Seeking alien life forms, right here on earth

Generations of scientists, children and science fiction fans have grown up presuming that humanity’s first encounter with alien life will happen in a red sand dune on mars, or in an enigmatic radio signal from some obscure star.

But it could soon happen right here on earth, according to a handful of chemists and biologists who are using the tools of modern genetics to try to generate the Frankensteinian spark that will jump the gap separating the inanimate and the animate. The day is coming, they say, when chemicals in a test tube will come to life.

By some measures, Gerald F Joyce, a professor at the Scripps Research Institute here, has already crossed that line, although he would be the first to say he has not yet.
Biologists do not agree on what the definition of life should be or whether it is even useful to have one. But most do agree that the ability to evolve and adapt is fundamental to life.

And they also agree that having a second example of life could provide insight to how it began and how special life is or is not in the universe, as well as a clue for how to recognise life if and when we do stumble upon it out there among the stars.

“Everything we know about life is based on studies of life on Earth,” said Chris McKay, a researcher at NASA’s Ames Research Laboratory in Mountain View, Calif. Joyce said recently: “It drives me crazy when astronomers say, ‘Surely the universe is pregnant with life.’ If we have an earth-like planet, what are the chances of life arising? Is it one in a million? Is it one in two? I don’t see how you can say.”

He continued, “If you had a second example of life, even if it were synthetic, you might know better. I am betting we’re just going to make it.”

Four years ago Joyce and a graduate student, Tracey A Lincoln, now a researcher at the University of Massachusetts Medical School, evolved a molecule in a test tube that could replicate and evolve all by itself, swapping little jerry-built genes in a test tube forever, as long as it was supplied with the right carefully engineered ingredients.

An article in the Joyce Laboratory newsletter called it “The Immortal Molecule.” 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 Joyce’s test tube, his specially engineered RNA molecule comes close, copying itself over and over, and evolving.

But, 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. 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.

Matter of time
It is only a matter of time, he said, before they do. “Our job is to give them the running room to do that,” 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 that it has been done.

“The ability to synthesise 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 email. “Nobody can tell in advance what will come of it.”

On earth, all life as we know 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 Fred Hoyle, the British astronomer and author, imagined in his novel “The Black Cloud”?

Joyce said that his RNA replicators would count as such a “second example, albeit one constructed as a homage to our ancient ancestors.” So far, he said, his work with Lincoln has shown that manmade molecules can evolve over successive generations.

“They can pass information from parent to progeny, they can mutate,” Joyce said. “They can win or die. The molecules are doing it all. We’re just keeping the lights on.”

Joyce’s molecules may not be clever enough yet to qualify as life in his view, but all sorts of alternatives are being explored in other labs.