Authors: Greg Egan
This virtual ball-and-stick model was easy to work with -- but its placid behavior in her hands had nothing to do with the physics of the Autoverse, temporarily held in abeyance. Only when she released her grip was the molecule allowed to express its true dynamics, oscillating wildly as the stresses induced by the alteration were redistributed from atom to atom, until a new equilibrium geometry was found.
Maria watched the delayed response with a familiar sense of frustration; she could never quite resign herself to accepting the handling rules, however convenient they were. She'd thought about trying to devise a more authentic mode of interaction, offering the chance to feel what it was "really like" to grasp an Autoverse molecule, to break and re-form its bonds -- instead of everything turning to simulated plastic at the touch of a glove. The catch was, if a molecule obeyed only Autoverse physics -- the internal logic of the self-contained computer model -- then how could she, outside the model, interact with it at all? By constructing little surrogate hands in the Autoverse, to act as remote manipulators? Construct them out of
what?
There were no molecules small enough to build anything finely structured, at that scale; the smallest rigid polymers which could act as "fingers" would be half as thick as the entire
nutrose
ring. In any case, although the target molecule would be free to interact with these surrogate hands according to pure Autoverse physics, there'd be nothing authentic about the way
the hands themselves
magically followed the movements of her gloves. Maria could see no joy in simply shifting the point where the rules were broken -- and the rules had to be broken, somewhere. Manipulating the contents of the Autoverse meant violating its laws. That was obvious . . . but it was still frustrating.
She saved the modified sugar, optimistically dubbing it
mutose.
Then, changing the length scale by a factor of a million, she started up twenty-one tiny cultures of
Autobacterium lamberti,
in solutions ranging from pure
nutrose,
to a fifty-fifty mixture, to one hundred percent
mutose.
She gazed at the array of Petri dishes floating in the workspace, their contents portrayed in colors which coded for the health of the bacteria. "False colors" . . . but that phrase was tautological. Any view of the Autoverse was necessarily stylized: a color-coded map, displaying selected attributes of the region in question. Some views were more abstract, more heavily processed than others -- in the sense that a map of the Earth, color-coded to show the health of its people, would be arguably more abstract than one displaying altitude or rain-fall -- but the real-world ideal of an unadulterated, naked-eye view was simply untranslatable.
A few of the cultures were already looking decidedly sick, fading from electric blue to dull brown. Maria summoned up a three-dimensional graph, showing population versus time for the full range of nutrient mixtures. The cultures with only a trace of the new stuff were, predictably, growing at almost the pace of the control; with increasing
mutose
substitution the ascent gradually slowed, until, around the eighty-five percent line, the population was static. Beyond that were ever steeper trajectories into extinction. In small doses,
mutose
was simply irrelevant, but at high enough concentrations it was insidious: similar enough to
nutrose
--
A.
lamberti's
usual food -- to be taken part-way through the metabolic process, competing for the same enzymes, tying up valuable biochemical resources . . . but eventually reaching a step where that one stray
blue-red
spike formed an insurmountable barrier to the reaction geometry, leaving the bacterium with nothing but a useless byproduct and a net energy loss. A culture with ninety percent
mutose
was a world where ninety per cent of the food supply had no nutritional value whatsoever -- but had to be ingested indiscriminately along with the worthwhile ten percent. Consuming ten times as much for the same return wasn't a viable solution; to survive in the long term,
A.
lamberti
would have to chance upon some means of rejecting
mutose
before wasting energy on it -- or, better still, find a way to turn it back into
nutrose,
transforming it from a virtual poison into a source of food.
Maria displayed a histogram of mutations occurring in the bacteria's three
nutrose epimerase
genes; the enzymes these genes coded for were the closest things
A. lamberti
had to a tool to render
mutose
digestible -- although none, in their original form, would do the job. No mutants had yet persisted for more than a couple of generations; all the changes so far had evidently done more harm than good. Partial sequences of the mutant genes scrolled by in a small window; Maria gazed at the blur of codons, and mentally urged the process on -- if not straight toward the target (since she had no idea what that was), then at least . . .
outward,
blindly, into the space of all possible mistakes.
It was a nice thought. The only trouble was, certain portions of the genes were especially prone to particular copying errors, so most of the mutants were "exploring" the same dead ends again and again.
Arranging for
A.
lamberti
to mutate was easy; like a real-world bacterium, it made frequent errors every time it duplicated its analogue of DNA. Persuading it to mutate "usefully" was something else. Max Lambert himself -- inventor of the Autoverse, creator of
A.
lamberti,
hero to a generation of cellular-automaton and artificial-life freaks -- had spent much of the last fifteen years of his life trying to discover why the subtle differences between real-world and Autoverse biochemistry made natural selection so common in one system, and so elusive in the other. Exposed to the kind of stressful opportunities which
E.
coli
would have exploited within a few dozen generations, strain after strain of
A.
lamberti
had simply died out.
Only a few die-hard enthusiasts still continued Lambert's work. Maria knew of just seventy-two people who'd have the slightest idea what it meant if she ever succeeded. The artificial life scene, now, was dominated by the study of Copies -- patchwork creatures, mosaics of ten thousand different
ad hoc
rules . . . the antithesis of everything the Autoverse stood for.
Real-world biochemistry was far too complex to simulate in every last detail for a creature the size of a gnat, let alone a human being. Computers
could
model all the processes of life -- but not on every scale, from atom to organism, all at the same time. So the field had split three ways. In one camp, traditional molecular biochemists continued to extend their painstaking calculations, solving Schrödinger's equation more or less exactly for ever larger systems, working their way up to entire replicating strands of DNA, whole mitochondrial sub-assemblies, significant patches of the giant carbohydrate chain-link fence of a cell wall . . . but spending ever more on computing power for ever diminishing returns.
At the other end of the scale were Copies: elaborate refinements of whole-body medical simulations, originally designed to help train surgeons with virtual operations, and to take the place of animals in drug tests. A Copy was like a high-resolution CAT scan come to life, linked to a medical encyclopedia to spell out how its every tissue and organ should behave . . . walking around inside a state-of-the-art architectural simulation. A Copy possessed no individual atoms or molecules; every organ in its virtual body came in the guise of specialized sub-programs which knew (in encyclopedic, but not atomic, detail) how a real liver or brain or thyroid gland functioned . . . but which couldn't have solved Schrödinger's equation for so much as a single protein molecule. All physiology, no physics.
Lambert and his followers had staked out the middle ground. They'd invented a new physics, simple enough to allow several thousand bacteria to fit into a modest computer simulation, with a consistent, unbroken hierarchy of details existing right down to the subatomic scale. Everything was driven from the bottom up, by the lowest level of physical laws, just as it was in the real world.
The price of this simplicity was that an Autoverse bacterium didn't necessarily behave like its real-world counterparts.
A.
lamberti
had a habit of confounding traditional expectations in bizarre and unpredictable ways -- and for most serious microbiologists, that was enough to render it worthless.
For Autoverse junkies, though, that was the whole point.
Maria brushed aside the diagrams concealing her view of the Petri dishes, then zoomed in on one thriving culture, until a single bacterium filled the workspace. Color-coded by "health," it was a featureless blue blob; but even when she switched to a standard chemical map there was no real structure visible, apart from the cell wall -- no nucleus, no organelles, no flagella;
A. lamberti
wasn't much more than a sac of protoplasm. She played with the representation, making the fine strands of the unraveled chromosomes appear; highlighting regions where protein synthesis was taking place; rendering visible the concentration gradients of
nutrose
and its immediate metabolites. Computationally expensive views; she cursed herself (as always) for wasting money, but failed (as always) to shut down everything but the essential analysis software (and the Autoverse itself), failed to sit gazing into thin air, waiting patiently for a result.
Instead, she zoomed in closer, switched to atomic colors (but left the pervasive
aqua
molecules invisible), temporarily halted time to freeze the blur of thermal motion, then zoomed in still further until the vague specks scattered throughout the workspace sharpened into the intricate tangles of long-chain lipids, polysaccharides, peptidoglycans. Names stolen unmodified from their real-world analogues -- but screw it, who wanted to spend their life devising a whole new biochemical nomenclature? Maria was sufficiently impressed that Lambert had come up with distinguishable colors for all thirty-two Autoverse atoms, and unambiguous names to match.
She tracked through the sea of elaborate molecules -- all of them synthesized by
A.
lamberti
from nothing but
nutrose, aqua, pneuma,
and a few trace elements. Unable to spot any
mutose
molecules, she invoked
Maxwell's Demon
and asked it to find one. The perceptible delay before the program responded always drove home to her the sheer quantity of information she was playing with -- and the way in which it was organized. A traditional biochemical simulation would have been keeping track of every molecule, and could have told her the exact location of the nearest altered sugar almost instantaneously. For a traditional simulation, this catalogue of molecules would have been the "ultimate truth" -- nothing would have "existed," except by virtue of an entry in the Big List. In contrast, the "ultimate truth" of the Autoverse was a vast array of cubic cells of subatomic dimensions -- and the primary software dealt only with these cells, oblivious to any larger structures. Atoms in the Autoverse were like hurricanes in an atmospheric model (only far more stable); they arose from the simple rules governing the smallest elements of the system. There was no need to explicitly calculate their behavior; the laws governing individual cells drove everything that happened at higher levels. Of course, a swarm of demons could have been used to compile and maintain a kind of census of atoms and molecules -- at great computational expense, rather defeating the point. And the Autoverse itself would have churned on, regardless.
Maria locked her viewpoint to the
mutose
molecule, then restarted time, and everything but that one hexagonal ring smeared into translucence. The molecule itself was only slightly blurred; the current representational conventions made the average positions of the atoms clearly visible, with the deviations due to bond vibration merely suggested by faint ghostly streaks.
She zoomed in until the molecule filled the workspace. She didn't know what she was hoping to see: a successful mutant
epimerase
enzyme suddenly latch onto the ring and shift the aberrant
blue-red
spike back into the horizontal position? Questions of probability aside, it would have been over before she even knew it had begun. That part was easily fixed: she instructed
Maxwell's Demon
to keep a rolling buffer of a few million clock ticks of the molecule's history, and to replay it at a suitable rate if any structural change occurred.
Embedded in a "living" organism, the
mutose
ring looked exactly the same as the prototype she'd handled minutes before: red, green and blue billiard balls, linked by thin white rods. It seemed like an insult for even a bacterium to be composed of such comic-book molecules. The viewing software was constantly inspecting this tiny region of the Autoverse, identifying the patterns that constituted atoms, checking for overlaps between them to decide which was bonded to which, and then displaying a nice, neat, stylized picture of its conclusions. Like the handling rules which took this representation at face value, it was a useful fiction, but . . .
Maria slowed down the Autoverse clock by a factor of ten billion, then popped up the viewing menu and hit the button marked RAW. The tidy assembly of spheres and rods melted into a jagged crown of writhing polychromatic liquid metal, waves of color boiling away from the vertices to collide, merge, flow back again, wisps licking out into space.