"Ah, but you're missing the whole point," Danchekker interrupted. "Those were new strains, true, but they fell neatly into the known standard families. They exhibited characteristics that place them firmly and definitely within known related groups." He gestured again toward the screen. "That one doesn't. It's completely new. To me it suggests a whole new class of its own--a class that contains just one member. Nothing yet identified in the metabolism of any form of life as we know it has ever done that before." Danchekker swept his eyes around the small circle of faces.
"Every species of animal life that we know belongs to a known family group and has related species and ancestors that we can identify. At the microscopic level the same thing applies. All our previous experiences tell us that even if this enzyme does date from twenty-five million years back, we ought to be able to recognize its family characteristics and relate it to known enzyme strains that exist today. However, we cannot. To me this indicates something very unusual."
Wolfgang Fichter, one of Danchekker's senior biologists, rubbed his chin and stared dubiously at the screen. "I agree that it is highly improbable, Chris," he said. "But can you really be so sure that it is impossible? After all, over twenty-five million years? . . . Environmental factors may have changed and caused the enzyme to mutate into something unrecognizable. I don't know, some change in diet maybe . . . something like that."
Danchekker shook his head decisively. "No. I say it's impossible." He raised his hands and proceeded to count points off on his fingers. "One--even if it did mutate, we'd still be able to identify its basic family architecture in the same way we can identify the fundamental properties of, say, any vertebrate. We can't.
"Two--if it occurred only in one species of Oligocene animal, then I would be prepared to concede that perhaps the enzyme we see here had mutated and given rise to many strains that we find in the world today--in other words this strain represents an ancestral form common to a whole modern family. If such were the case, then perhaps I'd agree that a mutation could have occurred that was so severe that the relationship between the ancestral strain and its descendants has been obscured. But that is not the case. This same enzyme is found in many different and nonrelated Oligocene species. For your suggestion to apply, the same improbable process would have had to occur many times over, independently, and all at the same time. I say that's impossible."
"But. . ." Carpenter began, but Danchekker pressed on.
"Three--none of today's animals possesses such an enzyme in its microchemistry yet they all manage perfectly well without it. Many of them are direct descendants of Oligocene types from the Ganymean ship. Now some of those chains of descent have involved rapid mutation and adaptation to meet changing diets and environments while others have not. In several cases the evolution from Oligocene ancestors to today's forms has been very slow and has produced only a small degree of change. We have made detailed comparisons between the microchemical processes of such ancestral Oligocene ancestors recovered from the ship and known data relating to animals that exist today and are descended from those same ancestors. The results have been very much as we expected--no great changes and clearly identifiable relationships between one group and the other. Every function that appeared in the microchemistry of the ancestor could be easily recognized, sometimes with slight modifications, in the descendants." Danchekker shot a quick glance at Fichter. "Twenty-five million years isn't really so long on an evolutionary time scale."
When no one seemed ready to object, Danchekker forged ahead. "But in every case there was one exception--this enzyme. Everything tells us that if this enzyme were present in the ancestor, then it, or something very like it, should be readily observable in the descendants. Yet in every case the results have been negative. I say that cannot happen, and yet it has happened."
A brief silence descended while the group digested Danchekker's words. At length Sandy Holmes ventured a thought. "Couldn't it still be a radical mutation, but the other way around?"
Danchekker frowned at her.
"How do you mean, the other way around?" asked Henri Rousson, another senior biologist, seated next to Carpenter.
"Well," she replied, "all the animals on the ship had been to Minerva, hadn't they? Most likely they were born there from ancestors the Ganymeans had transported from Earth. Couldn't something in the Minervan environment have caused a mutation that resulted in this enzyme? At least that would explain why none of today's terrestrial animals have it. They've never been to Minerva and neither have any of the ancestors they've descended from."
"Same problem," Fichter muttered, shaking his head.
"What problem?" she asked.
"The fact that the same enzyme was found in many different and nonrelated Oligocene species," Danchekker said. "Yes, I'll grant that differences in the Minervan environment could mutate some strain of enzyme brought in from Earth into something like that." He pointed at the screen again. "But many different species were brought in from Earth--different species each with its own characteristic metabolism and particular groups of enzyme strains. Now suppose that something in the Minervan environment caused those enzymes--different enzymes--to mutate. Are you seriously suggesting that they would all mutate independently into the same end-product?" He waited for a second. "Because that is exactly the situation that confronts us. The Ganymean ship contained many preserved specimens of different species, but every one of those species possessed precisely the same enzyme. Now do you want to reconsider your suggestion?"
The woman looked helplessly at the table for a second, then made a gesture of resignation. "Okay. . . If you put it like that, I guess it doesn't make sense."
"Thank you," Danchekker acknowledged stonily.
Henri Rousson leaned forward and poured himself a glass of water from the pitcher standing in the center of the table. He took a long drink while the others continued to stare thoughtfully through the walls or at the ceiling.
"Let's go back to basics for a second and see if that gets us anywhere," he said.'We know that the Ganymeans evolved on Minerva--right?" The heads around him nodded in assent. "We also know that the Ganymeans must have visited Earth because there's no other way they could have ended up with terrestrial animals on board their ship--unless we're going to invent another hypothetical alien race and I'm sure not going to do that because there's no reason to. Also, we know that the ship found here on Ganymede had come to Ganymede from Minerva, not directly from Earth. If the ship came from Minerva, the terrestrial animals must have come from Minerva too. That supports the idea we've already got that the Ganymeans were shipping all kinds of life forms from Earth to Minerva for some reason."
Paul Carpenter held up a hand. "Hang on a second. How do we know that the ship downstairs came here from Minerva?"
"The plants," Fichter reminded him.
"Oh yeah, the plants. I forgot. . ." Carpenter subsided into silence.
The pens and animal cages in the Ganymean ship had contained vegetable feed and floor-covering materials that had remained perfectly preserved under the ice coating formed when the ship's atmosphere froze and the moisture condensed out. Using seeds recovered from this material, Danchekker had succeeded in cultivating live plants completely different from anything that had ever grown on Earth, presumed to be examples of native Minervan botany. The leaves were very dark--almost black--and absorbed every available scrap of sunlight, right across the visible spectrum. This seemed to tie in nicely with independently obtained evidence of Minerva's great distance from the Sun.
"How far," Rousson asked, "have we got in figuring out why the Ganymeans were shipping all the animals in?" He spread his arms wide. "There had to be a reason. How far are we getting on that one? I don't know, but the enzyme might have something to do with it."
"Very well, let's recapitulate briefly what we think we already know about the subject," Danchekker suggested. He moved away from the screen and perched on the edge of the table. "Paul. Would you like to tell us your answer to Henr
i's question." Carpenter scratched the back of his head for a second and screwed up his face.
"Well . . ." he began, "first there's the fish. They're established as being native Minervan and give us our link between Minerva and the Ganymeans."
"Good," Danchekker nodded, mellowing somewhat from his earlier crotchety mood. "Go on."
Carpenter was referring to a type of well-preserved canned fish that had been positively traced back to its origin in the oceans of Minerva. Danchekker had shown that the skeletons of the fish correlated in general arrangement to the skeletal remains of the Ganymean occupants of the ship that lay under the ice deep below Pithead Base; the relationship was comparable to that existing between the architectures of, say, a man and a mammoth, and demonstrated that the fish and the Ganymeans belonged to the same evolutionary family. Thus if the fish were native to Minerva, the Ganymeans were, too.
"Your computer analysis of the fundamental cell chemistry of the fish," Carpenter continued, "suggests an inherent low tolerance to a group of toxins that includes carbon dioxide. I think you also postulated that this basic chemistry could have been inherited from way back in the ancestral line of the fish--right from very early on in Minervan history."
"Quite so," Danchekker approved. "What else?"
Carpenter hesitated. "So Minervan land-dwelling species would have had a low CO2 tolerance as well," he offered.
"Not quite," Danchekker answered. "You've left out the connecting link to that conclusion. Anybody. . . ? " He looked at the German. "Wolfgang?"
"You need to make the assumption that the characteristics of low CO2 tolerance came about in a very remote ancestor--one that existed before any land-dwelling types appeared on Minerva." Fichter paused, then continued. "Then you can postulate that this remote life form was a common ancestor to all later land dwellers and marine descendants--for example, the fish. On the basis of that assumption you can say that the characteristic could have been inherited by all the land-dwelling species that emerged later."
"Never forget your assumptions," Danchekker urged. "Many of the problems in the history of science have stemmed from that simple error. Note one other thing too: If the low-C02 -tolerance characteristic did indeed come about very early in the process of Minervan evolution and survived right down to the time that the fish was alive, then suggestions are that it was a very stable characteristic, if our knowledge of terrestrial evolution is anything to go by anyway. This adds plausibility to the suggestion that it could have become a common characteristic that spread throughout all the land dwellers as they evolved and diverged, and has remained essentially unaltered down through the ages--much as the basic design of terrestrial vertebrates has remained unchanged for hundreds of millions of years despite superficial differences in shape, size and form." Danchekker removed his spectacles and began polishing the lenses with his handkerchief.
"Very well," he said. "Let us pursue the assumption and conclude that by the time the Ganymeans had evolved--twenty-five million years ago--the land surface of Minerva was populated by a multitude of its own native life forms, each of which possessed a low tolerance to carbon dioxide, among other things. What other clues do we have available to us that might help determine what was happening on Minerva at that time?"
"We know that the Ganymeans were quitting the planet and trying to migrate someplace else," Sandy Holmes threw in. "Probably to some other star system."
"Oh, really?" Danchekker smiled, showing his teeth briefly before breathing on his spectacle lenses once more. "How do we know that?"
"Well, there's the ship down under the ice here for a start," she replied. "The kind of freight it was carrying and the amount of it sure suggested a colony ship intending a one-way trip. And then, why should it show up on Ganymede of all places? It couldn't have been traveling between any of the inner planets, could it?"
"But there's nothing outside Minerva's orbit to colonize," Carpenter chipped in. "Not until you get to the stars, that is."
"Exactly so," Danchekker said soberly, directing his words at the woman. "You said'suggested a colony ship.' Don't forget that that is precisely what the evidence we have at present amounts to--a suggestion and nothing more. It doesn't prove anything. Lots of people around the base are saying we now know that the Ganymeans abandoned the Solar System to find a new home elsewhere because the carbon-dioxide concentration in the Minervan atmosphere was increasing for some reason which we have yet to determine. It is true that if what we have just said was fact, then the Ganymeans would have shared the low tolerance possessed by all land dwellers there, and any increase in the atmospheric concentration could have caused them serious problems. But as we have just seen, we know nothing of the kind; we merely observe one or two suggestions that might add up to such an explanation." The professor paused, seeing that Carpenter was about to say something.
"There was more to it than that though, wasn't there?" Carpenter queried. "We're pretty certain that all species of Minervan land dwellers died out pretty rapidly somewhere around twenty-five million years ago . . . all except the Ganymeans themselves maybe. That sounds like just the effect you'd expect if the concentration did rise and all the species there couldn't handle it. It seems to support the hypothesis pretty well."
"I think Paul's got a point," Sandy Holmes chimed in. "Everything adds up. Also, it fits in with the ideas we've been having about why the Ganymeans were shipping all the animals into Minerva." She turned toward Carpenter, as if inviting him to complete the story from there.
As usual, Carpenter didn't need much encouragement. "What the Ganymeans were really trying to do was redress the CO2 imbalance by covering the planet with carbon-dioxide-absorbing, oxygen-producing terrestrial green plants. The animals were brought along to provide a balanced ecology that the plants could survive in. Like Sandy says, it all fits."
"You're trying to fit the evidence to suit the answers that you already want to prove," Danchekker cautioned. "Let's separate once more the evidence that is fact from the evidence which is supposition or mere suggestion." The discussion continued with Danchekker leading an examination of the principles of scientific deduction and the techniques of logical analysis. Throughout, the figure who had been following the proceedings silently from his seat at the end of the table farthest from the screen continued to draw leisurely on his cigarette, taking in every detail.
Dr. Victor Hunt had also accompanied the team of scientists who had come with Jupiter Five more than three months before to study the Ganymean ship. Although nothing truly spectacular had emerged during this time, huge volumes of data on the structure, design and contents of the alien ship had been amassed. Every day, newly removed devices and machinery were examined in the laboratories of the surface bases and in the orbiting J4 and J5 mission command ships. Findings from these tests were as yet fragmentary, but clues were beginning to emerge from which a meaningful picture of the Ganymean civilization and the mysterious events of twenty-five million years before might eventually emerge.
That was Hunt's job. Originally a theoretical physicist specializing in mathematical nucleonics, he had been brought into the UN Space Arm from England to head a small group of UNSA scientists; the group's task was to correlate the findings of the specialists working on the project both on and around Ganymede and back on Earth. The specialists painted the pieces of the puzzle; Hunt's group fitted them together. This arrangement was devised by Hunt's immediate boss, Gregg Caldwell, executive director of the Navigation and Communications Division of UNSA, headquartered in Houston. The scheme had already worked well in enabling them to unravel successfully the existence and fate of Minerva, and first signs were that it promised to work well again.
He listened while the debate between the biologists went full circle to end up focusing on the unfamiliar enzyme that had started the whole thing off.
"No, I'm afraid not," Danchekker said in reply to a question from Rousson. "We have no idea at present what its purpose was. Certain functions in its reaction e
quations suggest that it could have contributed to the modification or breaking down of some kind of protein molecule, but precisely what molecule or for what purpose we don't know." Danchekker gazed around the room to invite further comment but nobody appeared to have anything to say. The room became quiet. A mild hum from a nearby generator became noticeable for the first time. At length Hunt stubbed his cigarette and sat back to rest his elbows on the arms of his chair. "Sounds as if there's a problem there, all right," he commented. "Enzymes aren't my line. I'm going to have to leave this one completely to you people."
"Ah , nice to see you're still with us, Vic," Danchekker said, raising his eyes to take in the far end of the table. "You haven't said a word since we sat down."
"Listening and learning." Hunt grinned. "Didn't have a lot to contribute."
"That sounds like a philosophical approach to life," Fichter said, shuffling the papers in front of him. "Do you have many philosophies of life. . . maybe a little red book full of them like that Chinese gentleman back in nineteen whatever it was?"
"'Fraid not. Doesn't do to have too many philosophies about anything. You always end up contradicting yourself. Blows your credibility."
Fichter smiled. "You've nothing to say to throw any light on our problem with this wretched enzyme then," he said.
Hunt did not reply immediately but pursed his lips and inclined his head to one side in the manner of somebody with doubts about the advisability of revealing something that he knew. "Well," he finally said, "you've got enough to worry about with that enzyme as things are." The tone was mildly playful, but irresistibly provocative. All heads in the room swung around abruptly to face in his direction.
"Vic, you're holding out on us," Sandy declared. "Give."
Danchekker fixed Hunt with a silent, challenging stare. Hunt nodded and reached down with one hand to operate the keyboard recessed into the edge of the table opposite his chair. Above the far side of Ganymede, computers on board Jupiter Five responded to his request. The display on the conference room wall changed to reveal a densely packed columnar arrangement of numbers.
The Gentle Giants of Ganymede g-2 Page 2
