Teranesia

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 Sao 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 Sao 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 Sao 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 Sao 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 Sao Paulo gene pluck?

Those that made as many copies of the Sao 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.’