by Greg Egan
The trouble was, when the São Paulo protein was bound to DNA, many of its bonds had two main eigenstates that were equally probable. This left no choice but to select the state of each bond at random: the software tossed several thousand dice, and singled out a particular conformation of the molecule to analyse. And in the first test tube experiments, nature had appeared to be doing virtually the same thing: when the strands of DNA had been copied with random errors, SPP had seemed to be merely amplifying quantum noise when it chose a different base to add to the new strand. But the near-perfect copying of the fruit pigeon chromosome, and the successive intergenerational changes in the DNA from the Suresh butterfly specimens, showed that something far subtler was going on.
The crucial subtlety, Furtado claimed, was that none of the probabilities that controlled the shape of the protein really were precisely equal. One or the other would always be favoured, though the balance was so fine that the choice would depend, with exquisite precision, on the entire quantum state of the strand of DNA to which the protein was bound. Furtado conjectured that SPP was exploiting this sensitivity to count the numbers of various ‘counterfactual cousins’ of the DNA: similar, but non-identical sequences that might have been produced in its place, if only its recent history of random mutations had been different. If the most numerous cousins dictated the sequence of the new copy of the DNA, that explained why the mutations weren’t random, why they never killed or disadvantaged the organism. They’d been tested, and found to be successful: not in the past, as Grant had hypothesised, but in different quantum histories.
Prabir looked up from the notepad. ‘I don’t know what to say. Nobel prize-winning physicists have been throwing rotten fruit at each other for a hundred years over interpretations of quantum mechanics, and as far as I know they’re still at it. Nobody has ever resolved the issues. If Furtado thinks the Many Worlds Interpretation is right, there’s a long list of famous physicists who’d back him up, so who am I to argue? But drawing information from other histories is something different. Even most believers would tell you it could never be done.’
Grant said, ‘That’s pretty much my own feeling.’ She leant over to see how far he’d read. ‘There’s some interesting speculation later on, suggesting the kind of data analysis the protein could be performing to extract the interference patterns between the DNA and its cousins from all the noise produced by thermal effects. If any of it’s true, though, SPP must have evolved into a veritable quantum supercomputer.’
Prabir scrolled down and glanced over the section she’d described; most of the equations were completely over his head, but there were passages of text he could follow.
Although the Hilbert space in which the pure states reside cannot be reconstructed with certainty, it has been shown theoretically for simpler systems [Deutsch 2012, Bennett 2014] that an exhaustive search for global entropy minima over the unknown degrees of freedom can identify probable candidates in polynomial time by exploiting quantum parallelism.
Could a very bad quantum supercomputer have found a gene for a slightly better one? And so on? Furtado was claiming as much, but in the final section of the article he admitted that it was impossible to prove this directly; modelling any version of the São Paulo protein to the necessary level of precision was out of the question. He was, however, planning an experiment that could falsify his hypothesis: he was synthesising a copy of one of the fruit pigeon chromosomes, right down to the methylation tags. This molecule would be identical to the biological chromosome in both its raw sequence of bases and every known ‘epigenetic’ chemical subtlety, but its quantum state would not be correlated with that of the DNA in any living bird, real or counterfactual. If SPP copied this with the same low error rate as the natural version, Furtado’s flamboyant theory would go down in flames.
‘If this were true,’ Prabir mused, ‘it would explain a lot of things. You yourself admitted that Teranesia looked like a place where relatives of the locals, who’d parted company and co-evolved elsewhere, were being gradually reintroduced. If Furtado is right, that’s exactly what’s happened. Only they parted company when different mutations put them into different quantum histories, and they’re being “reintroduced” via a gene that goes out of its way to steal ideas from the most successful members of the family.’
Grant smiled indulgently. ‘Explain the fruit pigeons, then. And the barbed-wire shrubs. What’s going on with the camouflage, and the thorns?’
Prabir pondered this for a while. ‘It’s a counterfactual defence. Once you have the São Paulo gene, you can block predators that have never even tried to prey on you, in your own history. And so long as you maintain the defence, they won’t bother evolving in that direction, because they can see that there’s no point. It’s like a simple chess program: no elaborate strategies copied from grand masters, just the power to look ahead a few moves and assess the consequences. If brute force computation reveals a strategy – like castling, say – that gives a medium-term advantage over all possible moves by its opponents, the program will use it. And it will never reverse it, even if there’s no immediate threat, because it can look far enough ahead to see that any back-down would be exploited.’
Grant was beginning to look slightly uncomfortable. ‘You don’t seriously believe that’s what’s happening, though?’
‘Absolutely not. He’ll run the experiment on the synthetic chromosome, and prove himself wrong.’
Grant made a half-hearted sound of agreement, as if she was afraid that excessive confidence might be tempting fate.
Prabir said, ‘I meant to ask you: did you get the results of the RNA analysis of the dormant adults?’ The last he’d heard, it had been running overnight.
‘Yeah. There’s a peptide being produced that’s virtually identical to a well-known hormone that puts the adults of certain temperate species of butterflies into diapause when they hibernate over winter. And the alteration in the texture and pigmentation of the wings seems to have followed from a cascade of gene activity very similar to one that happens in ordinary metamorphosis. It’s all pretty much what I’d expected: just a few existing tricks redeployed.’
‘OK. But redeployed to what end? I know it’s pointless now, because the adults have already laid their eggs externally, but could this be a throwback to a species that used to reproduce via parasitic larvae?’ Maybe the gene resurrection idea could still be salvaged, after all.
Grant shook her head. ‘Not unless it’s gone even more awry than that. The males are all doing it too.’
Prabir held the guard rail and pushed against it, trying to unknot his shoulders. ‘If the gene didn’t start off as something every species has for mutation repair, we still have to account for its spread from the butterflies to everything else.’ He turned to Grant, smiling disarmingly, hoping she’d suffer a little more frivolous speculation. ‘Just for argument’s sake: if Furtado was right, maybe the São Paulo gene saw this as an easy way to get copies of itself into the fruit pigeons.’
Grant didn’t respond immediately; Prabir assumed she was thinking up a suitably withering reply.
‘I found something else in the RNA analysis,’ she said.
‘Yeah.’
‘Large amounts of an endonuclease – an enzyme for cutting and splicing DNA – being produced throughout the bodies of the dormant adults. I haven’t characterised it any further yet …’ She trailed off.
Prabir said, ‘But if it’s the right kind of endonuclease, it might be perfect for the job of splicing the São Paulo gene into the genome of the fruit pigeons?’
Grant nodded, and continued reluctantly. ‘The fraction of DNA and endonuclease that survived digestion and entered the bloodstream would always be tiny, though I suppose it could be packaged in something like liposomes to protect it, and help it get absorbed by the wall of the gut. There’s then another hurdle to get the gene into the ovaries or testes. This might be the transmission route, but the whole picture’s not clear, by any means.’
/> Prabir looked back across the water; he could still see Teranesia’s volcanic cone in the distance. ‘Everything else could be a throwback, couldn’t it? If mimcry was once used to get parasitic larvae into the fruit pigeons, then if the genes for that have been reactivated now, pointlessly, in egg-laying females, they might also have been reactivated in males – simply because the switch isn’t functioning properly.’
‘I suppose so.’
‘And there are other uses for endonucleases, aren’t there? It might be a coincidence that the endonuclease gene is switched on at the same time as the others?’
‘It might.’
Prabir laughed suddenly. ‘Listen to me. We’ve been to Teranesia, we’ve been to the source, and I expect everything to fall into place in a day. I’ve gone twenty-one years without an answer. I can wait a little longer.’
He glanced down at the graphic of SPP in Furtado’s article, which was cycling through sixteen of the conformations it could adopt, binding to each of the four bases in the old strand while adding each of the four to the new. Between them, these sixteen simple transformations could generate every conceivable change: as the old strand was broken apart and the new one constructed, the potential existed for the organism to become anything at all.
And from that limitless sea of possibilities, what marvellous inventions did the São Paulo gene pluck?
Those that made as many copies of the São Paulo gene as possible.
They reached the island of the mangroves and made use of the same approach as before, then sailed around the coast inside the reef. As they drew nearer to the point where the expedition had set up camp, Prabir saw that the fishing boat was gone, but another vessel had taken its place alongside the research ship.
They dropped anchor and waded ashore. They were halfway to the camp when a young man appeared on the beach about fifty metres ahead of them, dressed in camouflage trousers, combat boots, and a Chicago Bulls T-shirt. He raised a rifle and aimed it at them, then barked out a series of commands in English.
‘Halt! Put your hands on your heads! Squat down!’
They complied. The man walked up to Prabir and held the rifle to his temple. ‘What are you doing here? Where have you come from?’ Prabir was too agitated to reply immediately, but as he struggled to relax his larynx sufficiently to speak he took some comfort from the realisation that the man was probably not a pirate. Only a soldier would be so interested in their movements, and whatever misunderstanding was provoking his hostility would surely be easy enough to resolve.
Grant explained calmly, ‘I’m a biologist, this is my assistant. I have a permit from the government in Ambon.’
The soldier’s reaction to this last phrase was not encouraging. ‘Pig-fucking ecumenical heretics!’ Prabir’s heart sank. The man was not a Moluccan soldier: he was with the Lord’s Army, West Papua’s born-again Christian militia. Officially, they weren’t even part of that country’s armed forces, though it was widely assumed that they received clandestine government support. They’d been making trouble in Aru for years. But Aru was almost three hundred kilometres east.
‘Where have you been?’ the man demanded.
Prabir said, ‘On the other side of the island.’ If Teranesia’s infamy had spread throughout the region, it might not be wise to admit to having visited the place.
‘You’re lying. Yesterday, there was no sign of your boat.’
‘You must have missed us. We were halfway into the mangroves.’
The man snorted with derision. ‘You’re lying. You come and see Colonel Aslan.’
As they walked through the camp, Prabir saw three more armed men lounging around looking bored, and several of the expedition members standing nervously at the entrances to their tents. The biologists weren’t exactly being guarded like hostages, but this was definitely not a guest/host relationship. There was no sign of Madhusree. Prabir kept telling himself that there was no reason for the soldiers to have harmed anyone, but nor was there any obvious reason for them to be here at all. Maybe there’d been a case that Aru should have joined West Papua at independence – even if that was now about as attractive a prospect as West Bengal being declared a part of Pakistan – but it was hard to imagine what kind of mileage the Lord’s Army expected to gain for the cause by bullying foreigners deep in RMS territory.
The Colonel had taken up office in one of the expedition’s supply tents; Prabir and Grant were made to stand and wait outside in the early-afternoon sun. After twenty minutes, the soldier guarding them muttered something irritably in his native language and went and sat in the shade of a tree, his rifle propped up on one knee to keep it pointing vaguely in their direction.
Prabir whispered, ‘You do know who we’re dealing with?’
‘Yeah, yeah. I’ll be on my best Sunday-school behaviour.’ Grant seemed more weary than afraid, as if this was just another tedious obstacle to get through, no different from slogging through the mangroves. But she’d travelled widely, so perhaps she’d grown accustomed to occasional periods of arbitrary detention.
‘ “Colonel Aslan”’ Do you think he’s a foreign mercenary? It sounds more like a name from central Asia than anything from around here.’
Grant smiled, somewhat condescendingly. ‘I believe it’s now a common choice upon conversion to Christianity all over the planet, at least when the evangelists get their hooks in early enough. Just don’t admit to a fondness for Turkish delight, and you should be OK.’
‘Turkish delight?’
‘Don’t worry. It would take too long to explain.’
A second young soldier emerged from the tent and shot a warning glance at their guard, who leapt to his feet. The two of them escorted Grant and Prabir into the tent, past drums of flour and boxes of toilet paper.
Colonel Aslan turned out to be a muscular Papuan man in his thirties, apparently devoted to the Dallas Cowboys. He was seated behind a desk improvised from crates. When Grant handed over her permit, he smiled graciously. ‘So you’re the famous Martha Grant! I’ve been following your work on the net. You’ve been to the heart of the contagion, and returned to tell the tale.’
Grant replied warily, ‘There’s no evidence that the mutations are contagious.’
‘Yet these creatures turn up hundreds of kilometres away. How do you account for that?’
‘I can’t. It will take time to explain.’
Aslan nodded sympathetically. ‘Meanwhile, my country and my people remain at risk from these abominations. What am I expected to do about that?’
Grant hesitated. ‘The impact on agriculture and health of flora and fauna transported across national borders by inadvertent human actions, or acts of nature, is the subject of a number of treaties. There are international bodies where these issues can be discussed, and any appropriate response coordinated.’
‘That’s a very diplomatic answer. But there are boats weaving back and forth across the Banda Sea as we speak, without regard to anything some subcommittee of the World Health Organisation might have to say on the matter in five years’ time.’
Grant said neutrally, ‘I can’t advise you on this. It’s beyond my expertise.’
‘I understand.’ Aslan nodded at the soldier from the beach, who led Grant out of the tent. Then he turned to Prabir.
‘You accompanied her on this trip?’
‘Yes.’
‘Did you fornicate with her, on the boat?’
Prabir was unsure for a moment that he’d heard correctly. Then he replied icily, ‘I’m not familiar with that dialect of English.’
Aslan was indulgent. ‘Did you have sexual intercourse?’
‘That’s none of your business.’
The soldier who’d remained took a step towards Prabir, holding up his rifle like a club.
Prabir stared down at the tent’s mud-spattered ground sheet. What was going on in these people’s heads? Were they looking for an excuse to brand Grant as promiscuous, so they could rape her with a clear conscience?
>
‘No. We didn’t have sex.’
There was a long silence, then Aslan said calmly, ‘Look at me.’
Prabir raised his eyes reluctantly.
‘Are you a Muslim?’
‘No.’
Aslan seemed disappointed; maybe he’d been hoping to demonstrate his sophistication in the presence of the enemy. ‘Then I won’t ask you to swear on the name of the Prophet. But you’re a healthy young man, and she is a very charming woman.’
‘She is a virtuous married woman.’
‘But you took advantage of her? You raped her?’
Prabir was about to offer an outraged denial, when he realised that there’d be no end to this until Aslan had an explanation for his discomfort at the line of questioning. He looked him in the eye and said, ‘Why would I want to? I’m homosexual.’
Aslan blinked bemusedly, and for a moment Prabir wondered if he only knew derogatory terms and Biblese. Then he spread his arms and proclaimed joyously, ‘Hallelujah! That can be cured!’
Prabir muttered, ‘Not half as easily as Christianity.’
The soldier beside him swung the rifle butt into his temple. Prabir reeled, and fought to keep his balance. But the blow hadn’t been heavy, he wasn’t even bleeding.
‘You can cut off a man’s cock,’ Aslan declaimed, ‘but you can’t cut out his soul.’
Prabir was sorely tempted to improvise a maximally offensive rejoinder involving kuru and communion wafers, but it didn’t seem worth the risk of discovering that this homily was actually a recipe for surgical intervention.
Aslan said mildly, ‘Get him out of here.’
*
Prabir was led to another tent, where the expedition member who’d examined him after the python attack – he thought he remembered Ojany calling her Lisa – took a blood sample from him. She was clearly acting under duress as much as he was, but he’d rather she stuck the hypodermic in his arm than have one of the Lord’s Army do it.
