As the lid is slowly lifted, I’m not sure what to expect. ‘There it is,’ says the museum curator with a wistful smile. ‘It looks rather sad, doesn’t it?’ I have to agree. I’m looking down at the most famous dodo in the world, but all there is is a desiccated head. It lies on its side in a cardboard box, its one visible eye half closed. Its wizened face, with large protruding beak, is framed by a taut balaclava of black, leathery skin with a few stubby feathers sticking out. Next to it is what looks like the bird’s mirror image, another dodo staring back at the first through a single hollow eyehole. But it is, in fact, part of the same bird. When Victorian scientists scrutinised the dodo, they peeled away the skin from one half of the skull then laid it out like some bizarre death mask. In another, much smaller box there’s an ossified eye socket. In a third, a bony foot and some bits of dried, scaly skin. It looks like a post-pub binge KFC.
These, then, are the remaining body parts of the celebrated Oxford dodo, kept with care and respect at the university’s Museum of Natural History. So unusual is the exhibit, it inspired Oxford University don Charles Dodgson (aka Lewis Carroll) to incorporate the dodo into the children’s classic Alice’s Adventures in Wonderland. But just as the Cheshire Cat disappeared until all that remained was a grin, so too the Oxford dodo, a resplendently full specimen, disintegrated … until all that was left was this. It may ‘only’ be a head and a foot, but with dried skin and flesh, it is the best-preserved dodo in the whole wide world. Other museums may have dodo bones, but there really is nothing quite like this.This is the story of how this remarkable bird made a journey spanning thousands of miles and hundreds of years to arrive in Oxford where its DNA was decoded, and how it inspires, in me at least, the dream of bringing the dodo back to life. I was expecting something gruesome and macabre, but what I find is something sad and beautiful. This bird, desiccated and dissected, ancient and iconic, carries with it an unexpected air of dignity and calm. This is the face of the last dodo on Earth.
As Dead As
As dead goes, it doesn’t get any deader than a dodo. The poster child of extinction, they even get their own idiom. To be as dead as one, the saying goes, is to be unambiguously and unequivocally not alive. The phrase implies there are degrees of dead-ness; that some things are deader than others. If there were a scale of ‘deadness’, dodos would be off it. Dodos are the deadest things there are. So if ever there were a candidate for de-extinction, surely the dodo would have to be it? To be ‘as alive as a dodo’ may not have quite the same ring, but it would certainly make a nice change, not least for the dodo.
The dodo was a large flightless pigeon that once lived on Mauritius, a small island in the Indian Ocean thousands of miles from the East African coast. Yet despite its prominence in our collective consciousness, we actually know very little about it. What we do know comes from the study of its remains – a handful of mummified body parts, thousands of disarticulated bones – and from the reports of those who saw or heard about this remarkable creature. Seventeenth-century sailors who visited the island painted and sketched the bird, and wrote descriptions of it in their journals, but their colourful reports are full of inconsistency and contradiction. According to the various records that exist, the birds were easy to catch, they were difficult to catch. They were slow, they were agile, they were smart and they were dumb. Then, as the sailors returned home and news of the dodo spread, other artists, most of whom had never seen the bird alive, also began to paint it. They used artistic licence to fill in the gaps in their knowledge and satisfy their patrons’ preconceptions. As a result the dodo has been variously portrayed as fat, thin, stooped, straight, bumbling, athletic, pigeon-toed, web-footed, brown, grey, black and blue. Like some paint-fuelled version of Chinese whispers, the birds became less like their true selves and more like the big-bummed bungling caricatures many of us think of today when we imagine the dodo.
With their oddly proportioned bodies and comical looks, they were all too easy to poke fun at. Dutch seafarers dubbed them ‘dodaersen’, or ‘fat-arses’. It’s an insult that may have morphed into the name we know them by today, and that may also have laid the foundations for a major insecurity complex. Was the dodo the first animal to fret about the size of its behind? Did it wander the forests of Mauritius lamenting its puffy plumage and pondering that apocryphal question: ‘Does my bum look big in this?’ Even the great wig-wearing eighteenth-century scientist Carl Linnaeus joined in. According to the dodo’s reputation, Linnaeus bestowed on it the scientific name Didus ineptus. And although the official moniker has since changed,1 the bird’s common name is still used in derogation. Ask most people what they know of the dodo and they’ll tell you they were stupid, fat and sluggish. An evolutionary disaster, they were too dim to sidestep the blows of those who came to kill them and too slow to outpace extinction. The truth is, it’s all a bit unfair. It’s too easy to poke fun at something we know little about, which is no longer here to defend itself or otherwise prove us wrong.
What I can tell you is this. Some time in the last seven million years (no one is really sure when), the dodo’s ancestor – a much smaller, airborne pigeon – landed on Mauritius. The island paradise was a welcome stopover, so much so that the birds decided to stay. With no natural predators and a forest floor littered with fallen fruit, the birds found they did a lot less flying and a lot more walking. Flight, after all, requires a lot of energy, so it’s far easier to not bother if you don’t have to. Then, sculpted by evolution over many generations, their wings began to shrink until eventually they lost the ability to fly altogether. And they got bigger. According to the ‘island rule’, island-dwelling species change in size depending on the resources they encounter. Bigger mammals, delightfully, shrink; there was a time when there were mini mammoths on Cyprus (Mammuthus creticus) and hobbit-sized humans (Homo floresiensis) in Indonesia. Rodents and birds, however, tend to grow bigger. Minorca had its giant dormouse (Hypnomys mahonensis), Madagascar boasted the enormous elephant bird (family Aepyornithidae) and Mauritius witnessed the rise of the dodo.
Although no one knows exactly when the dodo evolved, nor how many there were during the bird’s heyday, we do know that 400 years ago, life was good for the dodo. The giant pigeons lived amidst dense forests of ebony and palm, shooting the breeze with exotic birds and giant tortoises. They scrumped for fallen fruit, built their nests on the ground and raised their young unbothered by any menace.
But a distant speck on the horizon was about to change all that. In September 1598, Dutch ships en route to the East Indies spied the island idyll from afar. The sailors, who had been at sea for months, were exhausted, hungry and out of fresh water. So they weighed anchor offshore and rowed towards the beach. What they found was like manna from heaven – birds so plentiful they could swipe them from the sky with sticks, fish so abundant they were netted with ease and giant tortoises so compliant they could (as one early picture shows) ride them along the beach. And then there was the dodo.
‘They walked upright on their feet as though they were a human being,’ said one record from the time. It had ‘the body of an ostrich’, ‘three or four black quills’ instead of wings and a ‘round rump with two or three curled feathers on it’. ‘Their war weapon was their mouth, with which they could bite fiercely,’ said another report. So when the sailors walked up to them and clubbed them to death, it wasn’t that they couldn’t fight back, it’s that they chose not to. Their problem was not one of weaponry, but of attitude. ‘Modern pigeons are uniformly aggressive across the board,’ says present-day ornithologist and dodo expert Julian Hume from London’s Natural History Museum. ‘Dodos were unlikely to be any different. But these birds had never seen humans before so they didn’t perceive them as a threat.’ Dodos, it seems, were suicidally curious and hopelessly trusting of humans. The cry of a captive dodo would draw others from the forest, which could then be grabbed as well. It’s because of this that people thought them stupid. ‘But they weren’t,’ says Hume, ‘they were just very naïve.’
Faced with an exotic, unique giant of a bird that was like nothing they had ever seen before, the hungry sailors thought of one thing only – what it would taste like. So they killed them and carried them back to the ships’ kitchens. What a disappointment that was. Unlike most exotic animals, the dodo didn’t taste ‘a bit like chicken’; it was, apparently, ‘offensive and of no nourishment’.2 ‘Although we stewed them for a very long time,’ one sailor wrote, ‘they were very tough to eat,’ so the dodo received another nickname: ‘walghvogel’, or ‘repulsive bird’.
For those dodos unlucky enough to be captured and cooked, it was an ignominious death, but for those left alive on the island it was the start of a much slower passing. Ideally situated as a stopover for their fleets as they criss-crossed the Indian Ocean, the Dutch visited Mauritius many times before setting up a permanent base there in the 1630s. Along the way, they wrecked the dodo’s natural habitat, felling forests to make way for sugar plantations, and flooded the island with invasive species. Rats, monkeys, pigs and goats competed with the dodo for resources. They destroyed the dodos’ nests and predated their eggs and chicks. The dodo went into steep decline.
Back to Blighty
Some birds, however, left the island alive. Sailors recognised there was money to be made from unusual-looking creatures if they could sell them to collectors on faraway shores. So the Oxford dodo was bundled into a crate and shipped to Great Britain. Cooped up in a crate for months on end, it must have been a miserable journey, but it’s thought that the Oxford dodo survived and made it to London alive. English theologian Hamon l’Estrange describes an encounter with what is presumed to be the Oxford dodo in 1638. He was walking through the back streets of London when he stumbled across a board outside a house advertising a ‘strange looking fowle’. Inside, up some stairs, he found a stocky, turkey-sized bird kept in a cage. The keeper fed it pebbles – ‘some as big as nutmegs’ – to aid its digestion, and called it a dodo. Here was proof that one dodo at least had made it to Europe alive. But when the bird fell off its perch, as it inevitably did, the gawping didn’t stop.
First it ended up in a pay-to-view collection in South London called the Tradescant Ark, which listed in its catalogue a ‘dodar, from the island Mauritius it is not able to flie being so big.’ But when the owners of the collection died, the dodo passed into the hands of family friend Elias Ashmole, who put it on display in Great Britain’s first public museum, the newly built Ashmolean at Oxford.3
The Oxford dodo was finally in Oxford, but its future was not looking rosy. Back then, museums were fairly hands-on affairs, with visitors encouraged to pick up and manhandle the exhibits. With its oddly shaped proportions and unusual beak, the dodo must have seemed particularly inviting. Little by little, passed from pillar to post, the Oxford dodo began to deteriorate. Insects invaded its poorly preserved body and in 1755, when the museum’s trustees met for a routine inspection of the exhibits, they decided that the Oxford dodo was so ravaged it should be destroyed and replaced with a better dead dodo.
But there was just one problem. There were no more dodos to be had. In Mauritius, the last of the dodos was gone by the end of the 1680s. Extrapolating from this date, present-day experts estimate that the species became ‘as dead as’ sometime around 1693. With all living dodos gone, the Oxford dodo was irreplaceable. What happened next has become conflated into Oxford folklore. Unaware that the dodo had become extinct, museum staff did as they were told and chucked the Oxford dodo onto a bonfire where its body quickly burst into flame. But then, at the eleventh hour, an asbestos-fingered museum assistant decided to defy protocol and pluck what was left of the bird from the flames. A chargrilled head and a single foot were retrieved and returned to the museum, where I visited them more than 250 years later.
It’s a story that infuriates the dodo’s current protector, Collections Manager at Oxford University Museum, Malgosia Nowak-Kemp. The truth, she explains to me on the day I make my own inspection, is far less dramatic. ‘There was no fire,’ she says. The non-bony parts of the bird simply rotted away and were discarded. The conflagration myth emerged from a mistranslation – a Latin word for ‘inspection’ was mistaken for the Latin word meaning ‘purification by fire’. ‘The head and foot were put aside because they were the only parts of the bird worth saving.’
By the nineteenth century, the only known dodo remains were the Oxford head and foot, another foot in London, a skull in Copenhagen and a leg and bit of beak in Prague. So scant were the remains, so distant were the memories, some doubted the dodo had ever existed at all. The alternative, that it had existed then gone extinct, was unthinkable to the vast majority of Bible-believing literalists. Said one author of the time: ‘The dodo … appears to have existed only in the imagination … or the species has been utterly extirpated … which is scarcely possible.’ The Oxford specimen was, he said, an unknown species of bird that was still alive somewhere. For the Oxford dodo, it was a period of unprecedented existential angst. Had it ever existed at all?
Stuck in the Ashmolean with literally no body to turn to, the remains of the Oxford dodo idled the decades quietly. Then in 1847, came the first of two dissections. Victorian scientists teased apart the bird’s head. Their goal, according to Nowak-Kemp, reached beyond intellectual curiosity. In a university then bereft of any science at all, the act served to raise the profile not just of the dodo but also of science itself. The scientists concluded that the dodo was not, as some had thought, some sort of a vulture or albatross, but a pigeon. The dodo was back in the game. People believed in it again.
The university built a new museum to house its scientific collections and to teach and research the sciences. In 1860, the Oxford dodo left the Ashmolean and moved across town to the new, cathedral-like Museum of Natural History, where it can still be found today. The museum is a Gothic masterpiece. If you ever find yourself in Oxford you must go and visit. On a sun-kissed autumn morning, its vaulted glass ceiling bathes the museum with light and warmth, illuminating the remarkable creatures presented there. It was with this in mind that just before the new millennium rolled in, Malgosia Nowak-Kemp quietly removed the Oxford dodo from public display and found it a new resting place, away from the bleaching rays of the sun in a cool, windowless backroom. The dodo that you see on display in the public gallery is a model, the skull next to it, a replica. But ask her nicely, and Nowak-Kemp, known also as ‘the dodo lady’, might show you the real deal. She has been looking after the Oxford dodo for the last 25 years and finally, it seems, the bird is being given the protection it has so desperately needed. The remains rest on tissue paper in specially selected storage boxes, acid free so as to minimise discolouration and decay. From time to time the boxes are moved as a precaution against theft. But when I visit, they are stashed in an elegant cabinet of curiosities amidst an eclectic collection of strange skulls, carapaces and horns. Nowak-Kemp handles the boxes with care and respect, laying them down on a nearby table as gently as a mother would a newborn. When the lid is lifted, we stare at the bird together. ‘Do you ever get tired of looking at it?’ I ask her. ‘Never,’ she replies.
We look but don’t touch. I photograph but don’t flash. With half the skull’s skin removed, the scars of the Victorian dissection are obvious. But those of the second are far less visible. In 2001, the University of Oxford was home to a thriving ancient DNA research laboratory under the leadership of Alan Cooper, now at the University of Adelaide, Australia. For those interested in ancient DNA, it was a time of immense optimism. Researchers had extracted the molecule from Egyptian mummies, mammoths and Neanderthals, and Cooper himself had extracted DNA from another extinct and flightless bird, New Zealand’s giant moa (Dinornis giganteus). ‘In the early days of ancient DNA it was all about who could get their hands on the coolest specimen,’ says ancient DNA researcher Beth Shapiro (now at the University of California, Santa Cruz), who joined Cooper in his lab round about that time, ‘and it didn’t get any cooler than the dodo.’ They wanted to try to retrieve DNA from the Oxford dodo, not so they could resurrect the bird, but so they could use any DNA still left in the bird’s shrivelled remains to help understand where the unusual bird perched on the tree of life.
The duo was granted access to the iconic artefacts. They began by retrieving samples of soft tissue, or ‘crusties’, as Shapiro calls them, by scraping away at the inside of the dodo’s skull. But the samples yielded no DNA. So next they took a drill and bored a tiny hole into the dodo’s leg bone. This time they hit the jackpot. The team was able to retrieve short snippets of mitochondrial DNA, from which they were able to confirm that the dodo was indeed a pigeon, whose closest living relative is the sultry, iridescent Nicobar pigeon (Caloenas nicobarica). Google it – it’s a peach!
That such information could be gleaned from mitochondrial DNA was impressive, but the duo knew their limits. Any nuclear DNA that might exist would be present in such small amounts it would be impossible to detect with the techniques of the time. And with the Oxford dodo a precious one-of-a-kind, removing any further samples for analysis was unthinkable. So here, for now, ends the story of the Oxford dodo. Its remains under the watchful eye of Malgosia Nowak-Kemp, and long may it rest, preserved and peaceful, in the place that has offered it respite for the last century and a half.
But the search for dodo DNA goes on. The vast majority of all dodo bones ever found originate from a single source, an ancient dried-up watering hole located close to the coast of southeastern Mauritius. A little over 4,000 years ago, all sorts of animals, including dodos and giant tortoises, regularly visited the site, but then drought set in and the lake began to dry up. Animals continued to crowd around the dwindling waters, their excrement mixing with the increasingly salty and muddy mire. This, analyses of sediment cores reveal, helped to promote the growth of potentially toxic bacteria. Hundreds of thousands of animals became stuck in the mud and died through intoxication, dehydration and trampling.
Today the area, known as the Mare aux Songes, is a grassy swamp not far from the island’s Sir Seewoosagur Ramgoolam International Airport, and the anaerobic sludge that killed so many animals in the past subsequently helped to preserve their remains. The fossils found at the Mare aux Songes are so common and well-preserved that the area has been designated a lagerstätte (German for ‘storage space’), a term used to designate only the most exceptional of fossil sites. Recent excavations, by Beth Shapiro, Julian Hume, and others, have yielded hundreds of dodo bones. When the hapless birds became stuck in the mud 4,000 years ago, their top halves rotted away, but their mud-encased lower limbs were preserved. Many of the dodo bones found are leg bones.
Using cutting-edge techniques, Shapiro has tried to retrieve DNA from more than 50 different dodo bones pulled from the Mare aux Songes, but, aside from a few short mitochondrial sequences, she’s had little joy. Although the bones are in good condition, the DNA inside their cells is not. A few thousand ‘letters’ or ‘base pairs’ of mitochondrial DNA is one thing, but it’s a far cry from the billion or more base pairs of nuclear DNA that make up the complete genetic code of a bird. The dodo’s nuclear DNA is either so badly degraded that there’s genuinely none left any more, or the little there is is in such bad shape it remains beyond the reach of current methods.
I ask Shapiro if there’s any small glint of hope, any conceivable chance of ever getting DNA from the dodo. She gives it to me straight. ‘It’s unlikely that we’re ever going to find any specimens on Mauritius with DNA in decent shape.’ The island is too warm, which makes DNA disintegrate. And the Mare aux Songes, where 99 per cent of all the dodo remains ever found come from, is too wet and too acidic, which makes DNA disintegrate. ‘It’s everything that you don’t want when you’re trying to preserve DNA.’ The only hope of finding dodo DNA, says Shapiro, would be to find an expat dodo that died abroad and was then kept carefully at a cool, constant temperature over the centuries. It’s not going to happen. We humans have a long history of not looking after the dodo – of killing it, eating it, destroying its habitat and then hanging around doing nothing while its ill-preserved remains fall to bits. If the most complete specimen we have is the Oxford dodo with its wizened head and time-ravaged snippets of mitochondrial DNA, then the bird’s full genetic code is likely to remain forever beyond our reach. Without its genome there is simply no hope of bringing back the dodo. My dream of de-extincting it is ‘as dead as … ’. It’s time to face the truth. I will never have the pet dodo of my dreams.
I’m gutted. Who wouldn’t want to see a dodo for real? I’d dress up as Alice, give it a cane, put it in cufflinks and have it stage a Caucus race. That way, everyone would be a winner.4 As birds go, the dodo was one extraordinary pigeon, the likes of which we’ll simply never see again. But the dream of resurrecting an extinct funky pigeon doesn’t have to end there. There is another extinct pigeon, one that died more recently, that scientists think they can bring back.
An Avian Eclipse
When the dodos were dying out on Mauritius, a much smaller pigeon with wings that still worked was darkening the skies of North America. They weren’t dumpy like the dodo, or sultry like the Nicobar pigeon – these were speedy and svelte. Males were cobalt blue with a peach-coloured breast, bright red eyes, and coral legs and feet. Females were, as females are, a little more subtle. At the start of the nineteenth century, the birds existed in mind-boggling numbers. There were billions of them. Their flocks were so large they literally blotted out the sun – an avian eclipse. Sometimes a flock took days to pass overhead. The collective beating of their wings was like the rumble of thunder and, some said, created a draught so powerful it actually chilled those on the ground below. Where the dodo, hidden away on its rural island idyll, had been easy to overlook, these birds, by their sheer numbers, were impossible to ignore.
The birds were passenger pigeons (Ectopistes migratorius), also known as the ‘Blue Meteor’, once the most abundant bird in North America, and probably the world. At one time there were more passenger pigeons than there were people alive on Earth. It’s almost impossible to imagine, apocryphal even. But try … A single flock could be over 100 miles long and a mile across. If all the birds in that flock had flown single file, beak to tail, the line would have circled the Earth 22 times. If you took all the pigeons in the UK, multiplied them 400 times, then launched them into the air, that would be the size of a single passenger pigeon flock. And then, one day, they were all gone. The passenger pigeon went the way of its Mauritian cousin.
That the passenger pigeon could go from such enormous numbers to nothing in the space of a few decades is devastating, but we have no one to blame but ourselves. In their heyday, these immense flocks roamed the deciduous forests of the eastern and midwestern United States and Canada, gorging themselves on the acorns and beechnuts they found there. Like feathered locusts, they would appear en masse and ransack entire forests. Then, with their food supply exhausted, they’d simply take to the skies and move on. A seemingly inexhaustible supply of free protein that was all too easy to catch, we massacred them in their millions. So dense were their flocks that a single shot could slay dozens of birds at a time. There was no need to aim. A blind man could have pointed his rifle into the air and still brought them down. We clubbed them out of the sky with sticks and we blasted them with cannons. We poisoned them with whisky-drenched corn, set fire to their roosts and asphyxiated them with burning sulphur. We lured them into vast nets via the cries of captive pigeons that we tied to stools with their eyelids sewn shut, giving rise to the term ‘stool pigeon’ and, some time later, a song by Kid Creole and the Coconuts.
In the late 1800s, as the telegraph and railways spread, hunters found that they could hear about and travel to new nest sites all too easily. Passenger pigeons, the cheapest source of protein in the United States, became big business and the pigeon-ocide continued on an industrial scale. Bunged into barrels, the dead birds were sold by the tonne. Boasting a dark meat that was apparently delicious, most ended up baked, stewed or wearing pie-crust lids. Some people thought to stuff their pillows with the birds’ feathers in the superstitious belief it would bring long life. It didn’t. Not to the passenger pigeon anyway. Such was our greed that sometimes barrel-loads of unsold birds were left to rot. What a shameful waste. And if killing them wasn’t enough, we systematically destroyed the forests they relied on for food and shelter. By the 1870s, European settlers had felled half of North America’s native woodland for timber and agricultural purposes. It’s hard to underestimate the effect this would have had on the birds that remained. With their nest sites dwindling, and the acorns and nuts that sustained them in short supply, their numbers began to plummet.
By the time anyone noticed and meaningful legislation was introduced, there were no passenger pigeons left to save. By the early 1900s, the few that remained were confined to US aviaries. Soon only one bird remained, a female called Martha, who lived in the Cincinnati Zoological Gardens, Ohio. Aged and immobile, visitors pelted her with sand to make her move, so keepers had to cordon off her cage. Then on 14 September 1914, Martha, the last passenger pigeon on Earth, succumbed to the inevitable. She died that afternoon and, some said, the United States’ heart was broken. The passenger pigeon became nothing more than a memory.
Realising her significance, zookeepers froze her in a giant ice cube and shipped her to Washington, DC, where she was thawed, skinned, stuffed and put on public display at the Smithsonian Institution. She has since left her resting place only twice, once to appear at a San Diego conference, and once to visit her old haunt, the Cincinnati zoo. Both times, she was flown first class under the private supervision of a dedicated flight attendant. Born, raised and died in captivity, it’s ironic that Martha flew further in death than she ever did in her 27-year-long life.
And that’s the end of the passenger pigeon … except that it might not be. In 2012, a group of ornithologists, geneticists and conservationists, including Beth Shapiro and George Church, got together at Harvard Medical School to discuss whether or not this iconic species could be brought back to life. The meeting was organised by Ryan Phelan and Stewart Brand, who had been thinking about de-extinction and wondering whether it was possible. The experts concluded that it was.
Shapiro had already managed to tease nuclear DNA from the toe pads of museum birds, and gene editing technology was improving all the time. Sure there were technical hurdles, but the mood was optimistic. ‘The meeting was a green light for us,’ says Phelan. The duo went on to set up Revive and Restore, an influential, friendly, non-profit organisation dedicated to advancing the science of de-extinction (and more besides; see Chapter 8). ‘The Great Passenger Pigeon Comeback’ was hatched.
Today, the project is in full swing, at its helm a young scientist by the name of Ben Novak. Funded by Revive and Restore, and working under the guidance of Shapiro in her Santa Cruz laboratory, Novak is doing something that all of us want, but few of us ever manage – living his childhood dream.5 He has been thinking about de-extinction since he was 13 years old. As a kid, he did a science fair project about the possibility of bringing dodos back to life. Then, a few years later, he opened a book and saw a picture of the passenger pigeon. ‘I fell in love with the photo,’ he says. ‘I fell in love with the story.’ He then began to eat pigeon,6 sleep pigeon and breathe pigeon. So desperate was he to get things moving that a few years before he landed his job with Revive and Restore, he raised $4,000 from family and friends so that he could start sequencing passenger pigeon DNA on his own. He has researched their genetics, their history and their ecology, all with, what seemed at the time, a far-fetched dream of bringing them back to life, of giving their sad story a happy ending. So when the Revive and Restore project materialised, he jumped at the chance to get involved. ‘He’s smart. He has a can do attitude, and he has a lifetime of passion behind him,’ says Phelan. He’s also not at all what one would expect of a pigeon fanatic or an academic. Google ‘pigeon fancier’ and you’ll find images of flat-capped pensioners smiling gummily for the camera as they coo over their prize birds. But not Ben Novak. He may have a flat cap but he wears his back to front. He looks like he should be in an indie rock outfit called ‘Ectopistes’ or a UK street dance troupe called ‘Genetic Diversity’. A modest man, he has the nous and technical expertise of a post-doc 10 years his senior. Novak knows more about pigeons than the collective membership of the National Pigeon Association. If anyone can bring the passenger pigeon back, Ben Novak can.
His starting material is the hundreds of skinned, stuffed passenger pigeons that can be found in public museums around the world. Alongside Shapiro, Novak has extracted DNA from more than 80 such birds dating from the late 1800s to as far back as 4,000 years ago. As is to be expected for dead creatures of that age, the genetic material is broken into many, many tiny pieces. So Novak is using Next Generation Sequencing to read the sequences of all of the snippets in a sample in one go. By repeating the process over and over again, he can build up an increasingly accurate picture of the genome, albeit it in millions of tiny pieces. To date, Novak has sequenced 21 trillion base pairs of DNA. That’s a staggeringly big number: it’s ‘21’ followed by 12 zeros.
The next step, then, is to reassemble these fragmented sequences into a full genome, first digitally inside a computer, and then functionally inside a cell. Help is at hand from the passenger pigeon’s closest living relative, a rather average-looking coo-er called the band-tailed pigeon (Patagioenas fasciata), which has a very similar genetic sequence to the passenger pigeon. Just as researchers used the genome of modern humans to help thrash out that of Neanderthals, and the genetic sequence of the elephant has been used to help recreate the sequence of the woolly mammoth, Novak is using the band-tailed pigeon genome as a template against which to match and order the fragments of his passenger pigeon DNA. He now has the full genome from two birds, and bits and pieces of genomes from 37 others.
Next, he will use CRISPR, the gene editing technology being used by Church to mammoth-ify his elephant cells (see Chapter 3), to edit key passenger pigeon genes into band-tailed pigeon cells. Novak will effectively line up the virtual genomes of the passenger and band-tailed pigeons side by side and look for differences between the two. Then comes the tricky bit: working out which of the expected 10 million or so differences are really important. Which sequences, for example, gave the passenger pigeon its broad wings, its muscled chest and its long tail? How about its dappled cobalt wings or its rosy breast? Is there a genetic element to its wanderlust or its preference to flock in the billions? It’s a daunting task.
The trick, says Novak, is to look for genes that have already been linked to certain characteristics, such as plumage and colouring, and then to tease out other, lesser-known genetic sequences that have been positively selected for. These are bits of sequence that have changed so quickly over time that they must have been shaped by something other than random genetic drift. They are stretches of the genetic code so useful that the birds that carried them were more likely to survive, reproduce and pass their genes on to future generations. Perhaps the sequences somehow altered wing shape or visual acuity, making the birds faster fliers or better foragers. Or perhaps they influenced the way their brains were wired, helping them to navigate vast distances. Positively selected sequences leave behind telltale signs in the genetic code that can be spotted by vigilant geneticists. It’s these most salient of sequences that Novak will edit into his band-tailed pigeon cells.
Good! So we have, in theory, a passenger-esque genome inside a living bird cell. The next step is to make a baby bird. ‘Why not do cloning?’ I hear you shout. After all, why wouldn’t you? You have read the previous chapters with intense, page-turning fury. You know about Dolly the sheep, Celia the bucardo and the world’s would-be mammoth cloners. So could cloning be an option?
In mammalian cloning, donor DNA is injected into an egg, which, after a bit of biological jiggery pokery, turns into an embryo, which is then implanted into a surrogate womb. But with birds it’s more complicated. The female’s reproductive system is a bit like an automated assembly line. At one end, the ovary releases a fragile membrane-bound blob that contains the yolk and a tiny spot of DNA. Then, as the blob begins to tumble down the bird’s oviduct, the white and then the shell are added in turn. By the time an egg is laid it is too developed, not to mention too covered in shell, to be of use for cloning, and even if it were, there would be no womb to return it to. Researchers have been trying and failing to clone birds for a decade or more, leading some to speculate that the procedure is simply impossible. ‘The issue with cloning birds isn’t just that it requires technical finesse, it is also a logistically complex process,’ says reproductive biologist Michael Kjelland from Conservation, Genetics and Biotech, LLC.
Kjelland and colleagues have, however, been working on overcoming these hurdles. His idea is to get in early and collect the eggs as soon as they have been ovulated, but before the white and shell have been added. Working with chickens, because they are easy to get hold of, look after and produce lots of eggs, he uses a steady hand and a tablespoon to scoop out the grape-sized blobs. Next he uses a specially developed technique that combines microscopy with a chemical stain to visualise the egg’s DNA. If cloning is ever to work, the egg’s own DNA must be removed so that the donor DNA can be added, but locating it against the opaque background of the yolk has proved problematic. ‘It was quite a stumbling block,’ he says. With the yolky blob wedged inside a glass beaker, he then punctures the structure and uses a fine glass pipette to remove the DNA. ‘The worry was that the yolk might spill out when we punctured it,’ he says, ‘but it didn’t.’
The next step would be to add the DNA from some would-be cloned bird into the ‘empty’ egg and then coax the reconfigured cell to start dividing. But the developing egg would then need to be physically placed somewhere to be incubated. Here, Kjelland explains, there are two options. One is to transplant the embryo back into the reproductive tract of an adult bird, from whence it could tumble down the oviduct just like any other egg and have its white and shell added. The other is to carefully slice the top off a similarly sized regular egg, tip out its contents then gently place the cloned embryo inside with a little egg white before sealing it up again. No one as yet has tried this last stage with a cloned avian embryo, but Kjelland has sliced the top off a turkey egg and had a regular Rhode Island Red chick hatch from it; proof in principle that the embryo transfer technique will work.
The component parts of the avian cloning process, it seems, are pretty much there, but they need to be refined and practised by skilled, technical hands, then put together. No one has, as yet, done all of the steps from start to finish. ‘The main problem now,’ says Kjelland, ‘seems to be a lack of funding and a defeatist attitude. We need to overcome that.’ But in the meantime, there may be another method, more developed and well rehearsed, that could be used to make a baby passenger pigeon …
Don’t Cry, Daddy
Poor old dads. When a baby is born, its father seldom receives much in the way of recognition. All eyes are on the little one, wrinkled and vulnerable, and on the mother, stoic and resilient, justly exhausted after the Herculean tasks of being pregnant and giving birth. Poor, neglected, unnoticed fathers. No one acknowledges how well they get on with their daily lives as their partner’s belly balloons and her ankles swell. No one congratulates them for eating and peeing normally, while their partner wretches over the sight of toast and struggles with a bladder the size of a pea. Few pat their backs as they stand around the labour suite immersing themselves selflessly in the role of ‘spare part’ while their partner painfully attempts to push a ‘square peg’ through a ‘round hole’. Poor old dads.
New life is created every minute of every day, yet dads rack up little in the way of credit. Then, every once in a while, comes a story that celebrates the role played by the father, a tale that embraces his very unique role in the miracle of creation. This is one of those stories.
In March 2013, a very feathery father bagged news column inches around the world. This was one dad who really had done something quite extraordinary. ‘Duck fathers chicken’ shouted one headline. ‘Chicken has a duck for a father’ yelled another. ‘Chick dad is quackers’ mumbled another apologetically under its breath.7 If ever there was a case for a paternity test, this was it. In some bizarre, laboratory-fuelled feathery tryst, a male duck and a female chicken somehow got it together and managed to produce, not a dicken or a chuck, but a pure-bred baby chick. The new arrival was announced in the peer-reviewed journal Biology of Reproduction, which published a heart-warming photograph of mother hen and daddy drake looking mighty pleased with themselves as they flanked their fluffy, yellow chick against a sunshine-dappled lawn. But this was no ordinary dad. This was a duck with a secret. A secret so secret, not even he knew about. A secret that he kept … in his gonads.
A year or so earlier, when the duck, known un-affectionately as ‘wd25’, was but a tiny embryo he underwent a procedure in a Dubai laboratory. Cell biologist Il-Kuk Chang and colleagues from the Central Veterinary Research Laboratory injected chicken cells into his bloodstream. But these were no ordinary cells. They were primordial germ cells or PGCs, specialised cells formed early in development that do just one thing – sit in the gonads and make sex cells. In the female they make eggs, and in the male they make sperm. When Chang injected the chicken PGCs into wd25’s aorta, they travelled through his blood supply to his gonads, where they bedded down among the duck’s own PGCs and started to make sperm – chicken sperm. With a mix of duck and chicken PGCs, when the drake reached sexual maturity, he started to make both duck and chicken sperm. According to the research paper, ‘semen samples were collected’8 and then used to inseminate female chickens, who then went on to do what chickens do best: lay lots of eggs. Of these, a handful hatched into bona fide chicken chicks – healthy, baby birds that were genetically all chicken, but with a duck father and a chicken mother. Talk about giving a youngster an identity crisis.
It’s an eye-catching piece of science, but one with a much deeper purpose. If the eggs and sperm of one species can be grown inside the reproductive system of another, then the technique could be used to help boost the numbers of endangered species and potentially bring back extinct ones. PGCs from band-tailed pigeons, edited to contain passenger pigeon DNA, could be injected into a host bird embryo. This, most likely, would be a band-tailed pigeon, which would then be allowed to grow up as normal and which would, in time, begin producing passenger pigeon sperm. If female band-tailed pigeons could be similarly altered to produce passenger pigeon eggs, then in theory at least, passenger pigeons could be bred.
Surrogate parents, most likely band-tailed pigeons, could be used to incubate the eggs and look after the hatchlings. But given that band-tailed pigeons are almost monochrome, and that passenger pigeons were multi-coloured, Ben Novak tells me that the surrogates might well have their feathers dyed to make them more convincing. ‘After all,’ he says, ‘there’s no such thing as getting it too right.’ But a baby passenger pigeon might not be expecting much in the way of parental care. Historical records reveal how all the members of a single flock would nest in the same forest at the same time, constructing millions of rickety nests high up in the tree tops. After that, they’d all lay their eggs – one or two per nest, pretty much in unison – then incubate them for a couple of weeks. When the squabs hatched, the parents would feed them ‘pigeon milk’, a fatty, protein-rich paste they produced in their crops, along with bits of regurgitated food. Then, at the tender age of just two weeks old, something incredible happened. The parents gave their babies one last feed, then rose up together and disappeared. They just flew the coop. The helpless baby birds were left all alone, three metres (10ft) up, without food and with stumpy feathers that had yet to morph into wings. Bemused, the increasingly ravenous babies would stay in the nest for a day or two then, one by one, flop down to the forest floor in search of food. It’s like tipping a toddler out of a pram and hoping it can blend its own baby mush. In the few days it would then take for their wings to develop, the grounded youngsters were easy pickings for woodland carnivores. Wolves, foxes, hawks and other predators had a field day. It’s like tipping a toddler out of a pram and hoping it can blend its own baby mush … in a kitchen full of baby-eating tigers. Someone call Avian Social Services.
It seems like a cruel and wasteful strategy, but the likelihood is, with their food reserves dwindling, the adults simply had to move on in search of sustenance. Sure, their desertion led to the deaths of many thousands of chicks, but in evolutionary terms the damage was collateral. The colony as a whole survived to see another day. And odd though it may seem, this lacklustre style of parenting could work in our favour today. Because infant passenger pigeons were simply used to ‘getting on with it’, a newly de-extincted bird may be unlikely to ask much of their surrogate parents beyond a little crop-milk and some regurgitated seeds.
The plan would be to raise the birds carefully in captivity, in as large an aviary as possible, until they reached flock-sized numbers and could be released into the wild. The deciduous forests of eastern North America, once felled by European farmers, have largely regrown, so there’s habitat to be had – although, some argue, maybe not enough. As nomadic birds that followed their beaks to find food rather than retracing defined migratory routes, they shouldn’t need to be taught where to go. Instead, if they’re anything like their forebears, they’ll instinctively flock together and forage, searching out nut-rich woodland and perhaps even, seed-rich farmland. ‘The juveniles will likely form their own social structure,’ says Novak. In terms of numbers, Revive and Restore are aiming for an as yet unknown quantity, but one likely to be in the hundreds of thousands, perhaps the millions. It might sound like a lot, but many birds exist in these kinds of numbers and above. In 2014, there were an estimated 275 million mourning doves. So there’s plenty of room for the passenger pigeon. The key for Novak, and indeed for Revive and Restore, is to recreate a bird that fulfils the same ecological niche as its forebears.
In the passenger pigeon’s case the aim is to make a twenty-first-century bird that behaves like a passenger pigeon and interacts with its environment in the same kind of way. If Novak does his job right, the revived and restored passenger pigeon will roam in dense flocks,9 eating nuts and seeds, destroying some, dispersing others and helping to enhance woodland diversity. It will be a source of protein for carnivores and a source of competition for other fruit and grain-eaters. However, all this will take time. With a lot of basic science still to do, Revive and Restore doesn’t expect to hear the tiny pitter-patter of passenger pigeon feet before 2022, and envisage the first test flocks could be flying by 2032. So, not imminent, but keep watching the skies.
The project is not without its sceptics. Some, such as Beth Shapiro, cite technical hurdles. ‘We can’t de-extinct the passenger pigeon at the moment,’ she says, ‘for lots of reasons.’ No one, as yet, has made or modified pigeon PGCs, much less transferred them into a host bird to have it make sperm or egg, and then used those sex cells to generate live birds. But I’ve worked as a cell biologist. I’ve tinkered with genetic modification. I’ve spent long, frustrating days trying to fathom the exact nutrients needed to keep my petri dishes of cultured cells alive. I’ve curled my fists in frustration as my primitive attempts to genetically edit said cells yielded unspectacular, unsatisfactory results. I know how difficult it can be to work with cells and with DNA, but with the benefit of 20 years’ hindsight, I can see just how far and fast the technology is progressing. Yes, there are hurdles, but with enthusiastic, clever people like Ben Novak at the coal face, there’s no reason these hurdles won’t be overcome.
But just because we can do something, doesn’t automatically mean we should. Ornithologist Mark Avery, author of A Message from Martha, is concerned about the birds’ welfare should we bring them back. In the early days of their de-extinction there would, unavoidably, be small numbers of birds raised and bred in captivity. ‘But we know that these were highly social birds,’ he says, ‘so it all feels rather sad.’ These were birds that flocked in the millions. They needed to. It offered them safety in numbers and buffered the population when so many of their unattended young fell to Earth and got eaten. We can’t bring back and release a handful of passenger pigeons. They wouldn’t stand a chance. With the passenger pigeon it’s all or nothing. We either bring back a flock so large it would darken the sky, or we don’t bother at all. And it’s here that I find myself erring on the side of caution.
In 1855, one witness to a passenger pigeon flock described how ‘children screamed and ran for home. Women gathered their long skirts and hurried for the shelter of stores. Horses bolted. A few people mumbled frightened words about the approach of the millennium, and several dropped on their knees and prayed.’ These were rowdy, riotous birds that left devastation in their wake. They could devour the contents of a newly planted field in minutes. They ruined entire harvests and pissed off farmers on a monumental scale. When they flew down to roost, they’d perch on any and every available branch. If there wasn’t any space, they’d pile on top of one another, causing boughs to break, crushing any birds on the branches below. When they deposited their droppings it was like giant snowflakes falling from the sky, leaving the ground covered in a layer of deep guano. And when they moved on, they left behind a landscape so apocalyptic it was worse even than the aftermath of a toddler’s birthday party. The great naturalist James Audubon said it was ‘as if the forest had been swept by a tornado.’ Opportunistic omnivores, they flew from place to place like feathered locusts devouring whatever they could. And if they ate one thing then found another they liked better, they’d throw up the contents of their crops and keep on bingeing. Passenger pigeons were the hell-raising, feathery bulimics of North America.
To choose as a de-extinction candidate a species whose survival very probably depends on it existing in such vast numbers is, I think, a controversial choice. Perhaps we’d end up having to cull the creatures we went to so much trouble to create. ‘It could be like Martha all over again,’ says Avery. Given that pigeons aren’t exactly the most popular birds alive on the planet today, how ready are we, I wonder, for the passenger pigeon?
NOTES
1 It’s Raphus cucullatus nowadays, since you ask.
2 So more like a doner kebab.
3 In its early days, the Ashmolean met with mixed reviews. With its seemingly random mish-mosh of trivia, critics called it the ‘Knickknackatory’, which did not go down well with Ashmole. Apparently it was all too much and he ‘relapsed into the Gout’.
4 This is a joke for hardcore Lewis Carroll fans. Are there any? Thought not. At the risk of over-explaining a joke and sucking the joy from it … in Alice’s Adventures in Wonderland the dodo organises a Caucus race in which participants can run in whatever pattern they like, starting and finishing at points of their own choosing, so everyone wins.
5 My childhood dream was to open a hairdressing salon for long-haired guinea pigs. Sadly it never became a career option.
6 Not literally.
7 It didn’t but it should have done. The sub-editors missed a trick.
8 The mind boggles … I like to think there was mood music and a copy of ‘Mallards’ Wives’ involved.
9 I’ve presumed, throughout this chapter, that a ‘flock’ would be the correct collective noun for passenger pigeons, but perhaps they deserve their own term. I suggest either a ‘tempest’, an ‘eclipse’ or a ‘Novak’ of passenger pigeons.