Several decades later, the searcher arrived at the fourth planet of a not-too-distant star. Turle was a dead world by that time, the Borijan civilization gonebut the programs constituting the Searcher's Supervisor knew nothing about that.
It wasn't much of a world to brag about: an airless, lifeless ball of eroded rock formations, debris from ancient meteorite impacts, and wastes of volcanic ash and dust. Certainly it fell far short of meeting the criteria that Sarvik had specified for the kind of place he and his friends would want to inhabit, and so the command to reactivate them and switch to the alternative manufacturing procedure was not issued. But the orbital probes and surface landers found a crust rich in the kind of minerals the Searcher's regular routine called for, and the Supervisor initiated the descent routine.
A standard robot workforce was deployed to feed ores and materials back to where others had begun building a pilot extraction plant. A parts-making facility was added next, followed by a parts-assembly facility, and step by step the pilot plant grew itself into a general-purpose factory, complete with its own control computers. The master programs from the ship were copied into the factory's computers, which thereupon took charge of surface operations. The factory then began making more robots.
Time passed, the factory hummed, and the robot population grew in number and variety. Maintenance robots took care of stoppages and routine wear in the factory; troubleshooting programs tracked down the causes of production rejects; breakdown teams brought in malfunctioning machines for repair; and specialized scavenging robots roamed in search of wrecks, write-offs, and any other sources of parts suitable for recycling.
When the operation reached a critical size, a mixed workforce detached itself and migrated a few miles away to build a second factory, a replica of the first, using materials supplied initially from Factory One. As this self-replicating pattern spread, production commenced of products and robot freighters to carry them back to the extinct civilization that would never need them. After verifying that all was well and subjecting itself to a thorough overhaul, the Searcher launched itself back into space to seek more worlds on which to repeat the cycle.
Fifty years later, the Searcher was approaching a hot bluish-white star with a mass of more than a dozen times Kov's. It so happened that this was one of the last massive stars to go supernova in the chain that had rippled through the cluster surrounding Kov and put an end to the Borijans and their worries about mortality.
The Searcher's hull survived the heat and radiation blast more or less intact, but secondary X rays and high-energy particles flooded the interior, wreaking havoc with its electronics. With its navigation system disrupted and many of its programs obliterated or corrupted, the Searcher veered away and disappeared back into interstellar space. One of the faint specks now lying ahead of it was a yellow-white dwarf star a thousand light-years away. It, too, possessed a family of planets, and on the third of them, the descendants of a line of semi-intelligent apes had tamed fire and were beginning to experiment with tools chipped laboriously from stone.
A hundred thousand years after its encounter with the supernova, the Searcher drifted into the outer regions of the solar system. The few of its long-range sensors that were still functional fixed upon the planet-moon system of Saturn, finally singling out Titan. Unable to deploy surveillance satellites or high-altitude probes, the ship went straight into its descent routine and landed on an ice beach by an inlet of a shallow methane sea. It was a bleak, barren, ice-encrusted world, unsuitable either for remote manufacturing or for hosting re-created Borijans, but that was of no consequence since the programs for evaluating the prospects for both kinds of endeavor weren't working. Accordingly, Factory One, with most of its essential functions up and running to at least some degree, took shape on a rocky shelf above the ice beach.
It was when Factory One's Supervisor identified commencement of work on Factory Two as its next assignment that everything went completely wrong. The "How to Make a Factory" file that it signaled for from the ship's data bank included a set of subfiles on "How to Make the Machines Needed to Make a Factory," i.e., robots. Because of corruption in the software, the subfiles containing the robot-manufacturing information, instead of being transmitted to Factory One, were merely relayed through the factory's system and beamed out to the local memories of the robot types to which they pertained. No copies at all were retained in the factory files, and worse still, the originals inside the ship managed to get erased in the process. Eventually the system diagnostics managed to piece together what had happened. The scheduler couldn't schedule anything without manufacturing information, and the only information that now existed for making robots was that contained inside the robots out on the surface. So the Supervisor put out messages telling them to send their manufacturing information back again.
But none of the robots were able to comply. Their local memories were simply not big enough to hold a complete manufacturing subfile. However, different individuals seemed to have collected different pieces of their respective files, and a quick check indicated that most of the information had been preserved among all of them. So the Supervisor retrieved different parts from different sources and tried to fit them back together in a way that made sense, and that was how it arrived at the versions it eventually passed to the scheduler for manufacture.
Unfortunately, the instruction to store this information for future reference got lost somewhere, and the Supervisor had to go through the whole rigmarole again whenever a new batch of a particular robot type was needed. The Supervisor had been written as a self-modifying learning program that would grow unhappy about such an inefficiency and experiment with ways of doing something about it. It found that some of the robots contained about half their respective subfiles, and in some cases the halves were complementary. This meant that a complete copy could be obtained by interrogating just two individuals instead of many. Accordingly, the Supervisor made a note of such "matching pairs" as its sources for servicing future scheduling requests and ignored the others. Thus, the robots started coming off the line with one-half of their "genetic" information included in the programs that were written into them to start them up, and they in turn became the source when more models came to be built later.
The resulting "genomes" were seldom identical, and as a consequence the robots began taking on ever stranger shapes and behaving in strange ways. The majority simply failed to function at all and were broken down again for recycling. Many were genetically incomplete"sterile"and lasted until they wore out, then became extinct. Of those which did reproduce, most did so passively, transmitting their half subfiles to the Supervisor when the Supervisor asked for them.
A few, however, had inherited routines from the ship's software that caused them to lodge requests with the scheduler to schedule more models of their own kindroutines, moreover, that raised the urgency of their requests until they were serviced. These robots reproduced actively: they behaved as if they experienced a compulsion to ensure that their half subfiles were always included in the scheduler's list of things to make next. The robots competing in this way for slots in the production schedules soon overrode the demands for everything else. And this pattern spread through the new factories appearing inland from the rocky coastal shelf.
Resources were scarce everywhere, adding to the competitive pressure. The factory-robot communities that had "appetites" appropriate to their needs and also enjoyed favorable sites usually managed to survive, if not flourish. Factory Ten, for example, was built in the center of a meteorite crater where the impact had exposed metal-bearing bedrock from below the ice. Factory Thirteen occupied a deep fissure and was able to melt a shaft down to access core materials, while Factory Fifteen resorted to building up nuclei by transmutation. But there were many like Factory Nineteen, which ground to a halt half-complete when its drilling robots and transmutation reactors failed to function, and its supply of materials ran out.
The parts-salvaging scavengers, able to locate assemblies suitable for breaking down"digesting"and rebuilding into something useful, assumed a crucial role in shaping the strange metabolism that was coming into being. The piles of assorted junk and broken-down robots were eaten up; the carcasses of defunct factories were eaten up; the Searcher ship, still lying on the ice beach by the methane sea, was eaten up. And when those sources of parts and materials ran low, some of the machines started eating each other.
The scavengers were supposed to discriminate between properly functioning machines and rejects in need of disassembling and recycling. But as with everything else in the mess the project had turned into, this worked with varying success in most cases and sometimes not at all, which meant that some types were likely to attempt the dismantling of a live, walking-around something or other instead of a dead, flat-on-its-back one. The victims who were indifferent to this kind of treatment soon died out, but others evolved fight-or-flight responses to preserve themselves, marking the emergence of specialized prey and predators.
This development was not always advantageous. Factory Fifty, for instance, was consumed by its own offspring, who began dismantling it at its output end as soon as they came off the line and then proceeded to deliver the pieces back to the input end. It slowed to a halt and became plunder for foraging groups from Thirty-six and Fifty-three. The most successful factory-robot organisms protected themselves by producing aggressive armies of "antibody" defenders, which recognized their own factory and its "kind" and left them alone, but attacked any "foreign" models that ventured too close. This gradually became the dominant form of community, usually associated with a distinct territory that its members cooperated in protecting.
The normal Borijan remote manufacturing setup included planetwide communications coverage for coordinating its various operations. In Titan's case, however, no satellites had been put up, and facilities operating on the surface were showing defects of every kind. However, the Borijan engineers had provided a backup method for program and data interchange between the factories and their outside robots in the form of direct physical interconnection. It was much slower than radio, of course, since it required the robots to go physically to the factories for reprogramming and reporting, but in self-sustaining operations of that magnitude far from home, some such protection of the investment was essential. Factory Seventy-three, constructed with no radio capability at all, was started up by programs physically transported from Sixty-six. None of its robots ever used anything but the backup mode, and the descendant factories it spawned continued the tradition. But that very fact meant that foraging parties were able to roam farther afield, beyond line-of-sight links, and in the process enlarged their catchment areas dramatically.
So the "defect" turned out to be not so much of a defect, after all. Furthermore, continuing selective pressures tended to improve the autonomy of the robots that operated in this fashion. Relying only on their comparatively small local processors, they applied simple solutions to the problems they encountered; but their closely coupled mode of interacting with their surroundings meant that the solutions were applied fast: they evolved efficient "reflexes." The traditional models, by contrast, tied to their larger but remote central computers, could apply more sophisticated methods, but as often as not they applied them too late to derive any benefit. Autonomous operation thus conferred a behavioral superiority that asserted itself as the norm, while use of radio declined in importance and became rare.
The periodic urge that robots felt to communicate genetic half subfiles back to their factories had long become universalancestors not sharing it had left no descendants. Their response to the demise of radio was to evolve a compulsion to journey at intervals back to the places whence they had cometheir "spawning grounds." This in turn posed new challenges to the evolutionary process.
The main problem was that an individual could deliver only half its genome to the factory, with a high risk of its being deleted if the Supervisor encountered overload conditions before another robot of the same basic type arrived with a matching half. The successful response was a new mode of genetic recombination, which, coincidentally, also provided the answer to an "information crisis" that was restricting the pool of genetic variation available for further selection and improvement.
Some mutant forms of robot found that they could save themselves the trouble of long journeys back to factories by satisfying the half-subfile-outputting urge locally with anything that possessed the right electrical connections and compatible internal software, which usually meant another robot of the same basic kind. However, although the robots' memories were getting larger, so were their operating programs, with the result that an acceptor didn't have enough free space to hold an entire genetic subfile. Therefore, the donor's half was accommodated by overwriting nonessential code, which did incur the inconvenience of leaving the "female" with some impairment of agility and defensive abilitybut that was only temporary, since full faculties would be restored when the genetic package was delivered to the factory.
But in return for these complications came the immense benefit that the subfiles delivered to the factories would be complete, ready to be passed instantly to the schedulers, free from the risk of being deleted by overworked Supervisors.
The information crisis that this progression beyond asexual reproduction also solved was a result of inbreeding. The various Supervisors had only the gene pools of their respective tribes available to work with, which made recombination difficult because of the rules imposed by the Borijan programmers. But the robots mixing genes out on the surface knew nothing and cared less about programmers' rules and proceeded to bring half subfiles together haphazardly in ways that the rules didn't permit and the Supervisors could never have conceived of. Most of the combinations that resulted from these experiments were nonviable, but the few that were viable radiated outward functionally in every direction to launch a whole qualitatively distinct, explosive new phase of the evolutionary process.
The demands of the two sexual roles reinforced minor initial differences and brought about a gradual polarization of behavioral traits. Since a "pregnant" female suffered some loss of self-sufficiency for the duration, her chances of success were improved considerably if her mate happened to be of a disposition to stay around and help out for a while, perhaps accompanying her on her journey and protecting their joint genetic investment. Selection tended, therefore, to favor this kind of male and, by the same token, those females who mated with them preferentially. Hence, a female tendency emerged of being "choosy," and in response the males evolved various repertoires of rituals, displays, and demonstrations to improve their eligibility.
The process unfolding on the surface of Titan had thus come to exhibit genetic variability and recombination, competition, selection, and adaptationall the essentials for continuing evolution. The form of lifefor it was, wasn't it?was admittedly strange from the terrestrial viewpoint, with the individuals that it included sharing common external reproductive, digestive, and immune systems instead of separate internal ones . . . and, of course, there was no complicated carbon chemistry figuring in the scheme of things. But then, what was there, apart from chauvinism, to say that it shouldn't have been so?
And over all that time some copies of the coded configurations that preserved the essence of the twelve Borijan personae from the distant past were passed down through the generations, millennium after millennium, never to be expressed in any functioning or physical form.
A million years passed. Then, one day, a robot craft from a civilization born of a different life-form appeared over Titan's canopy of rust-red cloud. The pictures and data returned by the probes that it sent down revealed a world stranger than anything its builders had ever seen before. Shortly afterward, astronomically speaking, the Orion followed, bringing with it descendants of the line of semi-intelligent apes of long ago to investigate.