Critical Threshold

by Brian Stableford

  “It isn’t me,” I said. I was thinking of minds being blown like fuses. But Karen wasn’t. She was thinking about something else.

  “You don’t understand,” she said. “You don’t understand how much Mariel has tied up in this. It’s her chance to employ her talent. It’s her chance to put herself to some use. You ought to be able to figure that. You’re a top-class biologist, an expert on evolutionary ecology. On Earth, how much scope did you have for the exercise of your particular talent? How much would that talent have meant if you’d never had the chance to come out with the Daedalus, to see a whole host of alien evolutions, alien ecologies? This is your fulfillment, Alex. And it’s hers, too. Even more so.

  “On Earth, she was a party trick, a carnival freak. They tried to put her to work, to use her, and they failed. She’s a great lie detector, and maybe she can tell whether people are sick in the head...but she couldn’t ever find a role to play on Earth. You know that. They wouldn’t let her. Because they’re like you, Alex. Frightened of her. This is her chance to find some purpose in her life. Maybe her only chance. Do you think it helps to have you in constant reaction against her? How do you think it does feel, Alex? How do you think she feels about you wishing she were back on Earth, out of sight and out of mind?

  “You think your job here is solving complicated problems. Spot the hitch, find the answer, Q.E.D., next question, please. Your mission in life is to help make these alien worlds safe for people to live in. To you, that’s very straightforward. But did it ever occur to you that you might have other responsibilities as well? Responsibilities to the other people aboard Daedalus. To Mariel, to Nathan, to Pete? We all have a mission, Alex—in life as well as in our jobs. Do you have to set the kid up as an enemy? Nathan, I may grant you—he can take it. But not the kid.”

  I had to divert the attack. It was too powerful. I just couldn’t sit still and take it.

  “You really do have one hell of a soft core under that hard exterior, don’t you?” I said. I put as much sarcasm into my voice as I could muster.

  It could have made her angry. On another occasion, she might have spit in my eye. But not tonight.

  She had one last thing to say, and she said it straight. “She’s fourteen years old,” she said. “And maybe you don’t feel any sexual tension. But she does.”

  I stayed still. She took her hands away from the heat, rubbed them on her pants, and then stood up.

  “Don’t stay up too late,” she said. “We have an early start to make.”

  Then she went back into the tent.

  CHAPTER NINE

  I didn’t sleep very well. I never do, first night in a strange milieu. The physical discomfort of sleeping on the ground in a crowded tent, together with the mental discomfort of perpetual semi-consciousness, made the remainder of the night unpleasant, and it was a relief to be able to get up with the dawn and prepare to move on. By the end of the second day, I knew, I would have reached a pitch of physical exhaustion which would make it easy to sleep through the second night.

  We ate sparingly of ship’s rations, not wanting to cause delay or discomfort by risking the inconvenient effects of the alien provender. It didn’t take long to get everything packed and to get ourselves back on the march.

  The river grew narrower as it began to wander in long, sinuous curves. By noon we had reached a stretch where it ran considerably faster. But as the river headed down the banks became steeper and the rough trail we followed took us upwards, away from the rippled surface. We could see ahead of us a deep gorge whose sides were steep enough to present the occasional bare face of golden-yellow rock, with only patches of tussock-grass and puny twisted trees scattered here and there. There were rocks projecting out of the water, too, and we could see, far ahead, the foam of rapids.

  We had a choice. Either we could stick close to the river and hope to get through the gorge near water level, or we could start climbing. It had to be the latter. We had no guarantee of being able to get through at the bottom, and the attempt would be far more hazardous than the slower and steeper way. The climb wasn’t something we could look forward to. The warm, humid air was going to make us sweat, and we certainly wouldn’t reach the crown of the gorge in one afternoon’s walk.

  The elevation of the cliff top was much greater than the height of the hill on which the Daedalus had landed, and we could at least look forward to a good view when we did ultimately make it. How useful such a view might be we couldn’t know. In all likelihood it would show us little more than a limitless ocean of leaves.

  The ascent was by no means uniform. There were many ridges and gullies in between our objective and ourselves—far more than our eyes could initially reveal to us. As we walked out the remainder of that day we seemed to come no nearer to the distant target, although we walked aches into our bones, blisters on to our feet, and a creeping tiredness into our every muscle, The miles went by, but they seemed always to be the same miles, over and over again.

  The character of the forest changed subtly as we ascended. The trees grew shorter and tended to assume more complex shapes. The higher we went the more starkly obvious these differences became. The boles of the trees were much thicker, and often gave the impression of being woven out of a number of individual strands bizarrely twisted and plaited together. Root ridges radiated out in all directions, breaking the surface because the soil was shallow and unevenly distributed over the surface of the rock. The limiting factor to the growth of the forest hereabouts was obviously the struggle for water.

  Higher still, adventitious roots which were flattened into solid walls ran along the contour lines of the slope, forming a complex system of water-traps: gutters and dams to take command of the flow of water during heavy rain. Usually, the barricades were complete, running from tree to tree without a break, showing that many of the trees were not, in fact, separate dendritic organisms, but part of the same multiform being. In all probability, many of the tree species typical of the valleys were parts of similar superstructures, united by subterranean roots. How many dendrites might belong to a single genetic and structural entity was open to conjecture. Up here, it seemed that it might be anywhere between two and twelve, but the actual theoretical maximum might have far greater.

  Although there was no question of the entire forest, or even local areas of it, being ‘taken over’ by a single individual, the degree of co-operative interdependence between different plant species here was undoubtedly greater than on Earth. These trees had been together a long, long time. They had grown used to one another’s company, had adjusted to one another’s idiosyncrasy

  If trees have dreams, then this was surely something akin to their Utopia.

  Quite apart from the degree of what might be called the social harmony which existed between the individuals making up the forest there was a tendency for by far the majority of the species to be monoecious—which is say that both male and female reproductive organs were borne on the same plant. Virtually all the flowers were designed for self-fertilization, sometimes insect-aided. Inbreeding was the rule here, not the exception. That made sense. In a highly stable environment the trend must be towards genetic homogeneity, with little heterozygosity in the individual allele-pairs. Inbreeding puts the brake on evolutionary change, preserving stability. Outbreeding, and the wholesale mixing of different genetic complements, is basically an experimental procedure appropriate to meeting the demands of environmental change. It helps preserve the genetic load of recessive lethals and other deleterious mutations. Inbreeding, by constantly pairing up the lethals, weeds the genes out of the population, and maintains the health of the species, so long as environmental constancy can be maintained.

  The same assumptions applied to the birds and butterflies. The striking color-patterns were part of the same system, facilitating mating choice, drawing like to like and helping to preserve and refine genetic consistency. The rich variety of species and the presence of “spectra” of species were testimony to the continual p
rocess of incestual refinement. Species subdivided themselves by accumulating idiosyncrasies—a kind of “binary fission” on the evolutionary scale—and the capacity for variation was thus maintained in the vast range of alternative species rather than (as on Earth) by the variations preserved within the gene pools of individual species.

  Stability inevitably breeds resistance to change.

  That brought me back, as we toiled on up the mountain, to the questions I’d raised earlier about the consequences of invasion. Would the plants taken from the forest flourish under the alien conditions of cultivation which the colonists had tried to impose? There had, of course, been tests—but tests carried out back on Earth, under quarantine conditions. The plants of the forest had shown themselves able to put up with a fairly wide range of stable conditions—but what hadn’t been tested was their ability to stand up over long periods of time—several generations—to conditions which were not stable. On that hillside, where the ships had come down, the colonists, by stripping the land of the trees, had exposed their crops to the wayward whims of weather. That was the danger. Not a considerable climatic change, but a switch from a carefully maintained environment, more akin to a laboratory than a farmer’s field, to an environment of all-but-perpetual changes. Was that, I wondered, one of the problems that had plagued the settlers?

  Even if it was, I decided, it couldn’t be enough. There were still the imported crops to grow in the fields, and the indigenous crops could be gathered from the forest. It cou1dn’t have been by any means an insuperable difficulty.

  There was, of course, the other side of the coin: the possibility that invasion from outside would upset the delicate balance preserved by the forest, and that would set off a great ecological chain reaction and destroy the whole system. But that possibility no longer needed to be considered, because if the Dendran colony had proved nothing else it had at least proved the incompetence of that hypothesis. The forest hadn’t been destroyed by the invasion. It had proved to be immovable. And the colony had obviously been by no means irresistible.

  When we stopped to rest, quite late, our mood reflected our exhaustion.

  “The thing is,” said Karen, “that it doesn’t look a single meter closer now than it did four hours ago.” She was looking up towards the still-distant crown of the gorge.

  “Further away,” said Mariel. She didn’t look as if she could carry on. I felt fairly happy—as if I had a good few miles in me yet. But we had to work on the convoy principle—ask no more of the group than the least is capable of giving.

  “We’re not in any hurry,” I said. “We’ll jack it in, for today.”

  Karen looked at the sun speculatively, measuring the hours of daylight left. But she knew the score. “Sure,” she said. “No point killing ourselves to get to the top. We aren’t climbing it because it’s there. We have to go down the other side, and on to God knows where.”

  I didn’t want to spend too much time on the mountain, if only because we were separated from the river, our primary source of water. But it didn’t really matter that much. There was plenty of moisture to be found in the forest. We wouldn’t go thirsty, even if it didn’t rain for a week. Not too thirsty, anyhow.

  “Suppose you were leaving the settlement,” I mused. “Going elsewhere. As an individual, or as a group. Abandoning what the colony had already achieved and looking for a new start. You might set off following the river. But would you climb the mountain? Or would you pick easier ground and go around?”

  They both eyed the crest of the ridge, high up in the clouds, and considered the question.

  “Climb it,” said Mariel.

  Karen nodded agreement. “Every time,” she said. “It’s damn near due north, toward the sun. They knew that there’s a vast plain on the other side, and a lake. If they were leaving their lives behind, they wouldn’t make it easy on themselves. They’d go up and over. And on.”

  I agreed, too. Intuition, or a feeling for human nature, either way I thought that we were right.

  “You think some of them did leave the settlement and go elsewhere?” asked Karen, turning back to look at me. I didn’t know. But I nodded.

  “Why?”

  I shrugged slightly. “Because of the forest,” I said.

  “What’s that supposed to mean?”

  “It’s beautiful,” I said, simply. “A damn sight more beautiful than that bare hillside. You’d have to build a wall round a place like that to keep me in.”

  Our eyes met, very briefly. She knew what I meant.

  We began to unpack, and to pitch the tent. It didn’t take long, and it left us with a lot of time on our hands—hours of daylight and nothing to do. Mariel was content to lie down and take the strain off her ligaments, but I still had energy in me that wouldn’t let me flop like a rag doll no matter how tired my legs were. I wandered off along the slope, toward the edge of the shallow cliff which fell away to the river. I looked over and down. It was a long way, but I didn’t find the sight particularly vertiginous. The slope wasn’t sheer enough to carry me all the way down even if I did fall. It was safe enough, although there was a good deal of loose stone and soil around.

  I found somewhere solid to sit down—a coign of vantage from which I commanded a view of the whole great valley. I scanned the far slope with my eyes, carefully. There was so much of it that my eyes tried to take in too much at once, but I managed to narrow the focus of my attention.

  There was a small herd of mammalian creatures grazing among the green patches that formed a mosaic against the yellow rocks of the lower part of the face. They were too far away to see clearly. I had to get up and go back for the binoculars.

  “Come and look,” I said to Karen.

  “What at?”

  “Mountain goats.”

  Another time, she would have laughed, but she had nothing better to do. She came to look at the mountain goats. Surprisingly, after a moment’s hesitation, Mariel got up and followed us.

  The creatures weren’t, in fact, much like goats. They looked more like hairy whippets, no more than a meter from nose to tail. There were about thirty in the herd. It was the first sizable group of flightless warm-blooded animals that we’d seen. The mammals were the least obtrusive of all the forest-dwellers.

  “Lords of the world,” I commented, when I passed on the glasses. “The pinnacle of evolution.”

  “What about the monkeys?” asked Karen, who had rather narrow anthropomorphic loyalties.

  “Close relatives,” I said. “Smallish, dog-like general-purpose bodies. The monkeys are modified for dancing about in the treetops, these for dancing about on the ridges. But they’re cousins. ‘Monkey’ is only a convenience-term—it doesn’t imply any kinship, even by analogy, with the human animal. There are no upright mammals with big brains here. If there are any animals with big brains it will be ones that live in the sea. The forest-dwellers are pretty standardized. The predators aren’t too different from those things. Even the largest herbivores look like pigs or giant mice. A lot of them still have scales as well as hair, and there’s a degree of continuity with the browsing lizards, just as there is between the lizards and the frogs. There’s no powerful selection encouraging adaptive radiation, you see. Everything on Dendra is the standard economy model. A slow evolutionary diffusion. Even the birds, apart from their plumage, are physically very standardized. Only the insects, probably with the help of a few million years start, have managed to explore a great many evolutionary avenues.”

  “I bet the dinosaurs never died out either,” she murmured, taking the lecture philosophically.

  “No,” I said. “They never evolved....”

  “Don’t bother to explain why,” she said, quickly. “I’ll guess. It’ll be more fun.”

  I shut up, feeling slightly unappreciated.

  Mariel, meanwhile, had tired of the goats and was scanning the distant slopes with the binoculars in the hope of picking up something new. As she swung the lenses round to their limit, lo
oking forward along the course of the river to a green area just visible beyond the gorge, through the narrow crack between the two faces of rock, she stopped.

  “Smoke!” she said, in surprise.

  I looked where the glasses were pointing. I couldn’t see a thing. It was much too far.

  “Can’t be,” I said. “The trees won’t burn.” But even as I said it I was aware of the catch. The trees didn’t burn—unless the outer coating was stripped away and the xylem chopped up to make firewood...

  She pointed, handing me the glasses. “It’s smoke,” she said.

  I looked. Even through the glasses the green blur of the, land beyond the gorge didn’t seem any clearer. I could see the grayish haze which Mariel had identified as smoke, but it was so tenuous...

  I altered the focus of the glasses, very slightly, and realized that the gray haze and the green blur weren’t equidistant. The haze was, in fact, rather closer—in the gorge, above the surface of the river. It was a swirling cloud, drifting close to a patch of scrub clinging to a crevice above the rushing water. It seemed to sparkle, to change as it swirled. It was a kind of yellow-gray, but it didn’t look like wood smoke to me. And there was definitely no hint of flame. While it isn’t always true that there’s no smoke without fire, the absence of the latter is at least grounds for suspicion...

  The cloud wasn’t smoke. It wasn’t ascending into the sky, just swirling round and round. It wasn’t at the mercy of the wind, which must have been quite tangible in the crack of the gorge. How big it might be I couldn’t really tell, because it was too far away, but it must have been quite some size, involving millions of individual particles.

  “They’re butterflies,” I declared. “It’s a cloud of insects. The sparkle effect is the fluttering of parti-colored wings. Yellow and white—maybe yellow and blue. There are millions of them.”