Appendix B

From “the RNA World” or Another World?

In view of the DNA-RNA-protein team impasse, some researchers have offered “the RNA world” theory. What is that? Instead of asserting that DNA, RNA, and proteins originated simultaneously to produce life, they say that RNA by itself was the first spark of life. Is this theory sound?

In the 1980’s, researchers discovered in their laboratory that RNA molecules could act as their own enzymes by snipping themselves in two and splicing themselves back together. So it was speculated that RNA might have been the first self-replicating molecule. It is theorized that in time, these RNA molecules learned to form cell membranes and that finally, the RNA organism gave rise to DNA. “The apostles of the RNA world,” writes Phil Cohen in New Scientist, “believe that their theory should be taken, if not as gospel, then as the nearest thing to truth.”

Not all scientists, though, accept this scenario. Skeptics, observes Cohen, “argued that it was too great a leap from showing that two RNA molecules partook in a bit of self mutilation in a test tube, to claiming that RNA was capable of running a cell single-handed and triggering the emergence of life on Earth.”

There are other problems as well. Biologist Carl Woese holds that “the RNA world theory . . . is fatally flawed because it fails to explain where the energy came from to fuel the production of the first RNA molecules.” And researchers have never located a piece of RNA that can replicate itself from scratch. There is also the issue of where RNA came from in the first place. Though “the RNA world” theory appears in many textbooks, most of it, says researcher Gary Olsen, “is speculative optimism.”

Another theory that some scientists have espoused is that our planet was seeded with life that came from outer space. But this theory does not really address the question, What originated life? Saying that life comes from outer space, notes science writer Boyce Rensberger, “merely changes the location of the mystery.” It does not explain the origin of life. It merely sidesteps the issue by relocating the origin to another solar system or galaxy. The real issue remains.