so too is the thrill of exploration. Both seem to involve the secretion of dopamine, which is popularly conceived as the brain's "reward chemical".
This brings me to wayfaring. Wayfaring is locomotion that involves full sensory immersion - moving while paying full attention to one's surroundings - and it's one of the easiest natural ways to achieve a dopamine "hit". Modern hunter-gatherers do it all the time, and many anthropologists have commented on the tremendous sense of well-being and meaning that their journeys engender. That got me thinking. Wayfaring involves building a coherent, meaningful representation of your environment from the sequence of sensory 'snapshots' encountered along the way. Well, stories work in a similar way - we knit events together to build a meaningful narrative. I wonder if the joy we get from a good story might therefore come about because we're tapping into our ancient psychological apparatus for locomotion. It would be worth looking into.
You speak of the threat of locomotive technologies like the car. Could you explain how this threatens us?
Oh, in all sorts of ways! First, of course, there's the enormous death toll of traffic accidents. The WHO estimated that there were 1.25 million road traffic deaths globally in 2013, which is equivalent to 10 no-survivor aircraft crashes every day. How we tolerate this dreadful cost beggars belief. Many cars are also major contributors to dangerous air pollution, which is becoming an increasingly hot topic - just five days into 2017 London breached its annual legal air pollution limit. But every bit as troubling (to me at least) is the way cars influence how we relate to the places we live and to our own bodies.
Our vehicles seduce us with the promise of undreamed-of locomotory prowess, seeming to offer all the freedom of natural movement with vastly increased speeds and minimal personal energy expenditure. But this ease of long-distance movement has just led to a great scattering of the places we live our lives - in 2014 the UK Office of National Statistics calculated (based on 2011 data) that the national average distance from someone's home to their place of work was 9.3 miles and increasing. This geographical spreading of our daily existence is surely contributing to the increased fragmentation of communities and the rise in societal loneliness. And you can't really wayfare in a car - it's too fast, too dangerous and too constrained by road plans (and lately, satnavs). So few of us truly explore the places we live, making us more like fleeting occupants than true inhabitants (to paraphrase Tim Ingold's dichotomy), stripped of much of our locomotory agency. But even if we become aware of the negative impacts, opting out is so rarely practical, as our lives and settlements are now all too often expressly designed around the car. And the more we get used to our four-wheeled exoskeletons the feebler our own bodies seem to be: distances of a few miles - undoubtedly trifling to our hunter-gatherer ancestors - are often viewed as unwalkable these days. We've become addicted to cars as a society, and while the rewards diminish as traffic density increases, the symptoms grow ever worse as we get fat, unfit, frustrated and disconnected.
What do you think is next for humans, evolution, and locomotion, given that we live in this technology-dominated landscape?
Making predictions about our long-term evolutionary future is a perilous exercise, but I'd like to think that the current trend of outsourcing our locomotory capabilities to our machines will eventually come to an end. Surveys are finding quite high levels of discontent among drivers, and already some governments are taking steps to chip away at the four-wheeled hegemony. For instance, Amsterdam, Copenhagen and Bogota are notable for their cycle-friendly designs, and plans are afoot in Helsinki to make private cars obsolete in the city by 2025. Deep down I think we still love to explore the world under our own steam, as we all did when we were children. Just look at the recent success of Pokemon Go, which tapped in to this latent craving. Barring some dystopian nightmare when babies are installed in mini-cars before they learn how to walk, I think our descendants will be spared the fate of Wall-E's morbidly obese, skeletally impoverished, pitifully infantilised humans!
What are the challenges in writing about science and evolution for a general audience?
I guess the obvious challenge is making complex information understandable to people with little or no background in the topic in question. But that really just requires a bit of empathy on the part of the writer - the ability to step back and imagine you know nothing about this process or phenomenon, so you can build a picture of it from the ground up. People can understand anything if it's explained properly. The real challenge is writing in such a way that the reader wants to keep on finding out. That takes far more than the ability to explain - you need to tell a compelling story, and one that may not have a human protagonist with which the reader can relate. How you frame the science is therefore every bit as important as the science itself. You have to take the reader on a journey - a cliche but, under the circumstances, a fitting one.