Researchers suggest RNA and DNA got their start from RNA-DNA chimeras
(PHYSorg.com Chemistry)

A pair of researchers with the Scripps Research Institute has suggested that RNA and DNA got their start billions of years ago from RNA-DNA chimeras that contained RNA and DNA building blocks. In their paper published in the journal Nature Chemistry, Subhendu Bhowmik and Ramanarayanan Krishnamurthy outline their theory and argue that it makes more sense than the traditional explanation for how life got its start on Earth.