An article in the Joyce Laboratory newsletter called it “The Immortal Molecule.” Dr. Joyce’s molecule is a form of RNA, or ribonucleic acid, which plays Robin to DNA’s Batman in Life As We Do Know It, assembling proteins in accordance with the blueprint encoded in DNA. Neither RNA nor DNA is alive by itself, any more than any other chemical, like bleach, or a protein. But in Dr. Joyce’s test tube, his specially engineered RNA molecule comes close, copying itself over and over, and evolving.

But, Dr. Joyce says, “We really would hope for more from our molecules than just replicating.”

Reproduction is the job of any life, he explained, but Earthly organisms have evolved a spectacular set of tricks to improve the odds of success — everything from peacock feathers to whale songs. Dr. Joyce’s molecules have not yet surprised him by striking out on their own to invent the molecular equivalent of writing a hit pop song.

It is only a matter of time, he said, before they do.

“Our job is to give them the running room to do that,” Dr. Joyce said.

The deeper philosophical and intellectual ramifications of test tube life are as enormous as they are unknown. The achievement would probably not come with sci-fi drama, say scientists who are squeamish about such matters anyway, saying such speculation is beyond their pay grade. No microbe is going to leap out of the Petri dish and call home, or turn the graduate students into zombies. Indeed, given the human penchant for argument and scientists’ habit of understatement, it could be years before everybody agrees it has been done.

“The ability to synthesize life will be an event of profound importance, like the invention of agriculture or the invention of metallurgy,” Freeman Dyson, a mathematician and physicist at the Institute for Advanced Study in Princeton, wrote in an e-mail. “Nobody can tell in advance what will come of it.”

On Earth, all life as we know it is based on DNA, the carbon-based molecule that contains the instructions for making and operating living cells in a four-letter alphabet along its double-helix spine.

The possibilities of a second example of life are as deep as the imagination. It could be based on DNA that uses a different genetic code, with perhaps more or fewer than four letters; it could be based on some complex molecule other than DNA, or more than the 20 amino acids from which our own proteins are made, or even some kind of chemistry based on something other than carbon and the other elements that we take for granted, like phosphorous or iron. Others wonder whether chemistry is necessary at all. Could life manifest itself, for example, in the pattern of electrically charged dust grains in a giant interstellar cloud, as the British astronomer and author Fred Hoyle imagined in his novel “The Black Cloud”?