Taking Flight E-Book

Lev Parikian

• Herausgeber: Elliott & Thompson
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch
• Veröffentlichungsjahr: 2023

Seitenzahl: 409

Beschreibung

*SHORTLISTED FOR THE ROYAL SOCIETY SCIENCE BOOK PRIZE 2023* 'This book soars… Parikian is a nature writer at the top of his game.' Steve Brusatte, author of The Rise and Fall of the Dinosaurs This is the miracle of flight as you've never seen it before: the evolutionary story of life on the wing. A bird flits overhead. It's an everyday occurrence, repeated hundreds, thousands, millions of times daily by creatures across the world. It's something so normal, so entirely taken for granted, that sometimes we forget how extraordinary it is. But take that in for a moment. This animal flies. It. Flies. The miracle of flight has evolved in hugely diverse ways, with countless variations of flapping and gliding, hovering and diving, murmurating and migrating. Conjuring lost worlds, ancient species and ever-shifting ecologies, this exhilarating new book is a mesmerising encounter with fourteen flying species: from the first fluttering insect of 300 million years ago to the crested pterosaurs of the Mesozoic Era, from hummingbirds that co-evolved with rainforest flowers to the wonders of dragonfly, albatross, pipistrelle and monarch butterfly with which we share the planet today. Taking Flight is a mind-expanding feat of the imagination, a close encounter with flight in its myriad forms, urging us to look up and drink in the spectacle of these gravity-defying marvels that continue to shape life on Earth. '[Lev Parikian] brings a sense of infectious enthusiasm to his account of the evolution of flight in the natural world, from mayflies and bees to bats and hummingbirds by way of pterosaurs and archaeopteryx, combining a wealth of information with a sense of wonder.' The Observer 'This accessible account of the animal kingdom's development of flight exhibits a layman's enthusiasm for an everyday wonder.' Rebecca Foster, TLS

Leseprobe

‘This is a soaring, joyful book, filled with the wit and wonder of aerial gymnastics, deep time, evolution and biology. It might just be the nearest thing to flight in a literary form.’

Patrick Barkham, author of Wild Green Wonders

‘Lev Parikian illuminates one of the most magical mysteries of the natural world: how birds, bats, and insects break the bounds of Earth and fly through the heavens. His prose is every bit as buoyant as his airborne subjects. With the conversational chops of a storyteller and the authoritative expertise of a scientist, Parikian is a nature writer at the top of his game.’

Steve Brusatte, author of The Rise and Fall of the Dinosaurs

‘Witty and enlightening. This book may not give you wings, but it will give you a deep appreciation for all those animals that glide, soar, hover and flutter . . . and penguins.’

Helen Pilcher, author of Life Changing

‘A beautiful concept, flawlessly executed, Taking Flight is among the most charming popular science books I’ve read in years. Parikian is fast becoming one of the finest science writers out there.’

Jules Howard, author of Wonderdog

‘Lev Parikian explores one of nature’s most astounding evolutionary conjuring tricks . . . A work of clarity, levity and joy.’

Caspar Henderson, author of A New Map of Wonders

‘Whether you’re an engineer, a linguist, a historian or just curious, this book has something for you. It explodes with fascinating titbits, all delivered with a gentle touch of humour. Get ready to be swept away by the expertly crafted harmony of Taking Flight.’

Professor Lucy Rogers, author of It’s ONLY Rocket Science

‘Lev Parikian has produced a clear, crisp and entertaining account of the history of animal flight. A delightful and insightful read.’

Dominic Couzens, author of A Bird a Day

‘Lev Parikian’s writing – about the extraordinary wonders of flight – is as magical and uplifting as the aerial dynamics of our tiniest insects and birds.’

Ann Pettifor, author of The Case for the New Green Deal

‘Had P. G. Wodehouse ghost-written Attenborough’s Life on Earth, we might have had Taking Flight forty years ago. This is a charming book, which – like its author – fizzes with erudition, wordplay and humour.’

Nick Acheson, author of The Meaning of Geese

‘Taking Flight is full of wonders, large and small, and Lev’s own sense of the astounding fact of flight will make you look at the world differently. Those of us who can’t distinguish a pigeon from a pterosaur will learn lots, but it’s also bang up to date and informed by research. Brilliant stuff – I’m already planning to press copies on friends.’

Chris Lintott, University of Oxford

‘This book is fascinating – packed with “well, I never!” and “who’d have thought?” lines which you feel compelled to share. Beautifully written with characteristic warmth and humour, Lev somehow manages to explain the mechanics of flight in glorious detail without dispelling the miracle and magic of such a feat.’

Brigit Strawbridge, author of Dancing with Bees

To Winter.

Cat of cats, occasional keyboard sitter, and xcsgasxvbzx.

CONTENTS

Author’s Note

Introduction

1   The Mayfly

2   The Dragonfly

3   The Beetle

4   The Fly

5   The Bee

6   The Butterfly

7   The Pterosaur

8   The Archaeopteryx

9   The Penguin

10   The Goose

11   The Hummingbird

12   The Albatross

13   The Pigeon

14   The Bat

Afterword

Acknowledgements

Notes

Selected Bibliography

Index

AUTHOR’S NOTE

In this book I attempt to share some of what I have learned since the idea of a book about flight came into my head. I am an enthusiastic layman, only too well aware that in tackling the subject I am encroaching on areas both way above my pay grade and the specialist subjects of people far more qualified than me to write about them. I have come to some of these subjects completely cold, like an eager first-year student primed for knowledge. Inevitably, what I have learned is far outweighed by what I have still to learn. I am indebted to the many people who have devoted their lives to the subjects covered in this book, and whose work has inspired and educated me in its writing. I attempt to acknowledge all sources of information.

It’s my hope that I’ve written about this fascinating subject in a way that will place the reader in the ‘sweet spot’ – somewhere between reeling from too much information and tutting at the banality of it all. If I fail, I can only apologise to everyone. Please try to bear in mind that I meant well.

All mistakes are, of course, my own.

INTRODUCTION

A January Friday. Cold, grey, bleak. A day for buttered malt loaf and window staring.

It’s a typical garden scene. Grass, borders, fences, shed. Bird feeders, primed. My eye is caught by a quiver in the hazel. Quiver becomes rustle, rustle becomes blue tit, hopping up to an outer branch, checking for danger. Alert, always alert. It flies up to the feeder, flicks its tail, turns, pecks, turns again, pecks again. Another flick, back to the perch, check for danger, and off it flies, over the fence and away. Whizz, whirr, flurry. Ten seconds later and I would have missed it.

It’s an everyday occurrence, repeated hundreds, thousands, millions of times daily. Blue tit’s gonna blue tit, and I’ll always watch. They’re active birds, constantly on the move. Agile, acrobatic, endearing – all three at once when they’re hanging upside down from a bird feeder. But from this brief encounter one thing stands out.

It flies.

It. Flies.

It’s a thing so normal, so entirely taken for granted, that we forget how extraordinary it is. Our planet has gravity strong enough to draw objects of mass towards its centre – to defy that in pursuit of an aerial life seems needlessly perverse. It’s a notoriously difficult thing to do.

The trick, as Douglas Adams so neatly put it, is to throw yourself at the ground and miss.

Humans are terrible at it. We manage the first bit well enough, but it’s the missing that causes problems. Gravity’s a bugger that way. But this hasn’t stopped us trying. Human history is littered with the bodies of those whose ambition to fly has been brought crashing down to earth – literally and metaphorically – by harsh reality. For centuries the best we could hope for was a kind of mitigated plummet.

But while our bodies are ill suited to staying up in the air, our brains are good at problem-solving. A comparatively short time after our emergence as a species we came to understand that the ways of the air, while complex and invisible, are quantifiable, and that we might be able to exploit them to our advantage. And, crucially, we got good enough at technology to make machines that could help us realise our dreams.

And so we managed to haul our stubbornly unaerodynamic bodies into the air, and – and this is the important bit – keep them there. We’ve been doing it for well over a hundred years now, and we’re pretty good at it. With the help of technology, we can swoop, glide, hover, dive, climb, soar, float, drift and – if so inclined – slip the surly bonds of Earth and touch the face of God.* We can fly high and low, fast and slow, round the world and back again. Thanks to flying machines, our world has changed.

But still an inconvenient truth remains: without artificial aids we are drawn by the laws of physics back to the ground. Even though we have used our oversized brains to devise ways round this fundamental inadequacy, put us in a flying race against a mosquito or a beetle or even that reluctant last-resort flyer the red-legged partridge, and there will only ever be one winner. When it comes to telling the story of flight in the animal kingdom, we must – sorry, Icarus – allow others to take centre stage.

While many species, for various reasons, remain earthbound, plenty of others happily spend between 1 and 99 per cent of their time in the invisible medium we call ‘the air’. Unknowns being what they are, it’s difficult to deal with exact numbers, but of the more than 1.5 million described animal species on this planet, the vast majority have the gift of flight.

I suspect we don’t think about this enough. What would happen if we spent more time looking up, drinking in the spectacle of an animal defying gravity, and thinking about how this came to be, what it means, and what a wondrous thing it is to fly? At the very least, it would divert us for a few seconds. And we might imagine ourselves in their place, might strive to abandon for once our narrow, limited view of the world, see it from a different perspective. An exercise in empathy, an attempt to find within ourselves the capacity to be, however temporarily, something else.

The ability to fly seems miraculous to those not endowed with it, but a miracle is something that breaks the laws of nature – while flight is indeed awe-inspiring and envy-inducing, it sticks to the rules. The principle is in fact remarkably simple: four forces – lift, thrust, weight and drag* – combine, to the advantage of the aspiring flyer. Produce enough lift and thrust to counteract the weight and drag, and off you go. But the more you explore the subject, the more complex and involved it all gets, and the more accurate that word ‘miracle’ seems.

None of this worries a flying animal in the least. A pied wagtail, bouncing merrily over my head on West Norwood High Street with a cheery chizzick!, isn’t thinking of wing loading or aspect ratios or any of the other concepts that govern its capacity for merry bouncing. It just does it, in the same way that I, when catching a cricket ball, am not doing differential calculus to work out the ball’s trajectory. I merely catch it.†

The pied wagtail’s insouciance is replicated manyfold in its avian peers. From the ridiculous agility of a hummingbird to the powerful grace of an eagle, the freedom that flight represents is most readily observable in birds. Of the planet’s other flyers, insects are small, bats fly at night, and pterosaurs are extinct – but birds are right there, flaunting their ability for all to see.

There are many reasons to love birds – their featheriness, their behaviour, the fact that they’re dinosaurs. But at the heart of it is flight. As a child, I loved birds without understanding why; as an adult, I realised that flight played a large role in my obsession. This was in direct opposition to my own relationship with being in the air. For a long time flying fell into the same category as rugby: I was a keen observer, but an extremely unwilling participant. While it gave me pleasure to watch a great tit flitting from tree to feeder or swallows hawking midges from the surface of the local pond, my own forays into the air were fraught with nerves. It took me many years to embrace flying as an acceptable form of travel. Only gradually did I understand my own fear, realising that it wasn’t flying that scared me. On the contrary, I was captivated by the feeling of being suspended high in the air, seeing the world laid out in miniature below me. It brought a sense of freedom that transcended the inconvenience and discomfort associated with being trapped in a thin metal tube. I wanted little more than to dispense with the material of the aeroplane and engage completely with the flyingness. It wasn’t being in the air per se that gave me the heebie-jeebies. No, what I was afraid of was the idea of transitioning precipitously from flying to not flying.

In other words, I was terrified of crashing. And I didn’t anticipate the pre-crash plummet too keenly either.

Over time I learned to take a more rational approach to this phobia, and in doing so I began to think about flight in all its manifestations, and to delve into what it means to flyers and non-flyers alike. Once you start thinking about the extraordinariness of flight, it’s difficult to stop. Difficult, too, to quell the urge to grab passersby, point at the carrion crow rowing gamely through the air, and yell, ‘Look! Look! It’s flying!’

Curiosity piqued by the wonders of avian flight, I was soon asking questions about all the other flyers. How do hoverflies hover? Why are bats the only flying mammals? What does a daddy-longlegs actually achieve with its frankly pathetic, gangling excuse for flight? How and why and when did all this airborne nonsense come about in the first place?

This last question, the question of ‘when’, necessarily involves some delving into the issue of ‘geological time’, a subject apparently designed to induce giddiness. Perhaps this is because true understanding would demand we acknowledge how utterly tiny we are, and I don’t think humans are very good at that. The idea of ten years is manageable – we can remember what we were doing ten years ago and can at least have a stab at predicting what we might be doing in ten years’ time. A hundred years, while more than most people’s lifetimes, is still touchable – a matter of a few generations. A thousand is conceivable – think William the Conqueror and so forth – but requires some imagination. Ten thousand is familiar as a number because it’s how long agriculture’s been around, but try to touch it and we find ourselves groping in the dark. And as for a hundred thousand years – nope. A million? That’s one hundred spans of agriculture; three and a bit times longer than Homo sapiens has been around; or, if you find it easier, ten nopes.

And yet a million years, in geological time, is relatively small beer. Take the lifespan of this planet. If I were to represent this time frame – four and a half billion years, give or take – using a scale of a million years per page, this book would be 4,550 pages long. The first 500 pages, it has to be admitted, would lack interest for the student of life,* although the true enthusiast might gain a certain amount of pleasure from contemplating the texture of the empty pages. But gradually marks would appear, each one representing a life form. Small marks, indecipherable at first, eventually coalescing into letters, words, sentences, paragraphs. And soon each page would be seething. At about page 4,200, the first animal flies. Humans turn up in the last paragraph of the last page.

A gimmick it might be, and I would certainly fail to persuade my publishers – obsessed as they are with such trivial concerns as the cost of paper and the practicalities of producing a four-and-a-half-thousand-page book – that the symbolism would be an important part of the storytelling. But it would be. That physical representation might help us overcome the vertigo brought on by the idea of huge, unimaginable tracts of emptiness.

Add to this the question of geography. It’s easy to think about the world before we came along as existing not just somewhen else, but somewhere else too. Our brains, faced with the fatal combination of impossibly large numbers and the accompanying realisation of our own insignificance, melt a bit round the edges and refuse to cooperate. On coming across a fossil at the beach, we can cognitively understand that this is the preserved body of something that lived a very long time ago, but just as freaky, in my view, is the idea that it was here. Exactly here, where I’m standing right now.* This all happened in our world, and it is amazing.

Those fossils, for all their abundance, give us only the tiniest slice of information about how life grew on this planet. Although there are frustrating gaps all over the place, the existing record has enabled Very Clever People with infinite patience and a taste for puzzles to piece together what happened. Or might have happened. Or ‘could plausibly have happened and let’s leave it in the box marked “possible” until something better comes along’. Because that’s how it tends to work. Scientists construct hypotheses based on the best available evidence. The responsible ones generally shroud these hypotheses with caveats: ‘we think’, ‘it seems’, ‘one possibility is . . .’. And then another piece of the puzzle is found and it either confirms what they thought (hurrah!) or contradicts it (boo!) or makes the whole picture even more confusing (huh?). In some cases the body of evidence is strong enough to be considered fact, or near as dammit. In others it is frustratingly scant, and intelligent hypothesising is the order of the day. It is on this hypothesising that much of our understanding of evolution, and particularly the evolution of flight, is based.

Take yourself back a few years. Four billion should do it. At the bottom of the ocean, in the bubbling and roiling warm water of a hydrothermal vent, a microbe lives. That microbe is known as LUCA – Last Universal Common Ancestor. LUCA is not the first thing to live, but it is our most recent ancestor – where ‘our’ means ‘all life on Earth’s’. Strange though it might be to think of a piece of seaweed as our cousin – or a moss or an earthworm or even a trilobite (RIP) – that is the long and the short of it. Impossibly distant cousins, but cousins nevertheless. All life on Earth is related. We forget that all too easily.

From LUCA came other things. Then others, and others. And on it went, in agonisingly slow increments, developing and diversifying and changing. At any point, life could have taken a different route, diverted by different conditions, different circumstances, pure chance. Replay the story a thousand times, a million, a billion, and each time the outcome would be different. In those many possible iterations of this planet’s history, would there be flight? Would something at some point, somewhere, somehow take to the air? You’d like to think so. But the thing to remember is this. Flying is hard. Some creatures do it so well we’re fooled into thinking it’s easy. But for all of them – even those so well adapted to the challenge that they can stay airborne for what we consider serious amounts of time – what it does require is constant work. Sustained, coordinated and concentrated work. Without that, a flying thing turns into a falling thing, locking horns with gravity and losing.

Flight has evolved four times. That is to say, powered flight – the act of propelling yourself into the air and staying there. Strictly speaking, flight is a continuum. Anything that spends its time at least partially airborne belongs somewhere on it. The main thrust of this book is at the powered end of that continuum. Gliding, parachuting, falling with style – they’re all impressive in their own way; but flying – that’s something else.

Those four evolutions of flight occurred (as far as we know) in four distinct groups of animals: insects, pterosaurs, birds and bats. And in each of those groups the ability enabled success. The diversity of species adopting it is testament to its usefulness. Fruit flies and pterosaurs are wildly different animals, but they are united in their ability to throw themselves at the ground and miss. An exclusive club of miraculous exploits.

The club’s members outnumber the non-members. This is largely thanks to the extraordinary diversity of insects. How many species are there? Add to the 1.5 million described species all the others we either haven’t found or named yet, and estimates range from 2 to 30 million, with 5 million considered by many a reasonable guess. Throw in nearly 11,000 bird species and just over 1,400 bats, as well as all the extinct species in every category (including at least 200 pterosaurs), and we quickly reach numbers every bit as bewildering as those associated with the enormity of geological time. And most of them fly.

From those millions of animals I have chosen fourteen. The choice is, to an extent, guided by personal preference. I’ve already mentioned my love of birds, but the inclusion of six of them in the fourteen isn’t just favouritism – they exhibit more variety in the way they fly than any other group. Also abundant in the list are insects, the first animals to take to the air. The six I’ve chosen represent not just their evolutionary history, but the various bodily adaptations that have enabled their extraordinary success. Completing the list are pterosaurs – standing alone as the only completely extinct flying group – and bats, our closest flying relatives and the only flying mammals. Between them, these fourteen representatives chart the chronological and evolutionary history of flight, represent its various uses, and illustrate the different mechanisms and body plans by which it is achieved. Some – hummingbirds, dragonflies and bats, for example – do it with extraordinary agility; others – albatrosses, bees and geese, say – have particular specialities; and some – mayflies, beetles and particularly the bumbling Archaeopteryx – represent the ‘inexpert but perfectly useful for our current needs, thanks very much’ corner of the clubhouse. There’s space, too, to consider what happens on the rare occasions that flying animals relinquish their superpower and join the rest of us back on the ground.

We start, as you might expect, at the beginning.

* ‘I have slipped the surly bonds of Earth . . . and touched the face of God’, from ‘High Flight’ by John Gillespie Magee Jr.

* Loosely: lift – upward; weight – downward; thrust – forward; drag – backward.

† Or, more often these days, drop it.

* There was of course a huge amount of geological activity going on, but that is not our concern.

* One does of course have to allow for the shifting of landmasses that has occurred over those periods, but I hope you’re with me in the basic concept.

1

THE MAYFLY

Take yourself, if you can, to a stretch of clean, fresh, flowing water. It will be a spring day. There will be, if you get it right, warm sunshine. And the place will have an air of tranquillity, such as might inspire feelings of well-being in the human soul. The trickling of water, the swish of reeds, perhaps even the gentle susurration of wind in willow branches. Birdsong will probably fill the air. It often does. Everything combines to give the scene an indefinably timeless quality. You’ll sit awhile, allowing time to ooze by. You will have left your phone at home (because you’re sensible), so all you have to do is relax, observe and wait.

It might be a flickering out of the corner of your eye, a fracture in the continuum. Or perhaps there’ll be a disturbance on the water’s surface, a small splash. And then another. And over there, another. And before you know it the air is full of activity, whirring specks of fluff caught in the sunlight, a seething cloud of them, so profuse that even when you try to follow the flight of an individual it is quickly absorbed into the general melee. And meanwhile the trout pop to the surface and gorge themselves, relishing the sudden appearance of a free buffet.

The mayflies are emerging.

As you sit by that stretch of river, it’s worth taking a few seconds to contemplate the idea that time travel does exist. The idyllic scene described above – or something like it – has been part of the planet’s story for nearly 300 million years. Of all the flying insects in the world today, mayflies are often considered the most primitive, providing us with a link that runs nearly all the way back to the origins of flight.

Nearly.

Because they weren’t the first. We don’t know what was, or when it did it, or how or why it went about it, but at some point, somewhere, somehow, something took to the air and embarked on our planet’s first powered flight.

We do know it was an insect. And we can be fairly sure it was sometime between, say, 400 and 325 million years ago. This isn’t a narrow window, even by the standards of geological time. For that, as with many things, we can blame the fossil record.

The trouble with the fossil record is that there’s simply not enough of it. Imagine watching a film, but the projectionist shows you only a quarter of a second every eight minutes. That is the fossil record.

How convenient it would be, how satisfying, to be able to slot it all together, to dispense with ‘probably’, ‘may have’, ‘some think that’, and all the other weasel words that necessarily accompany any discussion of our world as it was for the millions of years before we turned up. But, on the other hand, then where would we be? We would know everything there is to know about life on Earth, and that would be a different kind of awful. Having all the answers isn’t necessarily all it’s cracked up to be. Curious ignorance can be healthy.

Not everything that lived is preserved. Very far from it. And what we do have is sometimes the scantest trace, offering tantalising clues as to what kind of creature they might represent. And the more fragmentary the clues, the more vigorous the debate about their meaning.

Take, for example, Rhyniognatha hirsti,* a fossil from the Rhynie chert,† near Aberdeen in Scotland. It’s about 402 million years old and consists of parts of a creature that might – just might – be the world’s first flying insect.

The word ‘might’ is doing some heavy lifting here, because what exactly Rhyniognatha was remains a matter of some debate. A layperson looking at photographs of it, an indistinct agglomeration of brown shapes on a yellow background, might be reminded of a Rorschach test. There is certainly nothing even remotely resembling a wing in there. Those shapes are in fact head parts, and when those are all you have to work with, conjecture and deduction are a necessary part of the process. Any advanced skill can seem like magic to the uninitiated, and so it is with fossil identification, where the ability to build a convincing picture of a creature from the tiniest sample is crucial. ‘How do you know?’ we ask, stupefied. The answer is usually, ‘Well, we’ve spent a very long time thinking about it.’

Discovered in 1919, Rhyniognatha was first described a few years later as a springtail-like creature, and so the situation remained until 2004, when American researchers Michael Engel and David Grimaldi looked closely at the mouth parts and concluded that their shape, size and general demeanour were hauntingly similar to those of modern mayflies.1 As technology improves, so does our capacity for analysis. A 2017 study by paleoentomologists Carolin and Joachim T. Haug, using advanced microscope technology, cast doubt on the mayfly interpretation – indeed, the authors suggested that Rhyniognatha might be some kind of centipede.2 An arthropod, then, but not an insect. It remains to be seen whether this is the final word, and the case for both interpretations is hotly argued.

There is equal uncertainty surrounding the fossil fragments of an insect from about 385 million years ago found in New York State. Bits of cuticle, a compound eye. What exactly was it? Something insecty, wingless, silverfish-like. Beyond that, it’s difficult to tell.

The same can’t be said for the remains of Delitzschala bitterfeldensis.*3 This one is the real deal, a creamy white imprint on dark shale, the outline of its wings clearly preserved in the rock. You can see not just their shape but the fine tracery of the veins and irregular little white spots decorating the wing. My imagination wants to turn these spots into glowing orange or iridescent purple – something to bring the animal even more vividly to life.

It’s about 325 million years old, this fossil. Wingspan of a couple of centimetres. The wings look both familiar and advanced – you wouldn’t be surprised to see such a creature today. The order it belonged to, the Palaeodictyoptera,† is extinct. And it’s not fully established how they are related to modern insects. But the shape and vein pattern of the wings – elegantly rounded ellipses held upright – are strongly reminiscent of a mayfly’s. Is it fanciful to close your eyes and imagine yourself sitting in an aquatic environment, watching it flutter weakly among the ferns? Yes, it is. But it’s also irresistible.

The problem is this. We have no idea what led to Delitzschala bitterfeldensis. You might expect there to be clues in the fossil record as to how such an advanced wing came about. But between the silverfishy fragments and Delitzschala we have, to all intents and purposes, nothing. Not just a lack of winged insects, but barely any insects at all.

Welcome to the Hexapoda gap – the period from 385 to 325 million years ago, spanning the end of the Devonian period and the beginning of the Carboniferous.

The Hexapoda gap is like a tunnel. At one end, the mid-Devonian.* At this point Gondwana, the supercontinent dominating the south of the planet, has been around for about 160 million years. Atmospheric levels of oxygen are holding steady at about 15 per cent, after dipping down below 13 in the Silurian. Vascular plants are spreading and beginning to form forests. Arthropods are wriggling and crawling their way across the ground. Life, for so long the preserve of the water, has established itself on land.

We emerge from the tunnel 60 million years later, in the early Carboniferous. Gondwana is in the process of merging with Laurussia to form the even larger supercontinent Pangaea. Oxygen levels have risen to above 20 per cent. The plants that were groping their way towards abundance and diversity at the beginning of the tunnel have gone whoosh, spreading and diversifying like nobody’s business. Flying insects have evolved to the extent that we have Delitzschala bitterfeldensis, and possibly plenty of others both like and unlike it – proof that the next barrier, between land and air, has been breached. But in the tunnel, there’s 60 million years of nothing much. Whatever insect life was active in that time was either not preserved or hasn’t yet been found.

Insects being, in the main, small and delicate, the conditions required for their preservation in the fossil record aren’t encountered that often. The hard grey rock of the Rhynie chert is an outlier. Here volcanic springs brought forth water rich with silica, immersing and petrifying everything in its path. A key factor was that the preservation was almost immediate. As a result, the many plants of the Rhynie chert are preserved in extraordinary detail, and along with them a decent chunk of fungi, lichens, algae, cyanobacteria and arthropods, this last category including the aforementioned Rhyniognatha hirsti.4 What we need is a Rhynie chert from the early Carboniferous, yielding just one insect fossil that might answer questions about the development of the insect wing. It’s not too much to ask, surely?

Lacking such information, we have, as yet, no clues as to whether Delitzschala’s relatively advanced wing was the result of slow and steady evolution throughout the Hexapoda gap or a sudden radiation near the end. What we do know is that it, and others like it, flew, even if exactly how they first did it remains a subject for conjecture.

Evolution being what it is, the sudden appearance of complete, complex wings, where there were no wings before, is not an option. Evolution isn’t interested in what might happen at some unspecified point in the future. It works only with what it has to hand. If an adaptation offers a benefit, that adaptation is favoured. This leads to the old question, so often asked by those dubious about the credentials of evolution by means of natural selection: what use is half a wing?

Plenty, as it happens. The point is that an evolutionary adaptation merely has to be an improvement on what was there before, offering a better chance of survival, however tiny. In the same way that eyes didn’t start as fully developed eyes but merely organs that could distinguish between light and dark, the complex flapping wing started as something much simpler.

But what? And why? And how? Such insects as existed 400 million years ago had barely got used to being out of the water and on the land. What factors might have set the ball rolling on the gradual development of wings?

While many explanations have been proposed, they boil down to two basic ideas.5

The first – the paranotal lobe hypothesis – has little veined lobes sprouting on the front section of the insect’s thorax. These lobes might have had some other function, possibly acting as solar panels to help the animal warm up. The added advantage was that they helped stabilise it as it dropped from the top of a plant to the ground, offering at the very least a softer landing, and possibly the ability to glide a short distance. Those with better stabilisers were more likely to survive, so they evolved to become even better, and gradually turned into something that conferred a more tangible aerodynamic advantage. At this stage this would merely have taken the form of being able to travel a little bit further before hitting the ground – from plummet to glide, however short. As they developed, the gliding distances became gradually longer. From stabilisation to short-distance gliding, and then from there – with the addition of an articulation where wing joined to body – to actual ‘Look at me, Ma!’ flapping flight, all in the relatively short space of a few million years.

Counter to this proposal is the – to this layperson equally plausible – gill hypothesis, which points to the gills on the larvae of things like the modern mayfly. They use them for breathing, but they also resemble tiny wings, and while mayfly nymphs swim using their tails, if someone said to you, ‘Those gills could easily, over time, grow big and strong enough to propel something’, you’d have a hard time denying it. Add to this mix the convenient fact that the gills have veining patterns tantalisingly similar to those on insect wings, and it’s easy to see the appeal of this hypothesis.

Lobes or gills? For those of us naturally inclined towards compromise, a recent proposition is even more attractive: namely that the truth is a hybrid of the two hypotheses. Given that each has wings originating from different parts of the body, this might seem counterintuitive, but the ‘dual origin’ hypothesis – that insects’ wings were the result of a gradual merger between paranotal lobes and gills – is, to lapse briefly into racing parlance, coming up on the rails, full of running.

Whatever its origins, the wing quickly became indispensable. And with good reason. A well-made wing is a clever thing. It collaborates with the air to keep a body off the ground. And it does it (and this is the clever bit) merely by existing. A well-made wing is, you might even say, a wonder of nature.

If you were asked to design a wing from scratch, instinct might guide you towards a workable prototype. Biggish, lightish, flattish. A needle is not a wing. Nor is a brick. A piece of A4 paper, on the other hand, is at least a decent starting point, because it has a large surface area for its weight, and that larger surface area produces more lift. But a piece of paper is weak, so you might want to make it from something stronger, or to bolster it with strategically placed stiffeners. But they add weight, which means you need more lift . . .

And so the long day wears on.

Combining lightness with strength is one of the fundamental conundrums facing all would-be flyers. The solution evolved by insects is to make the wings out of the same stuff that is predominant in their exoskeletons: chitin. This extraordinary material – light, sturdy and waterproof – is perfectly suited to building a wing, as long as it can be made thin enough. But a single sheet – like our piece of A4 but much thinner – is too weak. So the wing is made of two layers, tightly compressed and threaded through with a network of veins. The clever thing about this is that the veins not only strengthen the structure but bring blood (‘haemolymph’, strictly speaking) to the extremities. But with that strength comes added weight – they are heavier than the surrounding chitin – so the proportion of membrane to vein is important. Too few veins, and the wing will be too weak; too many, and it will be too heavy.

Looking at an insect’s wing with the naked eye, it appears flat, but of course veins aren’t two-dimensional, and once you get them under a microscope you enter a world of plains and valleys, minuscule hairs and veining networks of fascinating intricacy. While marvelling at these details, you also see something of their structural strength and can appreciate the possibility that they might be strong enough to propel their owner upwards.

But zoom out and once again they look impossibly fragile, the thinness of the cuticle and the filigree tracework of the veining giving the impression that they’d be vulnerable to the merest puff of wind, liable to fall apart at the merest misplaced touch. With such things insects took to the air.

So, we have a wing. It is aerodynamically efficient, and strong enough to withstand any buffeting or wear and tear it might receive in the insect’s short life. Now you need to find a way to move it. A static wing is OK for gliding, if it’s big enough. But to get off the ground, and then to move actively, you need a form of propulsion. Because our insect wing contains no muscle, propulsion must come from the body. The most straightforward solution is to attach the flight muscles directly to the base of the wing with some sort of simple joint. This enables what on the face of it seems a fairly basic and unsophisticated form of wing manipulation.

That – more or less – is how those first flapping wings evolved. Muscle pulls up; wing moves down. But muscles are capable of just one kind of movement – they shorten. If you want to move something in two directions – down and up, say – you need two sets of muscles. One to move it one way; another to move it the other. This pleasingly simple arrangement worked for Delitzschala bitterfeldensis. And it still works well enough for mayflies, which emerged not long after Delitzschala bitterfeldensis graced the airways. While those very first flying insects are long gone, our modern mayflies, built to a similar plan, give us some idea of what they might have looked like. They have long tails, flight muscles attached directly to the wings and, most importantly, wings that don’t fold along their abdomen. It’s this last attribute that places them in the group Palaeoptera,* a fairly loose gathering of unrelated insects with similar characteristics (what is known as a ‘wastebasket taxon’) in which can also be found the dragonflies.

It’s one thing knowing how something could have happened; still another to understand why. In making its way from water to land, life had already overcome a significant barrier. The modifications required for transition from one environment to another are considerable. A creature adapted for life underwater will struggle on land, and it’s a similar story getting from land to air. Different skill sets are required, different abilities, but mostly a different anatomy. And for all these modifications there needs to be an incentive. Gravity is powerful, and you’d need a good reason to defy it.

Not being eaten is the most immediate incentive. If you can’t outrun danger, a short glide might just do it – and even better if you can flap your way to freedom, casting a backwards glance to enjoy the baleful glare of your disgruntled attacker.

There are also less immediate advantages. If you can fly you can travel further to find your own food, and you can get there faster than your leaden-footed earthbound rivals. Imagine you’re a Devonian insect feeding on spores at the tip of one of the tall plants that seem to be all the rage these days. There’s another plant over there, just too far away for a jump. How much time and energy you’ll save if you can fly to it, without having to go through the tedious business of climbing down the stalk to the bottom, along the ground and then up the next stalk.

Looking to the medium and long term, flight enables you to disperse. Maybe this dispersal is, in the first instance, short range. This is useful in the event of your local habitat being, for example, devastated by fire. Then, over time, the range of dispersal radiates, enabled by the superior ease and speed of travelling in the air versus the slog of land travel. This is a good thing for the growth and diversification of the gene pool.

Having wings has an added benefit, not directly related to flight. If you’re a cold-blooded animal, a quick-warm system is immensely useful, enabling you to get going more quickly in the morning. How useful to have a couple of solar panels strapped to your body. And once they’ve grown to a certain size, you can start to decorate them with bright colours and eye-catching patterns, all the better to attract a mate or warn a predator that you’re poisonous and therefore not suitable snacking material.

Such benefits, accrued in tiny increments, were strong incentive for evolution to favour the development of wings in some species. But there were costs associated with it all. Flying is expensive, energy-wise, and the muscles you need to power yourself into the air are not light. What’s more, once you’ve grown your wings, they present a problem for those times when you’re not using them – great for flying, awkward for hiding in small spaces.

None of the problems associated with flight are insoluble, but the margins are small, and for many animals it’s just not worth the candle. Perhaps they’re too big, too heavy, not fast enough. Perhaps the difficulty of making the change outweighs the benefits it brings. Or perhaps they’re successful enough doing what they’re doing. But for some, flight offered an alternative way of life, and they embraced it. Insects with the ability to fly prospered, passing on their advantageous traits to their offspring, and before long (in geological terms) wings became standard equipment.

The mayfly’s story is a romantic one. The insect that lives for a day. It serves as a useful prompt for us to consider the brevity of our own existence, to remind us to seize the moment, to live life to the full, not to waste time on fripperies. They are the embodiment of the ephemeral, a fact reflected in their scientific name: Ephemeroptera – ‘short-lived wings’.

The only thing is, it’s not entirely true.

We take as our default mayfly, from the approximately 3,000 species worldwide, the one known as the green drake. Ephemera danica, to give its scientific name.

The adult, sure enough, is short-lived – anything from a few hours to a few days. But before they reach that final flourishing, their nymphs have spent up to two years doing the donkey work, sitting on the riverbed, doggedly hoovering up tiny plants and algae, and going through up to twenty stages of growth before emerging to complete the cycle. That we focus on the glamorous adult stage is entirely understandable, but spare a thought for the hard-working nymph.

When the time comes, as it must, up floats the nymph to the water’s surface. Some, resistant to change, expend valuable energy struggling back down to the riverbed, where everything is comfortable and familiar, rather than embracing the inevitable. The ones that save energy, submitting to whatever may happen and allowing themselves to float to the surface, are better equipped to deal with what comes next. Given that what comes next might be a hungry trout, speed is of the essence. Once on the water’s surface, the nymph shucks off its restricting exoskeleton and emerges as a flying insect. Incidentally, this fact alone – so commonplace in the insect world, so abundantly practised, so pivotal to their success – remains a thing, at least to my mind, of extraordinary wonder.

The insect that emerges is an adult rather than a larva, but it is not the full adult of folkloric fame. It’s the intermediate subimago – known to fly fishers as the ‘dun’ – and it is unique. Because in all the astonishing variety and diversity of insect life, mayflies are the only ones with two flying adult stages.6

Not to go on about it or anything, but I’ll just say that again. The only ones. Millions of insect species on the planet, and these 3,000 or so choose a life cycle avoided by all the others.

Why? What advantage does the apparently cumbersome use of a short-lived, clumsily flying intermediate stage confer?

Good question.

Other aquatic larvae – dragonflies, for example – might crawl onto land to make the transition to adulthood. But mayflies (most of them, at least) eschew the land completely. The dun has one job: fly from here – the water’s surface – to there – the river’s edge, where the moult to full adulthood can take place. And do it sharpish, because that hungry trout’s getting closer.

The dun – drab in colour, hence the name – differs from the adult (‘spinner’, in fly-fishing parlance) in one key area. Its wings are covered with microscopic downy hairs called microtrichia.7 It’s thought that they help slough off the water that would disable the adult’s smooth, hairless wings. This is an important adaptation, helping bridge the abrupt transition from life aquatic to life aerial. Its brief time on the water’s surface is fraught enough with peril without worrying about drowning. Despite this, many duns perish at this stage.

The dun is able to fly almost immediately. Its weak, fluttering flight takes it to a waterside perch, where it can undergo the final stage in its remarkable life cycle.

A resting mayfly seems to sit on its belly, the legs providing some lateral stability, the hind segments of the abdomen curving gently into the air. The three spikes of the tail (cerci) stick out like the untameable hairs of an old man’s eyebrows. The eye is drawn to the rounded triangle of the forewings, held stiff and upright away from the body – in some places mayflies are known as ‘upwings’ – and it’s only if you get a chance to look more closely that you might see the less developed hindwings lurking in their lee.

The thing about mayfly wings is that they’re not very good. The other thing about them is that this is absolutely fine. They don’t need to be the best; they just need to do their job. A mayfly has no need to hunt. It has no mouth parts, living instead on energy stored while in the larval stage. It has no need to migrate. Gliding, hovering, soaring and all the other activities potentially available to winged creatures are of no interest to it. All it wants is to get into the air for long enough to find a mate and breed.

The males fly up in a swarm, using their precious reserves in the energy-intensive activity of flight. It’s a stumbling, fluttering flight, their abdomens and cerci hanging down below them in ungainly fashion. Their flapping is slow enough for the wing movements to be visible to the naked eye. But what we can’t see is what happens to the air around the wings.

An insect’s wingbeat is divided into two half-strokes, conveniently labelled ‘downstroke’ and ‘upstroke’. The downstroke is executed more slowly, and at a deep angle, to produce thrust as well as lift; then the wing is flipped over so the leading edge is facing backwards for the shallower, faster upstroke. Repeat multiple times per second.

As well as pushing down on the air to lift the insect up, that angled downstroke also produces what is known as a leading-edge vortex (LEV* for short). The LEV is variously described as ‘tornado-like’, ‘spiralling’ or ‘swirling’. Whichever description you favour, its effect is to increase the speed of the air above the wing. With faster air speed comes lower pressure, and therefore increased lift. Even at the relatively slow wingbeat speeds produced by a mayfly, the combination of these forces is enough to propel them into the air. This is the method favoured by most insects.