The Gentle Giants of Ganymede

be modified into developing a mechanism for dealing with carbon dioxide that did not depend on its secondary system. We have evidence that they achieved the first two of these objectives; the third must necessarily remain speculative, at least for the time being.'

'And if they did succeed in the third, then the next step would be. . .' Hunt #146;s voice trailed off again. The sheer ingenuity of the Ganymean scheme made it difficult for him to accept it unquestioningly.

'If it worked, and if there were no undesirable side effects, the intention was no doubt to engineer the same codes into themselves,' Danchekker confirmed. 'Thus they would enjoy an in-built tolerance that would happily continue to perpetuate itself through succeeding generations, while at the same time preserving all the advantages that they had already gained by doing away with their secondary systems. A fascinating example of what intelligence can do to improve on Nature when natural evolution throws up a solution that leaves much to be desired, don #146;t you think?'

Hunt rose from his chair and began pacing slowly from one side of the office to the other as he marveled at the sheer audacity of even conceiving such a scheme. The Ganymeans had expressed wonder at Man #146;s readiness to meet Nature head-on in every challenge, but here was something, surely, that Man would have balked at. The basic instincts of the Ganymeans steered them away from physical danger, conflict and the like, but their thirst for intellectual adventure and combat, it appeared, was unquenchable; that was the spur that had driven them to the stars. Danchekker watched in silence, waiting for the question that he knew would come next. At length Hunt stopped and wheeled to face the desk.

'Yes, it was neat, all right,' he agreed. 'But it didn #146;t work, did it, Chris?'

'Regrettably, no,' Danchekker conceded. 'But not for reasons for which, I feel, they were really to blame. We might have some catching up to do with them technically, but nevertheless I believe that we are in a position to see where they went wrong.' He didn #146;t wait for the obvious question at that point but went on. 'We have the advantage of knowing far more than they possibly could have about life on our own planet. We have access to the work of thousands of scientists who have studied the subject for centuries, but the Ganymeans who came here twenty-five million years ago did not. In particular, they could not have known what Professor Tatham and his team at Cambridge have only just discovered.'

'The scrambling together of the self-immunization and the CO2 -tolerance codings?'

'Yes, exactly that. The thing that the Ganymean genetic engineers would never have realized was that in isolating the latter, in order to make their proposed later experiments simpler, they were losing the former. Because of the method they adopted, the descendant strains that they bred would have been ideal subjects for further C02 -tolerance research, but they would also have lost their self-immunization capabilities. In other words, the Ganymeans created and raised a whole range of mixed terrestrial animal species that possessed no trace of the age-old mechanism for stimulating their own defensive processes by flooding the body with mild doses of pollutants #151;a mechanism which we still see today in the descendants of the animals that remained on Earth to continue evolving naturally, of course.'

Hunt had stopped pacing and was now looking down at Danchekker with a slow frown spreading across his face, as if another thought had just struck him.

'But there #146;s something else, isn #146;t there?' he said. 'The self-immunization process has something to do with higher brain functions. . . . Are you saying what I think you #146;re saying?'

'I suspect so. As you know, the toxins introduced into the body by the self-immunization process in today #146;s animals has the effect of inhibiting the development of the higher brain centers. And another thing #151;Tatham #146;s latest work indicates that, because of the way terrestrial life happens to have evolved, the capacity for violence and aggression is closely related to the development of those centers too. Thus, the Ganymeans would have found themselves unable to produce variants of the type they wanted without also removing the inhibition on the development of higher brain functions, and in addition producing an enhanced tendency toward aggression. That being the case and the Ganymeans being the way they were, I can #146;t really see them taking the experiment any further. They would never have risked introducing anything like that into themselves, whatever the urgency of the situation. Never.'

'So they gave the whole thing up as a bad job in the end and went off to pastures new,' Hunt completed.

'Maybe, and again maybe not. We have no way of telling for sure. I certainly hope so for the sake of Garuth and his friends.' Danchekker leaned forward on the desk and at once his mood became more serious. 'But whatever the answer to that is, at least we have a definite answer to another of the questions that you asked at the beginning.'

'Which one?'

'Well, consider the situation that must have existed on Minerva when the Ganymeans came to the point of accepting that their ambitious genetic engineering solution was running into trouble. They could go away to another star or stay on their own world and perish. Either way, the days of the Ganymean presence on Minerva were numbered. Now take them out of the equation, and what is left? Answer #151;two populations of animals both of which are well adapted to handling the environmental conditions. First there are the native Minervan types, and second the artificially mutated descendants of the imported terrestrial types, free to roam the planet after the departure of the Ganymeans. Now return to the equation one further factor that I have established through long interrogation of ZORAC #146;s archives #151;the native Minervan species would not have been poisonous to terrestrial carnivores #151;and what do you conclude?'

Hunt gazed back with eyes that were suddenly aghast.

'Christ!' he breathed. 'It would have been a bloody slaughter.'

'Yes, indeed. Consider a planet inhabited only by those ridiculous Technicolored cartoon animals that we found drawn on the walls of that ship at Pithead #151;animals that had never evolved any specializations for defense, concealment or escape, and which had no need for fight-or-flight instincts at all. Now throw in among them a typical mix of predators from Earth #151;every one a selected product of millions of years of improvement of the arts of ferocity, stealth and cunning. . . added to which they were evolving higher levels of intelligence that had previously been inhibited and their already fearsome aggressiveness was being further reinforced. Now what picture do you see?'

Hunt just continued to stare in horrified silence as the picture unfolded before his mind #146;s eye.

'That #146;s what wiped them all out,' he said at last. 'That poor bloody Minervan zoo wouldn #146;t have had a chance. No wonder it didn #146;t last for more than a few generations after the Ganymeans disappeared from the scene.'

'With another consequence as well,' Danchekker came in. 'The terrestrial carnivores concentrated on the most readily available prey #151;the native species #151;and so gave the terrestrial herbivores a breathing space to increase their numbers and become firmly established. By the time the Minervan natives had been wiped out the carnivores would have been forced to revert to their old habits, but by that time the situation would have stabilized. A mixed and balanced terrestrial animal ecology had been given time to establish itself across Minerva. . . .' The professor #146;s voice took on a soft and curious tone. 'And that is the way things must have remained . . . right on through until the time of the Lunarians.'

'Charlie. . .' Hunt sensed that Danchekker was at last hinting at something he had been building up to all along. 'Charlie,' Hunt repeated. 'You found that same enzyme in him too, didn #146;t you?'

#145;We did, but in a somewhat degenerate form. . . as if it were in the last phases of fading away completely. It did fade away of course, since Man no longer possesses it. . . . But the interesting point, as you say, is that Charlie had it and so, presumably, did the rest of the Lunarians.'

'And there was only one place for it to come from. . .'

'Precisely.'

Hunt raised a hand to his brow as the full import of these revelations hit him. He turned slowly to meet Danchekker #146;s solemn gaze and then slowly, his features knotted into a mask of disbelief that strove to reject the things that reason now stripped bare, sank weakly down onto an arm of the nearest chair. Danchekker said nothing, waiting for Hunt to put the pieces together for himself.

'The population on Minerva included samples of the latest Oligocene primates,' Hunt said after a while. 'They were almost certainly as advanced as anything that Earth had produced at the time, and with the greatest potential for advancing further. The Ganymeans had unwittingly removed the inhibition on further brain development. . . .' He looked up and met Danchekker #146;s imperturbable stare again. 'They #146;d have raced ahead from there.