“I’m worried,” she said at last. “And I want to talk to you first because I don’t want to turn this into a fight between Ahmed and Arkasha. It’s too important.”
“What’s too important?”
“Ahmed has been after me to tell him that this sickness is some kind of bioweapon. He wants to thaw out the tacticals.”
“Oh God.”
“That’s about what I said when he sprang it on me.”
“Well,” Arkady said, beginning to think through the implications of Ahmed’s idea. “ Is it?”
Aurelia opened her mouth, then closed it without answering. “Arkasha doesn’t think so. As far as I can make out, he thinks we’ve just walked into the terraforming cross fire. God knows it wouldn’t be the first time. First survey mission I crewed on was cleanup for a team that lost all but two members to some kind of hypermutating fungus before they could even figure out what hit them. And Arkasha is the one looking at the viral payload. I’m just trying to sort out the vector of infection. Which, if you ask me, amounts to MotaiSyndicate running an outrageously unethical immunological experiment on the rest of us poor slobs.” She kicked at the grass in frustration. “God, I wish this was a Rostov mission!”
They walked along in silence, Arkady matching Aurelia’s longlegged stride without thought or effort. She had a point, he reflected. “You still haven’t said what you think about Ahmed’s bioweapon idea.”
“It’s possible, of course. Anything’s possible.” She plucked one of the many-petaled blue flowers that had carpeted the pasture during the recent weeks of sun and began tearing the petals off it in an absentmindedly savage game of she-loves-me-not.
“Then you think it evolved here naturally?”
“No. And no, I can’t tell you why.” She looked down at the flower’s dismembered corpse, frowning as if she’d only just realized the havoc her fingers were wreaking. “It just…it just feels wrong.”
“How?”
“I don’t know.” She turned to face him, looking young and scared and nothing like her usual confident self. Behind her the long pasture ran away toward the hidden river, and the silver grass rippled like the fur of some sleeping beast. “It’s like…it’s like a real frog in an imaginary garden.”
And no matter what he did, Arkady couldn’t get her to say what she meant by those words…or even whether she knew that there was no such thing as a real frog anymore.
Arkasha went down with the virus the next day, and by nightfall he was running a dangerously high fever. The sickness was quirky that way; one person’s symptoms might be merely annoying, while the next person might run a fever that had Aurelia talking darkly about the low survival rates for prophylactic cryo. Arkady and Arkasha were a case in point. Arkady’s brush with the disease had been so mild that he still wasn’t sure if he had escaped it altogether or simply failed to notice it amid the general exhaustion and panic. But Arkasha went down hard.
Arkady nursed his pairmate through seventy-two hours of violent chills and fevers, scrupulously following all Aurelia’s instructions. On the evening of the third day he came back from his first hot meal in days to find Arkasha’s bed empty.
He finally tracked his sib down in the first place he should have looked for him: the lab. Arkasha was still haggard with exhaustion and dehydration. But he was clean and shaved and neatly dressed…and doggedly determined to get back to work.
“Are you sure you’re strong enough to be out of bed already?” Arkady asked worriedly.
“No. But I needed to check on something. I had an idea while I was sick. Something about this virus was ringing a bell somewhere, and I finally remembered what it was. Ever heard of Turing Soup?”
Arkady blinked in surprise. “As in Alan Turing?”
“Yep. I think that’s what we’ve caught. I can’t explain how it got here or who spliced it but at least I think I know what they were trying to accomplish.”
“Aurelia said you weren’t sure it wasdesigned.”
“I wasn’t when I talked to her.” He cocked a sharp eye at Arkady. “Why was she talking to you about that? Did she ask you to stop me from insulting Captain Bligh’s breadfruit?”
Arkady laughed in spite of himself. “Is that his new nickname?”
“Well, it’s what I call him. I can’t repeat what Aurelia calls him within range of your delicate ears.”
“Don’t be mad at her for talking to me. She likes you. She just doesn’t want to watch you make trouble for yourself.”
“I know. And I appreciate it. And I’m sorry about what I said after the last consult. I overreacted. It just…brought back bad memories.”
Arkasha rubbed a hand across his forehead and sat down a bit limply. He still looked feverish to Arkady, and not just with the fever of excitement.
“So anyway. The virus. This is still just in the region of wild surmise. But I think it’s an evolutionary search algorithm. Fontana, the human who thought up the Turing Soup idea, spent his whole life working on the relationship between genetic robustness and evolvability. In other words, if species need to change rapidly to respond to changes in their environment, then why are most evolutionarily successful organisms so genetically resistant to change? What’s the adaptive value of all the epistatic effects and redundancy that UN-based commercial splicers are always deleting from their genomes and we’re always trying to preserve? Fontana’s big idea was something he called neutralnetworks. I remember neutral networks from first-year genetic engineering. It’s central to understanding how genotype space maps onto phenotype space: how DNA turns the biological equivalent of a computer program into an actual living organism. It’s also why designers always run into those ‘you can’t get there from here’ design problems. You know: the changes that look like minor tweaks but turn out to involve so many splices that all have so many unintended side effects that you can’t make the ‘tweak’ without stripping the whole geneset down to its bolts and starting over again.”
Arkady nodded. This was a familiar problem for Syndicate design teams, and a major reason for the slow, cautious, incremental changes within genelines. The pre-Breakaway corporate genetic engineers had been far bolder; but they’d assumed cull rates for their company-owned constructs that even MotaiSyndicate would have found ethically indefensible.
“So that’s one of the first lessons in genetic engineering: Just because two organisms ‘look’ the same doesn’t mean their genesets look the same. It just means that their DNA inhabits the same neutral network. And one of the basic truisms of evolutionary genetics is that the most successful species usually have the largest neutral networks. Fontana theorized that this was because neutral networks were nature’s way of minimizing the chances of a you-can’t-get-there-from-here problem. He explained how neutral networks do that by talking about maps of old Europe on Earth. Which makes sense, I guess, since neutral networks are all about the importance of boundaries and territory. Imagine you’re walking around some country. France, let’s say. But you want to get to Germany. Well, if you’re walking around somewhere in the middle of France, it’s going to take a lot of steps to get to Germany…steps that, in the mutational context, are all fraught with an overwhelming risk of producing nonviable phenotypes. But if you happen to be exactly on the border between the two countries, all you need to do is take one easy step and presto, you’re in Germany. And the bigger your country is, the longer your borders are, and the more places you canget to in just one step. Fontana called those border crossings—single mutations that shift an organism into a new phenotype—gateway mutations. The bigger the neutral network, the more gateway mutations. The more gateway mutations, the less risk of a you-can’t-get-there-from-here problem…known in the real world as an extinction event.”