Benner believes there may be some organisms hiding on Earth today that are based not on DNA and proteins but on a more primitive type of biochemistry. A number of researchers now theorize that DNA-based life evolved from an RNA-based predecessor. RNA is an unusual molecule that can both store genetic information and act like an enzyme, cutting apart other molecules or putting them together. Benner is convinced that 4 billion years ago, Earth was home to simple RNA-based organisms that could find food, grow, reproduce, and even evolve. Over time, some of these developed the ability to build proteins and switched to double-stranded DNA to carry their genes.