“Hold on,” said Wheaton. “Garden has already tried dozens of ways to forestall the destruction of humanity, so there are lots of timestreams in which one of these species wipes out all rivals and rules this bit of the galaxy. The other one was probably destroyed before the victor ever came near us, so we’re not the ones who snuffed them out. All we’re doing now is creating one slim timestream in which the human race survives. It is not so very much to take for ourselves, compared with what they’ve taken already.”

“So you’re arguing in favor of xenocide?” asked Ram.

“Not at all,” said Wheaton, looking horrified. “Nothing of the kind! Garden has endured for eleven millennia with tight restrictions on their ability to develop high technology, right?”

“Yes,” said Noxon.

“And that was a lid placed on the planet by other humans, right?”

“By computers,” said the expendable, “but obeying human orders.”

“So if we go into the past and put such a lid on both these species,” said Wheaton, “we’re doing to them nothing that we haven’t already done to ourselves.”

“To one portion of our species,” said Noxon. “Earth didn’t put any such lid on themselves.”

“We don’t have to destroy their whole biota in order to set up colonies here, do we?” asked Wheaton.

“It depends on what proteins they produce, and whether we can digest enough of them,” said Ram.

“I don’t suppose now would be a good era in which to make our investigations,” said Wheaton.

“You want to go into the past and see them early in their evolution,” said Noxon.

“I am what I am,” said Wheaton. “But I’m also right.”

“Put us back a few hundred thousand years ago,” said the alpha mouse, “and we’ll be their lid.”

“The mice have already suggested,” said Noxon, “that ten of our ships go to the other world, and ten stay here.”

“I wonder if versions of you are saying exactly the same thing on all nineteen of the other ships,” said Ram.

The expendable answered. “The exact wording is quite different, but yes, on every ship you have reached approximately the same point in your discussion.”

“What have the others decided?” asked Ram.

“They’re all asking their expendables what the others decided.”

“We haven’t decided anything,” said Wheaton. “But the only sensible thing is to go back in time, split the fleet in half, and explore both worlds to see what damage we might have to do in order to use them.”

“But we don’t even know what the sentient species look like on either world,” said Noxon. “How will we know which life forms in the past are going to evolve into them?”