In Lab, Clues To How Life Began
MICHELE NORRIS, host: ..TEXT: From NPR News this is All Things Considered. I'm Michele Norris.
MELISSA BLOCK, host:
And I'm Melissa Block. Billions of years ago, the first life on Earth emerged from a primordial stew of chemicals. Exactly how that happened is a central question in biology. Now, two researchers have created some molecules that can do remarkably lifelike things, as NPR's Nell Greenfieldboyce explains.
NELL GREENFIELDBOYCE: If you ask biologist Gerald Joyce to describe the fateful day in Earth's history when non-living chemicals first transformed themselves into life, he'll say, oh, yeah, that day.
Dr. GERALD JOYCE (Biologist, Scripps Research Institute): Yeah, it was a late Tuesday afternoon and the sun was a little dimmer in those days. But no, I mean, we don't know exactly how it happened or even nearly exactly how it happened.
GREENFIELDBOYCE: He says it had to have been roughly four billion years ago. Somehow, a bunch of chemicals came together into something that could copy itself and evolve.
Dr. JOYCE: That's what we and others are interested in because that's sort of, you know, the tipping point between chemistry before and biology after.
GREENFIELDBOYCE: He and his colleague Tracey Lincoln work at the Scripps Research Institute in California. They've now come up with some simple molecules that actually can replicate and sort of evolve, at least within the limits of their little test tube world. I asked Joyce if he felt they had synthesized life.
Dr. JOYCE: No. So, you know, we need to be really careful here. This thing is not alive.
GREENFIELDBOYCE: Do you think someone could argue that it is alive?
Dr. JOYCE: I think someone could. In fact, I know people who have, you know. But most - and I'm not trying to be cute here - most, including myself, very strongly believe this is not yet, or at least not yet it.
GREENFIELDBOYCE: The reason he says it's not life is that it doesn't have the capacity for open-ended evolution. The molecules can't develop any totally new tricks. But what they can do has got scientists pretty excited. The molecules are short bits of RNA. That's a chemical cousin to DNA, and it may have existed before DNA in life's history. The first thing Joyce and Lincoln managed to do was develop a couple of short stretches of RNA. They were actually able to make copies of each other over and over, as long as they were given the right parts to put together. Joyce says he remembers the day when his colleague realized that the molecules really were replicating.
Dr. JOYCE: Well, she just came, you know, running into my office with, you know, with the data in her hands. So, it was one of those kind of, oh boy, moments.
GREENFIELDBOYCE: But even though no one had done this before, he says something that just copies itself over and over again is, well, kind of boring. He wanted to see if the molecules could be a bit more creative. So Joyce and Lincoln developed more self-replicating RNA pairs. They made a dozen of them all slightly different but similar enough that their basic parts could mix and match.
Dr. JOYCE: OK, so now there are lots of replicators. And then we put the whole mix of replicators in a pot at the same time with a whole collection of parts and let them compete to see who can use the parts the most efficiently.
GREENFIELDBOYCE: The RNA pairs got busy making exact copies of themselves, but sometimes an RNA molecule would grab a different part and make a new combination, a kind of mutant replicator that then copied itself. And a few of these mutants were really, really good at making copies.
Dr. JOYCE: And then as many generations of growth proceeded, the fit ones dominated the population.
GREENFIELDBOYCE: A report on this experiment was published this week by the journal Science. It's impressed other scientists interested in early life. Andy Ellington is a biochemist at the University of Texas at Austin.
Dr. ANDY ELLINGTON (Biochemist, University of Texas): The significance here is the events that Gerry has shown in the test tube is equivalent in many ways to an event that must have happened many billions of years ago.
GREENFIELDBOYCE: An event, he says, that led to us.
Dr. ELLINGTON: We are descendants of a long path that started with some molecules that are doing exactly what Gerry's molecules have done, which is replicate and acquire functionality.
GREENFIELDBOYCE: Ellington says people who doubt evolution have argued that simple molecules could never do those things, but this experiment shows they can. Nell Greenfieldboyce, NPR News.