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Scientists in Britain have made a breakthrough in their research into the origins of life on earth: How RNA Got Started. The new findings map out a series of simple, efficient chemical reactions that could have formed molecules of RNA, a close cousin of DNA, from the basic materials available more than 3.85 billion years ago, researchers report online May 13 in Nature. “This is a very impressive piece of work — a really excellent analysis,” comments chemist James Ferris of the Rensselaer Polytechnic Institute in Troy, N.Y. The new research lends support to the idea that RNA-based life-forms were the first step toward the evolution of modern life. Called the RNA world hypothesis, the idea was first proposed some 40 years ago. But until now, scientists couldn’t figure out the chemical reactions that created the earliest RNA molecules. Today, DNA encodes the genetic blueprint for life — excluding some viruses, for those who consider viruses living — and RNA acts as an intermediary in the process, making protein from DNA. But most scientists think it’s unlikely that DNA was the basis of the origin of life, says study coauthor John Sutherland of the University of Manchester in England. Information-bearing DNA holds the code needed to put proteins together, but at the same time, proteins catalyze the reactions that produce DNA. It’s a chicken-or-egg problem. Scientists don’t think that DNA and proteins could have come about independently — regardless of which came first — and yet still work together in this way. It’s more plausible that the first life-forms were based on a single molecule that could replicate itself and store genetic information — a molecule such as RNA (SN: 4/7/01, p. 212). RNA world proponents speculate modern DNA and proteins evolved from this RNA-dominated early life, and RNA in cells today is left over from this early time. While reactions to make RNA from ancient precursors worked on paper, the chemistry didn’t work in the lab. And some scientists thought even RNA molecules were too complex to have spontaneously formed in the primordial soup. Sutherland and his colleagues have shown the reactions are possible.
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