"What's to stop the angels from taking off and starting a colony where there aren't any diggers?" asked Protchnu. "Nothing," said Shedemei, "and I'm sure it's happened many times. But they can only live where they can find clay that supports the flatworms. That means that they can only live where there's a pattern of rainy season flooding, and they can only live at elevations where the flat-worm can survive. It's a pretty narrow range, common enough on this massif but not elsewhere. And the diggers range far and wide. I don't think there's anywhere that angels can go without a digger finding them sooner or later. When the digger finds them, he goes home and reports that he's found a new spot that's favored by the gods, and so they send out a colony. It's actually to the benefit of the angels. Without diggers devouring their young, their populations reach climax very quickly."

"Are you suggesting," said Nafai, "that we should let the diggers go back to kidnapping and eating angel infants?"

"That's the question," said Shedemei. "That's really the question, isn't it?"

"Does any of this," asked Chveya, "have to do with the evolution of intelligence among the angels and diggers?"

"Some, I think," said Shedemei. "The way the angel females select their mates is by the intricacy, beauty, originality, and accuracy of their sculptures. Obviously, the more intelligent and creative the angel male, the better his chances of reproducing early and often. For the diggers, it's a little different. In order to kill angels, they have to be devious and smart. We don't see it that much now, of course, because the diggers are so smart that the angels had almost given up trying to stop them. But we've all seen the traps that the angels set at the perimeter of their villages. It may be that the stupid diggers used to get caught in such traps. NoW they recognize and evade them easily. But perhaps their very intelligence evolved because only the smart ones got through the angel traps ki order to steal statues and baby angels."

"In other words, intelligence evolved naturally," said Chveya. "It's this symbiotic relationship that's unnatural."

"Not just unnatural," said Shedemei. "Human-made."

"How can you know that?" asked Protchnu.

"Because we believed that it couldn't be natural. And we knew that humans ceased to live on Earth at the time of the emigration that settled Harmony and, no doubt, other worlds as well. As we searched with the Index, we found that the one part of history where the ship's library had no useful information was human life at the time of the emigration."

Zdorab, the librarian, took over here. "Now, we have always imagined that this was because it was such a terrible time that they tried to forget it. There were implications of wars using weapons so dreadful that they turned the Earth for a while into a ball of ice. That's what the Oversoul himself believed. But then something Nafai said to me one time made me realize that this paucity of information really wasn't believable. He said, ‘How could the people who saved humanity by leaving Earth have allowed themselves to be so completely forgotten?' And I thought. Of course they couldn't. So I started searching the computers on the ship, the ones that tren't tied to the Oversoul. And I found what I was looking for. A database that the Over-soul has no conscious access to. It's called, as nearly as I can translate it, The Book of the Sins of the Human Race"

"Sins?" asked Mebbekew.

"Well, it's the most economical translation. It's a term that means ‘willful mistakes.' ‘Crimes of avoidable negligence,' perhaps. I thought sin was a pretty good way of summing it up."

"What does the book contain?" asked Nafai.

"I only just found it. I haven't read it all, and I'd be glad to have any of you who have the time and interest help me in the translation. The language is close to several known languages but it's very very old and the Oversoul hasn't been updating it because he wasn't conscious that it was there. The thing is, one of the first things I found was the explanation for how the angels and diggers began. It was one of the ‘sins,' you see."

Zdorab brought up a document on the computer screen nearest to him and began to read aloud.

"We have sinned by fiddling with the genes of animals, giving them intelligence without freedom, talent without power, desires without hope. We used them for our amusement, displaying their paintings and sculptures and music and dance while keeping the painters and sculptors, the musicians and dancers in prisons. If they escaped their freedom was worthless because they could have children only in captivity. This was an abomination, and the Keeper of Earth revolted against it, driving away the slavemakers and slavekeepers, and setting the little ones free."

Shedemei spoke up. "I think the possible connection with diggers and angels should be obvious. The angels are the ones who still do some kind of art, but that's what they were bred for, perhaps. Zdorab and I can't think what the diggers were originally bred to do."

"Dig," said Elemak.

"Possibly," said Shedemei. "Just because the Book of Sins mentioned only the intelligent animals created in order to entertain humans doesn't mean there weren't also animals that were genetically enhanced in order to do more menial tasks. Like seeking out underground deposits of various minerals, for instance. Or simply digging tunnels."

"Sewer work," said Elemak.

"As I said, we don't know," said Shedemei. "I think there's a good chance that the diggers' ancestors weren't very intelligent at all. Enhanced physically, but not mentally. But they survived because they were bright enough, or lucky enough, to live close to a tribe of angels and perhaps simply by chance they rubbed themselves with the statues."

"Or maybe they survived," said Zdorab, "because the diggers lived in burrows and the angels lived in caves, and so when the Earth went into a profound ice age they both survived underground and developed their symbiosis there."

"Or maybe they were taught to do it in a dream," said Luet,

"Well, there we are," said Shedemei. "It might all have been planned and controlled. Even as the Keeper of Earth drove out the human race, she might have been planning to replace our ancestors with new species. She might have been manipulating them both to help them both evolve intelligence."

"And in the meantime," said Zdorab, "to make them symbiotic so that they couldn't possibly survive without each other The old humans created the fiatworms and made it so that the angels' ancestors had to sculpt clay or they couldn't reproduce. Perhaps they didn't give any of the other captive animals a mechanism that would allow them to get a supply of the chemical they needed without human intervention. Only the diggers found their own way to piggyback on the angels' survival method. Who says the Keeper of Earth couldn't have put it all together that way? Perhaps it was because of the Keeper that humans first developed the flatworm vector for creating the chemical the angels needed. Perhaps the Keeper planned it all."

"Whatever the Keeper is," said Meb.

"I have another idea," said Elemak. "What if there's no such thing as the Keeper? Those dreams you had back on Harmony, you were all so sure they came from this supposed Keeper because the Oversoul knew nothing about the diggers and the angels. But now we find out that the Oversoul had all this information in his databanks, only he simply couldn't consciously access it. So those dreams could have come from the Oversoul all along, without his knowing it, right? And now we don't have to imagine some mechanism for sending dreams fester than light across the space between Earth and Harmony."

"Very good theory," said Shedemei. "But it doesn't explain Kiti making a perfect likeness of Nafai a hundred years before we arrived here."