Orson Card - Earthfall

The trouble was that as the old religion faded, as fewer and fewer diggers took part in the annual raid to steal statues from the mating angels, the diggers' birthrate also seemed to fall off-even as the angels prospered, their population blooming at an almost alarming rate. Whispers began among the diggers that the new religion of the Keeper of Earth was really part of a conspiracy to destroy the diggers so that angels and humans could divide the world between them. Not that many people believed these tales, but enough did that it was a worry. There were those who would exploit such rumors. And, in fact, when Nafai began to hear that it wasn't all the humans but rather just Nafai and those who followed him who were plotting to destroy the diggers, he knew that someone was already seeking to turn these fears to his advantage.

In the meantime, though, the digger birthrate continued falling off, even though the nutrition kvels were higher and higher all the time. And the angels had to expand constantly, burning more patches of forest to put more land under cultivation. All those twins, and none of them getting murdered now in infancy; all those healthy adults, and none of them getting culled by the marauding diggers.

They had been on Earth for twelve years when She-demei called the adult humans together for a meeting. She had finally solved the mysteries, she said. But now there were some new mysteries, and some decisions to be made.

"We've been meddling," said Shcdemei. "As you're all aware, the felling birthrate among the diggers is causing some serious worries among them."

"We're worried too," said Volcmak.

"Yes, well, now I know why it's happening. We did it. We're doing it."

They waited. Finally Mebbekew said, "I didn't know you had such a flair for the dramatic, Shedya. How long do we wait for the other shoe to drop?"

"This is only the first shoe," she said. "The other shoe comes after." There was some nervous laughter. "The problem is, you see, that we've stopped them from believing in their gods. They aren't worshipping anymore. They aren't even stealing fresh statues from the angels. And that's why they aren't having any babies."

"You're telling us," said Elemak, laughing, "that their religion is true?"

"In a word, yes," said Shedemei. "We have a dozen years' worth of close observation of the local digger and angel tribes. Zdorab and I have also made some sampling visits to other digger and angel settlements, and we feel reasonably confident that we have uncovered a universal pattern. For one thing, there's no such thing as an angel village without a digger city nearby, nor a digger city without an angel village within a few hours' walk. This is not an accident. The diggers can't survive without the angels. Specifically, the diggers can't reproduce without worshipping the statues that the angel males create as part of their mating ritual."

"Do I get the impression that the cause is biological rather than theological?" asked Rasa.

"Of course, though it's hard to look at little clay statues and see a biological mechanism," said Shedemei. "It was Zdorab who first pointed out to me that what matters, biologically, may not be the artistry involved in the creation of the statues. It's the spit. The angel men take the clay into their mouths and mix a wet mud out of it, which they use to start the wad that becomes the statue. Every now and then they take another mouthful of mud and wet it. The saliva flows very freely."

The listeners' minds were working rapidly, trying to put things together. "You mean diggers need to rub angel spit on their bodies in order to mate?" asked Dza.

"Not quite," said Shedemei. "The first time we examined the bodies of angels and diggers, we found a little organ-a gland, actually-near the scrotum. It was identical in both species, even though they have no common ancestor with a similar organ. Very puzzling, of course. But we now know the function of the organ. It continuously secrets tiny amounts of a hormone that suppresses the production of sperm. No, let me be clear. It completely shuts down the production of sperm. While the organ is functioning, males are completely, absolutely sterile."

"What a useful little organ," murmured Oykib. Then, louder, "Why would that evolve?"

"It gets worse," said Zdorab.

"There's a tiny flatworm, a microscopic one, that Hves in all the freshwater rivers of this massif. During the rainy season, when the rivers are in flood, this flatworm burrows into beds of firm clay and lays millions of tiny eggs. They don't develop as long as they remain wet. But when the dry season comes and the water subsides, the eggs develop, forming hard littk coatings that hold in what moisture they have. The embryos are ready to hatch at any time. But they can't, because they can't get rid of their own confining shells. So they hibernate, living off their yolks. They use the yolks so slowly that they can live for twenty or thirty years like that. The next rainy season doesn't cause them to hatch, because water doesn't dissolve the shells. Guess what dissolves them."

"Angel spit," said Oykib.

"Amazing boy," said Shedemei. "My prize student." There was some laughter, but they were all waiting for the story to go on. "No other fluid will do it, because the angels have tiny organelles in the saliva-producing cells of their mouths, which secrete an enzyme that has no function whatsoever within the bodies of the angels-but it dissolves the shells of the flatworm eggs. So when the males bring the clay into their mouths, they're not just softening it to make sculptures. They're also dissolving the shells erf" millions of little flatworms. And it just so happens that the dissolved shells contain precisely the one chemical that suppresses the action of the prophylactic gland near the angels' and diggers' scrota. The fertility chemical breaks down very slowly, and the statues contain useful quantities of it perhaps as long as ten years, certainly for five."

Everybody was getting it now. "So when the diggers rubbed the statues all over their bodies. ..." "Were the angels swallowing some of it?" "How much of the fertility chemical does it take?"

Shedemei raised her hands to damp the questions and comments. "Yes, you've got it. The angel males absorb the fertility enzyme by mouth. It doesn't take much of it to shut down the action of the prophylactic gland, and it doesn't recover and start up again for about two weeks, maybe three. So there's a window there in which reproduction can take place. And the digger males have a special absorbent patch on their lower bellies, near the groin, where the chemical can be absorbed quite directly into the bloodstream. Rubbing the statues on their sweating bellies dissolves some of the day, whereupon the dissolved fertility enzyme is taken into the blood and, just as with the angels, it shuts down the prophylactic gland and the digger males are fertile. But because they actually get a great deal less of the enzyme, the fertility window is only a few days long for them. Doesn't matter, though. Where the angels make their statues once a year and have to score a reproductive hit that one time, the diggers are culturally able to worship the statues any time. In effect, the statues enable them to reproduce whenever they want. They just have to pray first."

"That is the most absurdly complicated, unlikely, ridiculous mechanism I've ever heard of," said Issib.

"Exactly," said Shedemei. "There is no chance that it evolved naturally. Why would the diggers and angels independently evolve identical organs that make them sterile? There's no evolutionary advantage in it. Why didn't the angels simply die out before they ever started making their sculptures in the first place? Why didn't the diggers die out before they ever discovered the virtues of rubbing angel statues all over themselves? And why would a species of flatworm just happen to require a special chemical in angel saliva in order to hatch their eggs? And why did the angels develop a chemical with no use in their bodies except to dissolve the shells of the flatworms?"