PART ONE
THE VISIT
There was a time, half a million years ago or so, when some new neighbors came into the vicinity of the Earth's 'solar system. They were eager to be friendly—that is, that was what they wanted to be, if they could find anyone around to be friends with. So one day they dropped in on the third planet of the system, the one we now know as Earth itself, to see who might be at home.
It wasn't a good time to pay a call. Oh, there was plenty of life on Earth, no doubt of that. The planet crawled with the stuff. There were cave bears and saber-tooth cats and things like elephants and things like deer. There were snakes and fish and birds and crocodiles; and there were disease germs and scavengers; and there were forests and savannahs and vegetation of all kinds. But one element was conspicuously missing in the catalogue of terrestrial living creatures. That was a great pity, because that was the one quality the visitors were most anxious to find.
What those visitors from space couldn't find anywhere on the planet was intelligence. It just hadn't been invented yet.
The visitors sought it very diligently. The closest they could find to a being with what they were after was a furry little creature without language, fire, or social institutions—but which did, at least, have a few promising skills. (For instance, it could manage to crunch tools out of random bits of rock.) When modern humans came along and began tracing their evolutionary roots they would name this particular brand of prehuman "Australopithecus." The visitors didn't call it anything in particular . . . except one more disappointment in their quest for civilized company in space.
The little animals weren't very tall—about the size of a modern six-year-old—but the visitors didn't hold that against them. They had no modern humans to compare the little guys with, and anyway they weren't terribly tall themselves.
This was the chancy Pleistocene, the time when the ice was growing and retreating in Europe and North America, when African rainfall patterns swelled and diminished, and adaptability was the key for any species that wanted to stay alive. At the time the visitors arrived, the countryside in which they found a tribe of their little pets was rolling, arid savannah, covered with grasses and occasional wildflowers. Where the australopithecines had camped was in a meadow by the banks of a slow, trickly little stream that flowed into a huge salty lake a few kilometers away. On the western horizon a line of mountains stretched away out of sight. The nearest of them steamed gently. The mountains were all volcanoes, though of course the australopithecines did not have any idea what a volcano was. They did have fire, to be sure; they'd gotten that far in technological sophistication. At least, most of the time they did, when lightning started grass burning (or even when hot ash from an eruption kindled something near them, though fortunately for the peace of mind of the little people that didn't happen often). They didn't use fire for much. They had not yet considered the possibility of cooking with it, for instance. What they found it good for was keeping large nocturnal predators away, at which it sometimes succeeded.
By day they could take pretty good care of themselves. They carried stone "hand axes"—not very elaborate, just rocks chipped into more or less the shape of a fat, sharp-edged clam—and clubs that were even less impressive looking: just the unmodified long leg bones of the deer-like grazers they liked to eat. That sort of weapon would never stop a saber-tooth. But enough of them, wielded by enough of the screaming little ape-men, could usually deter the hyenas that were the savannah's fiercest predators, especially if the little folk had first discouraged the hyena pack by pelting it with rocks from a distance. They didn't usually succeed in killing the hyenas, but most of the time they did convince the animals that their time would be better spent on more defenseless prey.
The little people did lose a baby to a carnivore now and then, of course, or an old person whose worn-out teeth were making his or her life chancy anyway. They could stand that. They seldom lost anyone important to the well-being of the tribe—except when hunting, of course. But they didn't have any choice about taking the risks of the hunt. They had to hunt to eat.
Although the australopithecines were tiny, they were quite strong. They tended to have pot bellies, but the gluteus maximus was quite small—even the females had no hips to speak of. Their faces were not very human: no chin worth mentioning, a broad nose, tiny ears almost hidden in the head fur—you wouldn't call it hair yet. An average australopithecine's skull did not have room for any large supply of brains. If you poured the brains out of his sloped skull into a pint beer mug, they would probably spill over the edge, but not much.
Of course, no modern beer drinker would do that, but one of the little furry people might have—gladly. In their diet, brains were a delicacy. Even each other's.
The visitors didn't think much of the furry people's eating habits. Still, the creatures had one anatomical characteristic that interested the visitors a lot—in a sort of winky-jokey way, with sexual overtones. Like the visitors, the australopithecines were bipeds. Unlike the visitors, their legs were positioned so close to each other that they actually rubbed together at the thighs when they walked—and for the males, at least, that seemed to the visitors to present real problems, since the male sexual organs hung between the thighs.
(Some hundreds of thousands of years later, the then paramount denizens of Earth, the human race, would ask themselves similar questions about the long-gone visitors . . . and they, too, would fail to understand.)
So the visitors from space looked the little furry creatures over for a while, then chirruped their disappointment to each other, got back in their spaceships, and went glumly away.
Their visit had not been a total loss. Any planet that bore life at all was a rare jewel in the galaxy. Still, they had really been hoping for a more sophisticated kind of life—someone to meet and be friends and interchange views and have discussions with. These little furry animals definitely weren't up to any of that. The visitors didn't leave them quite untouched, though. The visitors had learned, from dismal experience, that faintly promising species of creatures might easily die off, or take a wrong turning somewhere along the evolutionary line, and so never realize their promise. So the visitors had a policy of establishing a sort of, well, call them "game preserves." Accordingly, they took a few of the australopithecines away with them in their spaceships when they left. They put the little beasts in a safe place, in the hope that they might amount to something after all. Then the visitors departed.
Time passed . . . a lot of time.
The australopithecines never did get very far on Earth. But then their close relatives—the genus Homo, better known as you and me and all our friends—came along. The genus Homo people worked out a lot better. Over some five hundred thousand years, in fact, they did just about all the things the visitors had hoped for from the australopithecines.
These "humans," as they called themselves, were pretty clever at thinking things up. As the ages passed they invented a lot of neat stuff—the wheel, and agriculture, and draft animals, and cities, and levers and sailing ships and the internal combustion engine and credit cards and radar and spacecraft. They didn't invent them all at once, of course. And not everything they invented turned out to be an absolute boon, because along the way they also invented clubs and swords and bows and catapults and cannon and nuclear missiles. These humans had a real talent for messing things up.
For instance, a lot of their inventions were the kind that looked as though they ought to do something, but really did something very different—which was the case with all their "peacekeeping" gadgets, none of which kept any peace. "Medicine" was another case in point. They invented what they called medicine quite early—that is, they invented the practice of doing all sorts of bizarre things to people who were unfortunate enough to get sick. Ostensibly the things they did were intended to make the sick person better; often enough they went the other way. At best, they generally didn't help. The man who was dying of malaria may have been grateful to his local doctor for putting on the devil mask and dancing around the bed, but the patient died anyway. By the time human medicine reached the point where a sick person's chances of recovery were better with a doctor than without one—that took about 499,900 of those 500,000 years—humans had managed to find a more efficient way of screwing things up. They had invented money. Human medicine became fairly good at curing many human ailments, but more and more of the human race began to have trouble finding the money to pay for it.
And along about the same time, the humans who lived on this little green planet called Earth finally reached the point where they could get off it for the first time. The age of human exploration of space had begun.
In a sense, this was a happy coincidence. By the time human beings reached the point of being able to launch a spaceship, it may well have been true that it was also getting to be a good time to think seriously about leaving the Earth, for good. The Earth was a pretty good place to be rich in. It was a very bad one to be poor in.
By then, of course, the people who had dropped in on the australopithecines were long gone.
In their yearning quest for some other intelligent race to talk to they had surveyed more than half the galaxy. Actually, there were some successes, or almost successes. They did find a few promising species—well, at least as promising as the poor, dumb australopithecines. Probably the race that came closest to what they were looking for were the ones they called the Slow Swimmers. These people (no, they didn't look a bit like "people," but in fairness that was more or less what they were) lived in the dense liquid-gas atmosphere of a heavy planet. The Slow Swimmers had language, at least. In fact, they sang beautiful, endless songs in their language, which the visitors finally managed to puzzle out enough to understand. The Slow Swimmers even had cities—sort of cities—well, what they had was domiciles and public structures that floated around in the soupy mud they lived in. The Slow Swimmers weren't a lot of fun to talk to, but the main reason for that was that they were, you'd better believe it, really slow. If you tried to talk to them you had to wait a week for them to get out a word, a year to finish the first few bars of one of their songs—and a couple of lifetimes, anyway, to carry on a real conversation. That wasn't the Slow Swimmers' fault. They lived at such a low temperature that everything they did was orders of magnitude slower than warm-blooded oxygen-breathers like human beings—or like the visitors from space.
Then the visitors found someone else . . . and that was a whole other thing, and a very scary one. They stopped looking after that.
When human beings went into space they had their own agenda, which wasn't quite the same as the purposes of their ancient visitors. The humans weren't really looking for other intelligences, at least not in the same way. The human telescopes and probe rockets had told them long ago that no intelligent aliens were going to be found, at least in their own solar system—and they had little hope of going any farther than that.
The humans might well have looked for their long-ago visitors if they had had any idea they existed. But, of course, they didn't.
Maybe the best way to find another intelligent race is to be lucky rather than purposeful. When human beings got to the planet Venus it didn't look very promising. The first humans to look at it didn't "look"—no one could see very far through its miserably dense and murky air—they just circled around it in orbit, feeling for surface features with radar. What they found wasn't encouraging. Certainly when the first human rockets landed beside the Rift Valley of Aphrodite Terra and the first parties began to explore the inhospitable surface of Venus they had no hope of finding life there.
And, sure enough, they didn't. But then, in a part of Venus called Aino Planitia, a geologist made a discovery. There was a fissure—call it a tunnel, though at first they thought it might be a lava tube—under the surface of the planet. It was long, it was regular . . . and it had no business being there.
The Venusian explorers, without warning, had found the first signs of that half-million-year-ago visit . . .