Dinotherium became moderately alarmed, and ceased browsing. These gesticulating bipeds could hardly harm him, but their proximity and persistence were unnatural. He ran smoothly, desiring only to free himself of the strange situation so he could finish his browse. He bore left, away from the concentration of Australopithecines.
Suddenly he realized where he was. Ahead was a deep sharp gully, the product of seasonal flash floods, whose tumbling sides were treacherous for a creature of his size. He veered farther left—and encountered more men.
The choice was between the gully and the men, now that he was fleeing. The gully at least was a known danger. But—there was a gap in the line, an easy escape. Dinotherium charged at it.
The noise increased. Men ran to cut him off, chattering. But the nearest one stood indecisively, failing to act in time. Dinotherium plunged through the space and headed for the swamp where men would be foolish to follow.
"He got away," Mrs. Rhodes said, relieved.
"Because one man did not follow instructions," Miss Concher said. "The leader plainly hooted at the fool to close it up, but he didn't comprehend in time."
"Yes, I saw that. But how does it relate to the trail we are following now? This is no Dinotherium hunt." This time she did not intend to be put off.
The blind eyes focused on her disconcertingly. "How much do you think that tribe lost, because of the failure of that one member?"
"I would imagine they went hungry—at least until they could set up another hunt."
"Hunger wasn't very funny in those days, was it?"
"Of course not," Mrs. Rhodes agreed, visualizing a primitive camp, the children bawling, the women standing glumly. "What did they do to that man who—"
"The leader banished him from the tribe, so of course he soon perished. If you're going to hunt Dinotherium, you can't afford any lapses in your organization."
"Also, the others were mad, I'm sure. Had to take it out on someone. But how does that—"
"Communication," Miss Concher said. "Now Australopithecus has a compelling reason to select for that single trait. Note that—the first artificial selection in the history of life on Earth, and for a nonphysical trait. He can't tolerate tribesmen who can't or won't respond to spoken instructions, even if these only take the form of imperative barking. The groups with dumb members will fall on hard times, and their children will starve, while those who are selective will become fine hunting units. They will be capable of driving Dinotherium into the gully and stoning him to death there while he stumbles in the steep sand, and they will eat well and prosper. Communication is the key—the small mouth put to the uses of survival!"
"I concede that," Mrs. Rhodes said, both enlightened and annoyed. "But what—"
"Once you're on that treadmill, you have to continue. You need the big game to feed your increasing numbers, for squirrels and sparrows won't feed an entire tribe for long, and certainly not wild fruit. You become dependent on organization, on the specialization that is the hunt. And you begin to contest with neighboring tribes for the best hunting territory, staking it out, and so your communication is now employed man-against-man. That's a rough game, and if you quit you die. Today an army is helpless when its communications break down. Your size increases and your brain expands, as it must to handle the burgeoning linguistic concepts required to define an effective campaign. Barks meaning 'run,' 'stop' and 'kill' give way to subtler sounds meaning 'run faster,' 'stop over there' and 'kill on command only.' And finally you are not just Australopithecus, you are Homo Erectus. An animal with the single specialized organ so harshly selected for: the brain."
Mrs. Rhodes refused to be diverted. "This trail—"
"I believe," Miss Concher said gently, "that it was not mere coincidence or fleeting convenience that started Australopithecus along the demanding highway of verbal communication. The odds against this seem prohibitive. Some outside agency instructed him. Something forcibly directed him to speak, or somehow arranged it so that he had to communicate in order to survive at all. Something that knew where this process would lead. And that is what we are sniffing out now—that alien influence that shaped us into mastery."
At last Mrs. Rhodes saw the point. If somebody—something, for there could have been no true men then—if some agency had come to show potential man the route to success—
Man had a debt going back two million years.
And now two women, one middle-aged and the other old, were belatedly on the trail of that visitation, that phenomenally important influence. What would they find?
Miss Concher nodded. "It's a little frightening, isn't it? We may not appreciate the truth one bit—but can there be any question of turning back now?"
This close to the answer to the riddle of man's progress? No, of course they could not turn back.
Down the Great Rift Valley they traveled, sniffing out the ancient trace. The natives generally ignored them. What harm could two crazy old women do, with their truckful of junk? They skirted Lake Tanganyika and traversed the length of Lake Nyasa, and the trail continued. At last they stood at the mouth of the Zambezi River, and the trace vanished.
They stood on the shore and looked eastward, Mrs. Rhodes' live eyes seeing no more than Miss Concher's dead ones. Their gruelling weeks of travel and drilling had come to an unhappy halt, for the water held no scent.
"No," Miss Concher said. "This is merely a hurdle. It can not end here." But for once her words lacked conviction. She had been an energumen until this moment, expending energy at a cheerful but appalling rate; now she was an old woman who could not find her knitting.
"A sea-creature?" Mrs. Rhodes suggested, embarrassed by her companion's weakness. She tried to envision a credible object, but without Miss Concher's guidance it manifested as a parody: an ancient octopus struggling rheumatically out of the depths, donning sunglasses and marching up the Rift to the sound of fife and drum to instruct Australopithecus. Ridiculous!
"Unlikely," Miss Concher said. But her bulldog mind was working again, after its hesitation. "Could have been based on the sea-floor, though. Or floating on the surface. The sea is an obvious highway for civilized species—check the map."
Mrs. Rhodes gladly did so. "It's a long coast line. Funny that they should come to this particular place, then make a thousand mile journey overland, when they could have landed so much closer to Lake Victoria..." She paused. "Unless they crossed directly from Madagascar—"
"My diagnosis exactly!" Had it been—or was Miss Concher trying to conceal her lapse? "Let's rent a boat."
What did it matter? They had a mission once more.
The crossing was not so simple as merely "renting a boat," but two weeks later they had negotiated the physical and political hazards and were driving their truck along the west coast of Madagascar. In another two they had spotted the trace again. The trek resumed: east, into the heart of the huge island.
The palms of the shoreline gave way to rice fields and islandlike hills and occasional thatch-roofed earthern houses. Mrs. Rhodes looked up one dusk to meet a pair of large eyes. "Something's watching us," she whispered, startled.
"Describe it," Miss Concher said, unruffled.
She peered at the creature, beginning to make it out in the shadow. "Small, bushy-tailed, head rather like a fox—but it has monkey-feet, and it's clinging to a branch."
"Lemur," Miss Concher said. "Madagascar is their homeland. The few species extant today are a poor remnant of those that ranged the world in past times."
"Not dangerous, then," Mrs. Rhodes said, relaxing.
"Not now. One type, Megaladapis, was larger than a gorilla—in fact, was the largest primate known. And another extinct Lemuridae, Archaeolemur, may have been remarkably cunning, if we are to judge by the precocious development of the temporal lobe during the—"