But when sex was invented half a billion years ago, in the Cambrian explosion — boom! — suddenly evolution was proceeding by leaps and bounds. And any race that reproduces sexually might very well still argue about the ethics of destroying a unique combination of genetic material even if they’ve always held that such a thing wasn’t alive until the moment of birth."

Don frowned. "That’s like saying it’s a moral quandary to worry about destroying snowflakes. Just because something is unique doesn’t make it valuable — especially when everything in that class of entities is unique."

A chipmunk scampered across the road in front of them. "Besides," continued Don, "speaking of evolution, doesn’t the abortion issue ultimately take care of itself, given enough time? I mean, natural selection obviously would favor those people who actually put into practice being pro-life over those who actually choose to personally have abortions, because every fetus you abort is one less set of your genes around. You wait enough generations, and being pro-choice should be bred out of the population."

"Good grief!" Sarah said, shaking her head. "What a revolting thought! But, even so, that’s only true if the desire for reproductive choice is merely one of passing convenience, and has nothing to do with whether the kid will make it to reproductive age without too many resources being invested. I mean, look at Barb and Barry — they’ve essentially devoted their whole lives to raising Freddie." Barb was Sarah’s cousin; her son was severely autistic. "I love Freddie, of course, but in effect, he’s replaced potential siblings who would have required a fraction of the investment and would have been far more likely to provide Barb and Barry with grandchildren."

"You know as well as I do that a vanishingly small number of abortions are because the fetus is defective," said Don. "Hell, we’ve had abortion for centuries, and only had prenatal screening for decades. Infanticide, that’s another thing, but…"

"Postpartum depression has its evolutionary roots in the mother recognizing that she has insufficient resources to insure that this particular offspring will survive to reproductive age, and so the mother conserves her parental investment by cutting her losses and failing to bond with the infant. No matter how you slice it, evolution will conserve mechanisms that don’t always lead to simply having the most offspring.

Anyway, setting aside abortion, I still think most races will face very similar moral issues as they develop technology that expands their powers. I know the aliens didn’t mention God—"

"That’s right," Don said smugly.

"-but every race that survives long enough will eventually struggle with the ramifications of getting to play God."

It was growing dark; the streetlights flickered on. " ‘God’ is a very loaded term," he said.

"Maybe so, but we don’t have a lot of synonyms for the concept: if you define God as the creator of the universe, all races that live long enough eventually become Gods."

"Huh?"

"Think about it. We’ll eventually be able to simulate reality so well that it will be indistinguishable from… well, from reality, right?"

"One of my favorite authors once said, ‘Virtual reality is nothing but air guitar writ large.’ "

She snorted, then continued: "And a sufficiently complex virtual reality could simulate living beings so well that they themselves will actually think they’re alive."

"I suppose," he said.

"For sure. Have you seen that game The Sims that Carl likes to play? The simulations of reality we can make today are already amazing, and we’ve only had digital computers for — what? — sixty-five years now. Imagine what sort of reality you could simulate if you had a thousand or a million or a billion times more computing power at hand — which we, or any technological race that lives long enough, eventually will. Again, where do you draw the line between life and nonlife? What rights do those simulated lifeforms have? Those are moral issues all races will have to face."

Another couple, also out for a walk, was coming toward them. Don smiled at them as they passed.

"In fact," she continued, "you could argue there’s even some evidence that we ourselves are precisely that: digital creations."

"I’m listening."

"There’s a smallest possible length in our universe. The Planck length: 1.6 x 10^–35 meters, or about 10 times the size of a proton, you can’t measure a length any -20 smaller than that, supposedly because of quantum effects."

"Okay."

"And," she said, "there must be a smallest unit of time, too, if you think about it: since a particle of light has to be either here, at Planck length unit A, or next to it, at Planck length unit B, then the time it takes to move from one unit to the next — the time it takes a photon to click over from being in this Planck space-unit to that Planck space-unit — is the smallest possible bit of time. And that unit, the Planck time, is 10 seconds."

–43

"The Clock of the Short Now," said Don, pleased with himself.

"Exactly! But think about what that means! We live in a universe made up of discrete little bits of space that’s aging in discrete little chunks of time — a universe that has pixels of distance and duration. We are digital at the most fundamental level."

"Quantum physics not as the basic nature of reality, but rather as the — how would you put it? — as a by-product of the level of resolution of our simulated world." He made an impressed face. "Cool."

"Thanks," she said. "But that means our world, with its pixels of time and space, might be nothing more than some far-advanced civilization’s version of The Sims — and that would mean there’s a programmer somewhere."

"I wonder what his email address is," Don said. "I’ve got some tech-support questions."

"Yeah, well, just remember once you open the seal on the universe, you can’t get your money back." They turned a corner. "And speaking of making universes, with particle accelerators we may eventually be able to create daughter universes, budding off from this one. Of course, we won’t create a full-blown universe, with stars and galaxies; we’d just create an appropriate singularity, like the one that our universe burst forth from in the big bang, and then the new universe will make itself from that.

Physics says it’s possible — and I rather suspect it’s only a matter of time before someone successfully does it."

"I get it," said Don. "If you take a step back, that means we could be living in a universe created by a scientist in some parent universe’s particle accelerator."

"Exactly!" said Sarah. "And, look, you know I love following all those debates in the U.S. about the teaching of evolution and intelligent design. Well, I’m an evolutionist — you know that — but I don’t agree with the testimony that the scientists on the evolution side keep giving. They keep saying that science cannot admit supernatural causes, by which they mean that any scientific explanation has to, by definition, be limited to causes intrinsic to this universe."

"What’s wrong with that?"

"Everything is wrong with it," she said. "That definition of science prevents us from ever concluding that we are the product of the work of other scientists, working in a reality above this one. It leaves us with the cockeyed mess of having a scientific worldview that on the one hand freely acknowledges that we will eventually be able to simulate reality perfectly, or maybe even create daughter universes, but on the other hand is constrained against ever allowing that we ourselves might exist in one of those things."

"Maybe science isn’t interested in that question simply because it doesn’t really answer anything," Don said. "I suspect somebody like Richard Dawkins would say, so what if we are the creation of some other intelligent being? That doesn’t answer the question of where that other intelligent being came from."