For starters, there are plenty of evolutionary biologists who believe that evolution, given long enough, was likely to create a smart, articulate species  not our species, complete with five fingers, armpits and all the rest  but some social species with roughly our level of intelligence and linguistic complexity.

And what about the chances of a species with a moral sense? Well, a moral sense seems to emerge when you take a smart, articulate species and throw in reciprocal altruism. And evolution has proved creative enough to harness the logic of reciprocal altruism again and again.

Vampire bats share blood with one another, and dolphins swap favors, and so do monkeys. Is it all that unlikely that, even if humans had been wiped out a few million years ago, eventually a species with reciprocal altruism would reach an intellectual and linguistic level at which reciprocal altruism fostered moral intuitions and moral discourse?

There’s already a good candidate for this role  the chimpanzee.

Chimps, some primatologists believe, have the rudiments of a sense of justice. They sometimes seem to display moral indignation, “complaining” to other chimps that an ally has failed to fulfill the terms of a reciprocally altruistic relationship. Even now, if chimps are gradually evolving toward greater intelligence, their evolutionary trajectory may be slowly converging on the same moral intuitions that human evolution long ago converged on.

If evolution does tend to eventually “converge” on certain moral intuitions, does that mean there were moral rules “out there” from the beginning, before humans became aware of them  that natural selection didn’t “invent” human moral intuitions so much as “discover” them? That would be good news for any believers who want to preserve as much of the spirit of C. S. Lewis as Darwinism permits.

Something like this has been suggested by the evolutionary psychologist Steven Pinker  who, as a contented atheist, can’t be accused of special pleading.

Mr. Pinker has noted how the interplay of evolved intuition and the dynamics of discourse tends to forge agreement on something like the golden rule  that you should treat people as you expect to be treated. He compares this natural apprehension of a moral principle to the depth perception humans have thanks to the evolution of stereo vision. Not all species (not even all two-eyed species) have stereo vision, Mr. Pinker says, but any species that has it is picking up on “real facts about the universe” that were true even before that species evolved  namely, the three-dimensional nature of reality and laws of optics.