Teranesia

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?’