Prabir was hoping that they’d find a previously undetected passage through the reef, but as they inched their way around the island watching the sonar display, the chance of that diminished, then vanished altogether. The old southern approach was narrow, and twenty years before no one would have attempted to pass through it in such a large craft, but the autopilot confidently declared that there was sufficient clearance.
They dropped anchor just inside the reef. It was too late to go ashore, with less than an hour of light remaining. The beach appeared smaller than Prabir remembered it, though whether the jungle had encroached, a storm had gouged sand away, or he was just misjudging the tide it was impossible to say. There were still coconut palms standing at the edge of the sand, but he could see the strange thorned shrubs choking out everything else in the undergrowth. There was no sign at all of the path that had once led from the beach to the kampung.
After they’d eaten, Grant made her nightly call home. Prabir sat out on deck, stupefied by the heat. He couldn’t call Felix; he didn’t want to be forced to justify what he’d done to Madhusree, let alone risk some kind of mediated confrontation if the two of them had been in contact.
He lay down and tried to sleep.
Just after midnight, he heard Grant come out on deck. She stood beside him. ‘Prabir? Are you still awake?’
As he rolled over, he saw her gazing down at him with the kind of unguarded fascination that he’d learnt never to betray on his own face by the time he was about fifteen. But then her eyes shifted to a neutral point behind his shoulder, and he doubted the significance of whatever he’d seen.
‘I just thought you ought to know that your extortion has borne its first fruit.’ She handed him her notepad. He glanced at the banner at the top of the page, then sat up cross-legged on his sleeping bag and read through the whole thing.
A molecular modelling team in São Paulo had examined the sequence data from the two expeditions, and identified a novel gene common to all the altered organisms; they’d sent Grant a copy of their results, as well as submitting them to a refereed netzine. Preliminary models of the protein the gene encoded suggested that it would bind to DNA.
Prabir said, ‘You think this is it? Your mythical gene-repair-and-resurrection machine?’
‘Maybe.’ Grant seemed pleased, but she was a long way from claiming victory. ‘Part of what they’ve found makes sense: this gene has a promoter that causes it to be switched on in meiosis — germ cell formation — which explains why there’s no need for a mutagen to activate it in these organisms. But there’s no evidence of a similar gene in any of the original genomes, let alone one that would only be switched on when it was needed to repair mutations.’
Prabir thought it over. ‘Could we be seeing the gene that the original version resurrected in place of itself? Once it went hyperactive, it not only substituted old versions of other genes, it substituted a completely unrecognisable version of itself?’
Grant laughed, through gritted teeth. ‘That’s possible, and it would make things very tricky. These modelling people might be able to determine the current protein’s function, but I wouldn’t count on them to be able to work backwards and determine the structure of an unknown protein that changed its own sequence into the current one. What we really need is DNA from two consecutive generations of the same organism, for comparison.’ She hesitated. ‘And if possible, DNA from two early consecutive generations of the butterflies.’
Prabir said, ‘You mean samples my parents took? They didn’t have your magic gelling agent. And I think the refrigeration would have failed by now.’
Grant looked uncomfortable, unsure whether to pursue the matter.
‘It’s OK,’ he said. ‘I don’t mind talking about this.’ They’d come here for the butterflies; he couldn’t afford to clam up every time the subject was raised.
She said, ‘They might have preserved whole specimens for storage under tropical conditions; there were treatments available twenty years ago that would have protected against bacteria and mould, without damaging the DNA. You said they bred the butterflies in captivity. One or two well-documented samples could tell us a lot.’
‘I appreciate that. But don’t get your hopes up. With all the vegetation changed and the old paths gone, I’m not even sure that I could find my way back to the kampung. And if I can, who knows what state the buildings would be in?’
Grant nodded. ‘Yeah. It was just a thought. We’ll go ashore tomorrow, and we’ll find what we find.’ She stood up. ‘And we’d both better get some sleep now.’
Prabir woke badly, to another Tanimbar dawn. When he opened his eyes there was a message in the sunlight: His parents were dead. Everyone alive would follow them. The world he’d once seen as safe and solid — a vast, intricately beautiful maze that he could explore from end to end, without risk, without punishment — had proved itself to be a sheer cliff face, to which he’d cling for a moment before falling.
He rose from the deck and stood by the guard rail, shielding his eyes. He was tired of the pendulum swings, tired of finding that all the carefully reasoned arguments and deliberate optimism that shored him up well enough, on the good days, could still count for nothing when he needed it the most.
But this could be the last cycle, the downswing deep enough to carry him through to the other side. Wasn’t this the day he’d step ashore and demonstrate once and for all that Teranesia was powerless to harm him, like an IRA debunker striding triumphantly across a bed of hot coals? He might yet return to Toronto at peace, as infuriatingly tranquil as Felix, free of his parents, free of Madhusree, every useless fear banished, every obligation to his past, real or imagined, finally discharged.
And he’d told Grant not to set her hopes too high.
They brought the boat closer to shore, then waded on to the beach. Grant was carrying a rifle now, as well as the tranquilliser gun. They went through the rituals of the insect repellent and the mine detector tests. As Prabir sat pulling his boots on, looking back at the reef, he pictured a water man rising from the waves, angry and ravenous, teeth shining like glassy steel. Then he punctured the illusion, scattering the figure into random spray. That was the trouble with the demons dreamed up by children and religions: you made the rules, and they obeyed them. It wasn’t much of a rehearsal for life. Once you started believing that any real danger in the world worked that way, you were lost.
They penetrated the jungle slowly; the thorned shrubs were even denser and more tangled than the species they’d seen before, with long, narrow involuted branches like coils of barbed wire. Prabir cut off a sample, tearing his thumb on a barely visible down of tiny hooks that coated the vines between the large thorns. He sucked the ragged wound. ‘Nice as it would be to solve the mystery, I’m beginning to hope we don’t stumble across a herbivore that needs this much discouragement.’
‘It’d probably be no worse than a rhinoceros or a hippo,’ Grant suggested. ‘But apparently it has no descendants here, to give birth to something similar.’
Prabir fished in his backpack for a band aid. ‘OK, I can accept that: seeds get blown about, continents drift, animal lineages die out locally. But why is it always the most extreme trait that gets resurrected? Why couldn’t these shrubs just grow something mildly inappropriate, like flowers optimised for a long-vanished pollinating insect?’
Grant mused, ‘There’s no evidence of the São Paulo protein ever having been used for mutation repair. So maybe that was never the case; maybe I’ve been clinging to that idea too stubbornly. It could be that the protein’s role has always been to reactivate old traits, to bring old inventions back into the gene pool from a dormant state.’
Prabir considered this. ‘A bit like a natural version of those conservation programmes where they cross endangered animals with frozen sperm from twenty years ago, to reinvigorate the species when the population becomes too inbred?’
‘Yeah. And sometimes they use a closely related species, not the thing itself. If this protein manages a kind of “frozen gene bank”, it would be even less purist about it: it wouldn’t have any qualms about creating a hybrid with a distant ancestor.’
To Prabir this sounded both simpler and far more radical than the mutation repair hypothesis: shifting the mechanism from an esoteric emergency response to a major factor in genetic change. Most of the same problems remained, though.
He said, ‘That still doesn’t explain how particular traits get frozen and thawed. Are you saying that this plant’s ancestors knew that they’d evolved a spectacularly effective set of defences, and deliberately tucked away a copy of the genes for the next aeon when they’d come in handy?’
Grant smiled, refusing to be provoked. ‘More likely it’s just a matter of the genes that persist the longest having the greatest chance of being duplicated at some point, which then increases their chance of surviving in an inactive form.’
‘And the mimicry? The symbiosis? How does something like that get synchronised?’
‘That, I don’t know.’
They pressed on. Prabir kept waiting for a flash of recognition, for the sight of an old gnarled tree or an outcrop of rock to awaken memories more strongly than the beach. He’d explored this side of the island completely; every step he was taking here was one he must have taken before. But too much had changed. Though the trees themselves appeared unaltered, there were no ferns, there were no small flowers on the ground, just the carnivorous orchids they’d seen on the other islands, and the ubiquitous barbed-wire shrubs. Even the scent of the forest was alien to him. It was like returning to a city to find it repaved and repainted, emptied of its old inhabitants and repopulated by strangers with new customs and new cooking smells. Ambon with its nouveau-colonial refurbishment had seemed more familiar than this.
The black cockatoos were here, too. Prabir stood and watched one for half an hour, waiting for Grant to finish dissecting an orchid.
The bird was sitting in a kanari tree. Using its teeth, it chewed straight through a slender branch that sprouted twigs bearing half a dozen white blossoms swollen with fruit. The cluster of twigs and fruit fell at the bird’s feet, landing on the large, solid branch where it was perched. It proceeded to attack one of the fruits, chewing through the leathery hull, which had not quite ripened to the point where it would split open and spill the seeds, the almonds, on to the ground.
Grant came over to see what he was looking at. Prabir described what he’d observed so far. The bird had extracted one of the almonds from the fruit, and was performing an even more elaborate routine to penetrate the hard shell.
She said, ‘This part’s old hat: its a famous case of specialisation for a food source.’ The bird had broken away part of the shell, and was now holding the nut with one foot while it used the sharp, hooked part of its upper beak to tear out fragments of the kernel; a tongue like a long-handled pink-and-black rubber stamp darted out to pick up the pieces and take them into the bird’s mouth. ‘Going for the unripe fruit is new, though.’
‘So it doesn’t have to wait for the nuts to fall. Which means the teeth are there to help it stay off the ground?’
‘I suppose so,’ Grant conceded. ‘But there might have been any number of reasons in the past why that was a good idea. It doesn’t require co-evolution with the ants.’
Prabir turned to her. ‘If you’d come to this island knowing nothing about its history, nothing about the ordinary fauna of the region — if you’d dropped in out of the sky in a state of complete ignorance about this entire hemisphere — what would you think was going on here?’
‘That’s a stupid question.’
‘Humour me.’
‘Why? What point is there in ignoring the facts?’
Prabir shook his head earnestly. ‘I’m not asking you to do that. I just want you to look at this afresh. If you’d just arrived from the insular British Isles with an immaculate, theoretical training in evolutionary biology, but no contact for a thousand years with anyone east of Calais, what would you conclude about the plants and animals here?’
Grant folded her arms.
Prabir said, ‘I’m withdrawing my labour until you answer me. Forgetting all the history you know, what does this really look like to you?’
She replied irritably, ‘It looks to me as if the affected species originally shared territory with all the others, then became isolated on some remote island and co-evolved separately for a few million years — and now they’re being progressively reintroduced. OK? That’s what it looks like. But on what island is this meant to have happened?’ She spread her arms. ‘It didn’t happen here: you can vouch for that yourself. There’s no island in the whole archipelago sufficiently isolated, and sufficiently unexplored.’
‘Probably not.’
‘Certainly not.’
Prabir laughed. ‘OK. There’s no such island! All I’m saying is, when the account you’ve just given sounds so much simpler than a hundred separate genes in a hundred separate species marching back from the past in perfect lock-step — I have a lot of trouble seeing how it can’t be telling us something about the truth.’
Grant’s expression softened, her curiosity getting the better of her defensiveness. ‘Such as what?’
‘That, I don’t know.’
Prabir had rewritten the image-processing software to run directly on Grant’s camera. In the afternoon, she found the camouflaged fruit pigeons all around them.
Fluttering across the viewfinder between the pigeons were the butterflies. The wing patterns had changed dramatically — the dappled imitation of foliage and shadows they’d acquired was far less striking, far less symmetric, and far more variable from insect to insect than the old concentric bands of green and black — but when Grant finally captured one and Prabir saw the body, he knew they were the descendants of the insect he’d first seen pinned to a board in his father’s office at the university.
The tranquilliser darts were useless for insects, but Grant had a spray based on wasp venom that could temporarily paralyse the butterflies without killing them. Using a net to keep their victims from falling to the ants, they managed to collect half a dozen live specimens of both the pigeons and the butterflies.
Back on the boat, Grant killed and dissected one of the male pigeons, removing the testes and then working under a microscope to extract stem cells and various stages of maturing spermatocytes. She was hoping to catch the São Paulo protein in the act, though given the uniformity of the pigeons it seemed unlikely that it was still producing radical changes in their genome.
Prabir left her to it and stood out on the deck, staring back into the harmless shadows of the jungle, numb with relief as he realised how painlessly the day had passed. Between the distracting riddle of the altered species and the sheer physical effort of gathering samples, he’d had little time or reason to dwell on the significance of the place. And that was how it should be. He’d already mourned his parents, in the camp, in Toronto, and he’d recounted their triumphs a thousand times for Madhusree. There was nothing to be done here, nothing to be remembered, nothing to be learnt but the secret of the butterflies. He refused to imagine them trapped on the island. In the only sense that they survived at all, they’d left in the very same boat as he had.
And though Teranesia had proved to be no more dangerous than the other islands, he was still glad that he’d kept Madhusree away. She might resent his intervention for years to come. She might accuse him of standing between her and the memory of her parents. But the alien jungle would have meant even less to her than it did to him, and he’d spared her the pointless anguish of digging through the ruins of the kampung. His mother had told him, ‘Take her away! She mustn’t see!’ He’d completed what he’d begun when they’d set out on the boat. It had been a long trip, but now it was over.
Grant emerged from the cabin frowning, carrying her notepad.
‘More news from São Paulo,’ she said. ‘They’ve refined their model.’
‘And?’
She propped the notepad on the guard rail in front of Prabir; it was displaying a graphic of a couple of large molecules bound to strands of DNA. ‘I don’t know what to make of this. I was hoping they’d find evidence that some part of the protein resembled a transcription factor, and recognised disabled promoters—’
Prabir stopped her. ‘I used to know all these terms when I was a kid, but I’m pretty hazy now. Can you—?’
Grant nodded apologetically. ‘Promoters are sequences of DNA that sit next to the coding region of a gene, which is the part that actually describes the protein. Transcription factors bind to promoters to initiate the copying of the gene into RNA, which is then used to make the protein: to “express the gene”.
‘If a gene is accidentally duplicated, mutations that build up in the promoter of one copy might eventually stop that copy from being expressed. To identify a gene that’s become inactive like that, you’d need something that was capable of binding to a damaged promoter — something roughly the same shape as a transcription factor, but a little less fussy. And then to reactivate the gene, there’d be a number of possible strategies, either working base by base to repair point mutations in the promoter, or snipping the whole thing out and splicing in an intact version.’
Prabir said, ‘OK, that all makes sense. Now what have the modellers found?’
Grant hit a button on the notepad and animated the graphic. ‘This bloody thing just crawls along causing havoc during DNA replication. What normally happens is: the double helix unwinds, the two strands separate, and DNA polymerase comes along and stitches together a new complementary strand for each of them, from free-floating bases. What the São Paulo protein does is slide along each single strand, cutting it up into individual bases, while splicing together a whole new strand of DNA to take its place. Then DNA polymerase comes along and duplicates that.’
Prabir took the notepad from her and slowed down the animation so he could follow the steps. ‘But what’s the relationship between the old sequence and the new sequence?’
‘Basically, the new one is the old one, plus noise. SPP changes shape as it binds to each base of the original strand — it assumes a different conformation depending on whether it’s cutting out adenine, guanine, cytosine, or thymine — and that in turn determines the base it adds to the new strand. But the correlation isn’t perfect; there are some random errors introduced.’
Prabir laughed, disbelieving. ‘So it’s just an elaborate, self-inflicted mutagen? These creatures might as well be bathing their gonads in radiation or pesticide?’
Grant replied dejectedly, ‘That’s what they’re claiming.’
He replayed the animation. ‘No. This is crazy. If you wanted to add a few extra random errors to your offspring’s DNA, would you take the easy way out and just alter your DNA polymerase slightly, so it made occasional mistakes — or would you invent a whole new system like this for making deliberately flawed single-strand copies?’
‘Well, exactly,’ Grant said. ‘And even if you had a good reason to take that approach, the whole protein’s vastly over-engineered. There are commercial enzymes that do something similar, and they’re about one-hundredth the molecular weight.’
‘Maybe there’s a bug in their software. Or maybe there’s some logic to the changes, some pattern that they simply haven’t noticed.’
Grant shrugged morosely. ‘They’ve synthesised some of the protein for real now; they’re doing test-tube experiments as we speak, to try to confirm all this.’
She seemed to be taking it all too much to heart. Prabir said, ‘You know that the things we’ve seen here can’t be explained by random mutations. Maybe there’s still some way this can be compatible with your theory. But whatever’s going on, at least we’re closing in on it.’
‘That’s true.’ She smiled. ‘They have synthesised protein in São Paulo, and I have cultured fruit pigeon spermatocytes. By morning they’ll know what happens in a test tube, and we’ll know what happens in a living cell.’
When Prabir woke, this prediction had been fulfilled. Grant had been up since three o’clock trying to make sense of the results.
The experiments in São Paulo had confirmed the computer model: fed a few hundred different test strands of DNA, the protein had chopped them up and synthesised new strands of exactly the same length, copying the original sequence but introducing random errors. Another group, in Lausanne, had repeated the work and found the same thing.
Grant had detected RNA transcripts for the São Paulo protein in the pigeon spermatocytes, which implied that the protein itself was being made in the cells; she had no direct test for it. But when she compared sequence data for cells before and after meiosis, the error rate was about a thousand times less than for the two experiments in vitro.
She said, ‘There has to be a second protein, some kind of helper molecule that modifies the whole process.’
‘So they need to look harder at the sequence data?’ Prabir suggested. ‘The gene for it must be in there somewhere.’
‘They’re looking. SPP alone is a bit like a pantograph with a whole lot of superfluous hinges. So maybe this is something that binds to it and stabilises it — not enough to produce perfect copies, but enough to allow its internal state to reflect the last few dozen bases to which it was bound.’
Prabir opened his mouth to say, Turing machine, but he stopped himself. Most processes in molecular biology had analogies in computing, but it was rarely helpful to push them too far. ‘So it could recognise a sequence of something like a promoter, even though it only binds to one base at a time?’
‘Maybe,’ Grant agreed cautiously. ‘They’ve also got hold of samples from the Ambon fruit pigeon, and they’re going to see what pure, synthetic SPP does to an entire chromosome, in the presence of nothing but a supply of individual bases.’
As they waded ashore, Prabir looked down into the warm, clear water where he’d swum with Madhusree, then across the dazzling white beach where they’d played. He wasn’t just cheating her out of a role in the study of the butterflies, he was depriving her of the chance to demystify the island, to purge it of its horrors the way he was doing for himself.
But he could never have brought her back here. He could never have undone the one good thing.
Grant wanted to collect specimens of the butterfly’s other stages, so they spent the morning doing nothing but searching appropriately succulent leaves for the spiked larvae, and the branches of the same trees for pupae. The original versions would not have been hard to spot: both had been covered in bright-orange patches, warning colours to signal their toxicity. Grant found signs of leaf damage that looked promising, but there were no culprits nearby. If the larvae had switched strategy and opted for camouflage that was as efficient as the adults’, their movements would be far too subtle for the image-processing software to detect.
They stopped and ate lunch in the middle of the forest, in a rare spot where the ground was rocky enough to keep the shrubs at bay. Prabir still didn’t feel safe sitting down until he’d sprayed a cordon of insect repellent on the ground; the ants were never content to stay inside the orchids, waiting for easy prey. He wasn’t sure why they didn’t swarm up the trees and take nestlings; maybe they were lacking some crucial adaptation for the task, or maybe it just wasn’t worth the energy.
Grant said, ‘So your whole family was here for three years, from 2010? Was your sister born on the island?’
He laughed. ‘We weren’t quite that isolated. We went to Ambon on the ferry four times a year. And we flew down to Darwin for the birth.’
‘Still, it must have been a rough place to raise a young child.’ Grant added hastily, ‘I’m not criticising your parents. I’m just impressed that they could cope.’
Prabir shrugged. ‘I suppose I took that for granted. I mean, the people in small villages on the other islands had better access to transport, clinics they could get to, and so on. But we had a satellite link, which made it easy to forget the distance. I even had lessons from a school in Calcutta; they’d set up a net service for kids in remote villages, but I could join in just as easily.’
‘So at least you had some friends your own age through the net.’
‘Yeah.’ Prabir shifted his position on the rock, suddenly uncomfortable. ‘What about you? What were your school days like?’
‘Mine? Very ordinary.’ Grant fell silent for a while, then she took out her camera and began scanning the branches around them.
She said, ‘The butterflies spend a lot of their time quite high in the canopy. Maybe they lay their eggs there.’ She lowered the camera and asked casually, ‘What are you like at climbing trees?’
‘Seriously out of practice.’
‘It’s like riding a bicycle. You never forget.’
Prabir gave her a stony look. ‘You’re the field biologist, remember? I’m the desk zombie. And I don’t care how ancient you are: you’re twice as fit as I am.’
‘You put that so gallantly.’
Prabir said flatly, ‘I’m not doing it! The deal we made in Ambon—’
Grant nodded effusively. ‘OK, OK! I only asked because I’m not used to judging the strength of the branches of these species. I thought you might be more confident, since you must have climbed them as a kid. I’ll go back to the boat and get a rope—’
‘A rope? You’re not serious?’
‘I had a bad experience in Ecuador,’ she admitted. ‘I broke a lot of bones. So I’m ultra-careful now.’
Prabir’s resentment faded. There was a principle at stake, but he didn’t want to be petty and sadistic. ‘I’ll do it, but you have to pay me. Ten dollars a tree.’
Grant considered this. ‘Make it twenty. I’ll feel better.’
‘With a conscience like that, who needs labour laws?’
Grant selected a nutmeg tree. Prabir took off his boots and rolled up his trouser legs. He hesitated, unsure how to begin. The lowest branch of this tree was just above his head; he must have been able to scale a sheer trunk once, gripping the bark with his arms and legs — he’d even climbed coconut palms — but he felt certain he’d make a fool of himself if he tried that now.
He grabbed the branch and raised himself up, then hooked his feet around it and hung sloth-like for a while before figuring out how to right himself. It was a clumsy start, but once he was standing squarely on the branch, with a firm grip on the next one up, he was elated. The scent of the bark, the feel of it against his soles, was utterly familiar; even the view straight across into the other trees was far closer to anything he remembered than the view from the ground. He glanced down at Grant, not wanting to lose perspective, not wanting to be drawn back too strongly.
She shaded her eyes and looked up at him. ‘Be careful!’
He took a few steps along the branch, feeling it flex, trying to recalibrate his old instincts for his adult weight. He called down, ‘I promise you, I have no intention of breaking my neck for a caterpillar.’
He scoured the clusters of leaves hanging around him for signs of larval feeding, but there was nothing. He climbed higher. Fruit pigeons fled as he approached, a rush of air and a blur of motion. There were foul-smelling beetles on the trunk, but they scurried away from the repellent. There’d been pythons in the trees once, but even the lowest branches wouldn’t have taken the weight of anything remotely like the one he’d met in the mangrove swamp; as long as he didn’t panic and fall to his death, he probably had nothing to fear from its tree-dwelling cousins. Assuming they hadn’t acquired venom.
Twenty metres up, Prabir found something hanging from a slender branch. At first glance he’d mistaken it for a nutmeg fruit, but then a hint of unexpected structure had made him look again. When he was close enough to examine it properly, he found a butterfly, wings folded, suspended from the branch. It had to be a pupa, but it looked more like a tiny sleeping bat than an insect about to emerge from metamorphosis — and it still looked more like a nutmeg fruit than anything else. He touched it warily; it even felt like a nutmeg fruit.
He took out his notepad and recorded some vision, to document the attachment method before he broke the pupa free. The silk girdle around the bulk of the insect was virtually undetectable, the colour matched so well; the short length anchoring it to the branch looked exactly like a stalk. He sent the images down to Grant, and spoke to her through the notepad; it was easier than shouting.
‘What do you make of that? Pretty good camouflage, at the risk of being eaten by mistake.’
‘Maybe they smell bad to the fruit pigeons,’ Grant suggested.
‘Why not just — oh, forget it.’ Whatever anything did, why not do it differently? It was frozen history, not rational design. He broke the pupa free, and dropped it in his backpack. ‘I’ll go up one more level, just to see if there are any larvae.’
‘Are you sure it’ll take your weight?’
The next branch above him was barely chest high now. He wrapped his arms around it and lifted his feet off the one below. ‘Yes, I’m sure.’
He clambered up. He had a firm hold and a secure footing, but he could feel the top of the tree swaying, and the branches around him had thinned enough to make him feel exposed. Looking sideways through the forest at this level, the distant branches appeared uncannily like the struts for some elaborate geodesic folly. Maybe the Stetsoned entrepreneurs who’d followed the expedition down from Ambon could anchor a perspex roof to all this scaffolding, and turn the whole island into an exhibition centre.
He looked down and saw the ruins of the kampung.
A wave of vertigo swept over him, but he kept his grip on the branch beside him. The centre of the kampung had been reclaimed by the forest, but the trees couldn’t quite obscure the roofs of the huts: the matt-grey photovoltaic surface was still visible through a thin layer of creepers. The buildings had all become badly skewed, but none of them appeared to have collapsed completely. The six huts had been arranged in a regular hexagon, and in their current state he couldn’t tell them apart; with the path from the beach erased there were no cues to enable him to orient the view.
He looked away, remembering his purpose. There wasn’t much foliage around him, but he examined it dutifully. Then he spoke into his notepad.
‘There’s nothing else here. I’m coming down.’
Three more trees yielded five more pupae, but still no sign of the larval stage. It was mid-afternoon; Grant decided there was no point looking further. Prabir was dripping with sweat, and itching from all the contact with bark and sap. When they reached the beach, he handed his samples to Grant and swam out to the reef and back. After the heat of the forest, the water was glorious beyond belief.
He collected his clothes from the beach and waded back to the boat. As he climbed up on to the deck, Grant met him with the latest news from Brazil. ‘They’ve copied whole, purified pigeon chromosomes, using just SPP,’ she said. ‘And the error rate was the same as mine, for the cultured cells.’
It took Prabir a moment to interpret this result. ‘So there is no second protein after all?’
‘Apparently not,’ Grant concurred. ‘SPP alone in a test tube does just as good a job as SPP in an intact cell, if and only if the sequence being copied is the same. Which shows that these changes aren’t errors at all. Or at least, they’re not just random copying mistakes. They must depend in some way on the sequence itself.’
Prabir pondered this. ‘The pigeon genome has probably been copied in the presence of SPP dozens of times. So whatever transformation SPP causes must be convergent: the genome must change less and less with each iteration, until by now it’s virtually stable under the process.’
Grant nodded. ‘Whereas there’s no reason at all why the test sequences they first tried copying would have been stable. Randomly chosen input sequences would have undergone apparently random changes.’
Prabir had a minor epiphany. ‘And all the different fruit pigeons on Banda that ended up looking identical — the process must also be convergent for sufficiently similar genomes. Not only is there a stable endpoint for a given starting point, but similar starting points — closely related species — get dragged towards the same endpoint.’ He beamed with delight. ‘It all makes sense!’
Grant was pleased, but slightly less rapturous. ‘Except we still don’t know what SPP actually does, or how it’s doing it.’
‘But the Brazilians have all the information they need to crack this now, don’t they? They just have to look more closely at their model.’
‘Maybe. For a molecule as large as a protein you can never solve the equations for its shape and binding properties exactly, and it can be hard to choose a set of approximations that only cause trivial discrepancies. They’ve already tried simulating the pigeon chromosome being copied by SPP, and the simulation produced exactly the same error rate as for any other sequence.’
Prabir winced. ‘So their model has just proved that it’s missing the most important subtlety of the real protein.’
Grant didn’t see it quite so bleakly. ‘Missing it now, but they might yet be able to capture it with a little fine-tuning. At least they know what they’re aiming for, what they need to get right.’
Prabir said, ‘OK. So what do we do next?’ Grant had been posting all their results on the net, stating precisely where they’d been collecting their samples; the expedition biologists would already know that there was no need for anyone else to come here. So long as Grant didn’t cut corners.
She said, ‘I’ll have a proper look at these pupae, see what that tells us. I don’t know whether it’s worth going back to hunt for the larvae; I mean, the life cycle is of interest in itself, but larvae don’t make germ cells.’
Prabir filled a bucket with sea water and set about washing his sap-stained clothes, while Grant went for a swim. The travel shop in Toronto had sold him a detergent with enzymes that worked in the presence of salt; as long as you didn’t leave it too late you could remove almost anything with the stuff.
When he walked back into the cabin to get fresh water for rinsing, he glanced at the wire cage holding the adult butterflies they’d captured.
There was a pupa, similar to the ones he’d collected in the forest, hanging from the top of the cage. Except it couldn’t be a pupa. The adults had only been there for a day; at most they might have laid eggs. Grant had been in the cabin twenty minutes before. This had happened since then.
Prabir counted the adults. One of them was missing.
He ran out on deck. ‘Martha! You have to see this!’
She was halfway to the reef. ‘See what?’
‘The butterflies.’
‘What about them?’
‘You won’t believe me if I tell you. You have to see it for yourself.’
Grant turned back towards the boat. She followed him into the cabin, dripping. Prabir watched her expression go through several changes.
He said, ‘There’s something I’ve been wanting to try, if you’ll let me.’
‘I’m listening.’
He picked up one of the dormant adults he’d taken from the forest. ‘This insect hangs there, looking like a nutmeg fruit, unable to fly away. So presumably it has some defence: it must smell bad, or taste bad, to the birds that would otherwise want to eat it on sight.’
‘Presumably.’
Prabir approached the cage where they’d placed the fruit pigeons, and gave Grant a questioning look.
She said, ‘Go ahead, please. I want to see this too.’
He opened the door just wide enough to toss the dormant adult on to the floor of the cage. All of the fruit pigeons rushed forward; one of them managed to shoulder the rest aside and grab the insect. The bird stretched its jaws to their full extent and swallowed the sleeping butterfly whole.
Grant sat down heavily on one of the stools. After a long silence, she declared, ‘Maybe there’s a parasitic larval stage. Maybe the adults don’t lay their fertilised eggs; maybe they’re incubated inside the pigeons, after the adults act as a lure.’
‘And that’s why we’ve seen no larvae?’
‘Maybe.’ Grant stretched her arms and leant back on the stool. ‘I suppose it could burrow out through the skin, but I’m beginning to have visions of sifting through a large pile of pigeon shit.’
Prabir walked over to the butterfly cage. They’d placed some foliage in the bottom, but there’d been no elevated twigs or branches from which the would-be martyr could hang itself. He squatted down to try to get a better view of it, and saw a long string of dark-grey beads sticking to the underside of one of the leaves.
He said, ‘Was this foliage clean when you put it in the cage?’
‘I believe so. Why?’
‘I think I’ve just found some butterfly eggs.’
Prabir lay awake, listening to the waves breaking on the reef. The eggs would allow them to observe every stage of the butterfly, but that still wouldn’t be enough. The butterfly’s genome would be stable now; only samples from the kampung could show the way the São Paulo protein had changed it, from generation to generation, twenty years before. They needed to extract every clue the island held; if they didn’t finish the job properly, the expedition would follow them here.
He went into the cabin and woke Grant, calling out to her from the doorway. Her bunk was hidden in shadows, but he heard her sit up. ‘What is it?’
He explained what he’d seen from the treetops. ‘I know where it is now. I can get to it from the beach.’
She hesitated. ‘Are you sure you want to do this? You could draw me a map, I could go by myself.’
Prabir was tempted. The place meant nothing to her: she could walk in and take whatever she needed, ransacking the site unflinchingly, immune to its history.
But this was his job. He couldn’t claim to be sparing Madhusree the pain of returning, only to hand the task over to a stranger.
‘I’d rather go alone.’
Grant said decisively, ‘We’ll go together, first thing tomorrow. I promised you after the mangrove swamp: we won’t get separated again.’