Scientists long thought that when RNA kick-started life on Earth 4 billion years ago, it could form only small, simple structures. But new research shows that naturally occurring RNA molecules can also adopt large, sophisticated geometries, like filaments and cages. Now, scientists wonder whether the structures were present at life's beginning.
According to an idea known as the RNA world hypothesis, RNA-based life-forms preceded modern ones that use DNA and protein. RNA, a molecular cousin of DNA, still plays roles in modern cells but does not serve as the primary genetic material. By comparison, primordial species used RNA to store genetic information and to catalyze reactions as stand-in enzymes.
