d more diversity。 By a couple of hundred million years ago there are large plants and animals； plex creatures； dinosaurs。 In all this； man's a lateer： four million years ago； upright apes。 Two million years ago； early human ancestors。 Thirty…five thousand years ago； cave paintings。 The acceleration was dramatic。 If you pressed the history of life on earth into twenty…four hours； then multicellular organisms appeared in the last twelve hours； dinosaurs in the last hour； the earliest men in the last forty seconds； and modern men less than one second ago。 It had taken two billion years for primitive cells to incorporate a nucleus； the first step toward plexity。 But it had taken only 200 million years…one…tenth of the time…to evolve multicellular animals。 And it took only four million years to go from small…brained apes with crude bone tools to modern man and genetic engineering。 That was how fast the pace had increased。
This same pattern showed up in the behavior of agent…based systems。 It took a long time for agents to 〃lay the groundwork〃 and to acplish the early stuff； but once that was pleted； subsequent progress could be swift。 There was no way to skip the groundwork； just as there was no way for a human being to skip childhood。 You had to do the preliminary work。 But at the same time； there was no way to avoid the subsequent acceleration。 It was； so to speak； built into the system。
Teaching made the progression more efficient； and I was sure Julia's teaching had been an important factor in the behavior of the swarm now。 Simply by interacting with it； she had introduced a selection pressure in an organism with emergent behavior that couldn't be predicted。 It was a very foolish thing to do。
So the swarm…already developing rapidly…would develop even more rapidly in the future。 And since it was a man…made organism； evolution was not taking place on a biological timescale。 Instead； it was happening in a matter of hours。
Destroying the swarms would be more difficult with each passing hour。 〃Okay；〃 I said to David。 〃If the swarms are ing back； then we better get ready for them。〃 I got to my feet； wincing at the headache； and headed for the door。 〃What do you have in mind？〃 David said。
〃What do you think I have in mind？〃 I said。 〃We've got to kill these things cold stone dead。 We have to wipe them off the face of the planet。 And we have to do it right now。〃 David shifted in his chair。 〃Fine with me；〃 he said。 〃But I don't think Ricky's going to like it。〃
〃Why not？〃
David shrugged。 〃He's just not。〃
I waited； and said nothing。
David fidgeted in his chair； more and more unfortable。 〃The thing is； he and Julia are； uh； in agreement on this。〃
〃They're in agreement。〃
〃Yes。 They see eye to eye。 I mean； on this。〃
I said； 〃What are you trying to say to me； David？〃
〃Nothing。 Just what I said。 They agree the swarms should be kept alive。 I think Ricky's going to oppose you； that's all。〃
I needed to talk to Mae again。 I found her in the biology lab； hunched over a puter monitor； looking at images of white bacterial growth on dark red media。 I said； 〃Mae； listen； I've talked to David and I need to…uh； Mae？ Have you got a problem？〃 She was looking fixedly at the screen。
〃I think I do；〃 she said。 〃A problem with the feedstock。〃
〃What kind of problem？〃
〃The latest Theta…d stocks aren't growing properly。〃 She pointed to an image in the upper corner of the monitor； which showed bacteria growing in smooth white circles。 〃That's normal coliform growth；〃 she said。 〃That's how it's supposed to look。 But here 。。。〃 She brought up another image in the center of the screen。 The round forms appeared moth…eaten； ragged and misshapen。 〃That's not normal growth；〃 she said； shaking her head。 〃I'm afraid it's phage contamination。〃
〃You mean a virus？〃 I said。 A phage was a virus that attacked bacteria。 〃Yes；〃 she said。 〃Coli are susceptible to a very large number of phages。 T4 phage is of course the most mon； but Theta…d was engineered to be T4…resistant。 So I suspect it's a new phage that's doing this。〃
〃A new phage？ You mean it's newly evolved？〃
〃Yes。 Probably a mutant of an existing strain； that somehow gets around the engineered resistance。 But it's bad news for manufacturing。 If we have infected bacterial stocks； we'll have to shut down production。 Otherwise we'll just be spewing viruses out。〃
〃Frankly；〃 I said； 〃shutting down production might be a good idea。〃
〃I'll probably have to。 I'll try to isolate it； but it looks aggressive。 I may not be able to get rid of it without scrubbing the kettle。 Starting over with fresh stock。 Ricky's not going to like it。〃
〃Have you told him about this？〃
〃Not yet。〃 She shook her head。 〃I don't think he needs more bad news right now。 And besides 。。。〃 She stopped； as if she had thought better of what she was going to say。 〃Besides what？〃
〃Ricky has a huge stake in the success of this pany。〃 She turned to face me。 〃Bobby heard him on the phone the other day； talking about his stock options。 And sounding worried。 I think Ricky sees Xymos as his last big chance to score。 He's been here five years。 If this doesn't work out； he'll be too senior to start over at a new pany。 He's got a wife and baby； he can't gamble another five years； waiting to see if the next pany clicks。 So he's really trying to make this happen； really driving himself。 He's up all night； working； figuring。 He isn't sleeping more than three or four hours。 Frankly； I worry it's affecting his judgment。〃
〃I can imagine；〃 I said。 〃The pressure must be terrible。〃
〃He's so sleep…deprived it makes him erratic；〃 Mae said。 〃I'm never sure what he'll do； or how he'll respond。 Sometimes I get the feeling he doesn't want to get rid of the swarms at all。 Or maybe he's scared。〃
〃Maybe；〃 I said。
〃Anyway； he's erratic。 So if I were you I'd be careful；〃 she said； 〃when you go after the swarms。 Because that's what you're going to do； isn't it？ Go after them？〃
〃Yes；〃 I said。 〃That's what I'm going to do。〃
DAY 6
1：12 P。M。
They had all gathered in the lounge； with the video games and pinball machines。 Nobody was playing them now。 They were watching me with anxious eyes as I explained what we had to do。 The plan was simple enough…the swarm itself was dictating what we had to do； although I was skipping that unfortable truth。
Basically； I told them we had a runaway swarm we couldn't control。 And the swarm exhibited self…organizing behavior。 〃Whenever you have a high SO ponent； it means the swarm can reassemble itself after an injury or disruption。 Just as it did with me。 So this swarm has to be totally； physically destroyed。 That means subjecting the particles to heat； cold； acid； or high magnetic fields。 And from what I've seen of its behavior； I'd say our best chance to destroy it is at night when the swarm loses energy and sinks to the ground。〃
Ricky whined； 〃But we already told you； Jack； we can't find it at night…〃
〃That's right； you can't；〃 I said。 〃Because you didn't tag it。 Look； it's a big desert out there。 If you want to trace it back to its hiding place； you've got to tag it with something so strong you can follow its trail wherever it goes。〃
〃Tag it with what？〃
〃That's my next question；〃 I said。 〃What kind of tagging agents have we got around here？〃 I was greeted with blank looks。 〃e on； guys。 This is an industrial facility。 You must have something that will coat the particles and leave a trail we can follow。 I'm talking about a substance that fluoresces intensely； or a pheromone with a characteristic chemical signature； or something radioactive 。。。 No？〃
More blank looks。 Shaking their heads。
〃Well；〃 Mae said； 〃of course； we have radioisotopes。〃
〃All right； fine。〃 Now we were getting somewhere。
〃We use them to check for leaks in the system。 The helicopter brings them out once a week。〃
〃What isotopes do you have？〃
〃Selenium…72 and Rhenium…186。 Sometimes Xenon…133 as well。 I'm not sure what we've got on hand right now。〃
〃What kind of half…lives are we talking about？〃 Certain isotopes lost radioactivity very rapidly； in a matter of hours or minutes。 If so； they wouldn't be useful to me。 〃Half…life averages about a week；〃 Mae said。 〃Selenium's eight days。 Rhenium's four days。 Xenon…133 is five days。 Five and a quarter。〃
〃Okay。 Any of them should do fine for our purposes；〃 I said。 〃We only need the radioactivity to last for one night； after we tag the swarm。〃
Mae said； 〃We usually put the isotopes in FDG。 It's a liquid glucose base。 You could spray it。〃
〃That should be fine；〃 I said。 〃Where are the isotopes now？〃
Mae smiled bleakly。 〃In the storage unit；〃 she said。
〃Where is that？〃
〃Outside。 Next to the parked cars。〃
〃Okay；〃 I said。 〃Then let's go out and get them。〃
〃Oh； for Christ's sake；〃 Ricky said； throwing up his hands。 〃Are you out of your mind？ You nearly died out there this morning； Jack。 You can't go back out。〃
〃There isn't any choice；〃 I said。
〃Sure there is。 Wait until nightfall。〃
〃No；〃 I said。 〃Because that means we can't spray them until tomorrow。 And we can't trace and destroy them until tomorrow night。 That means we wait thirty…six hours with an organism that is evolving fast。 We can't risk it。〃
〃Risk i