Skip to content The TNA world that came before the RNA one – The question of how non-living chemicals emerged from the so-called primordial soup to give rise to life on Earth is one of the most intriguing in science. Finding an answer might not only help explain our origins but could give us important clues as to that other intriguing question of whether or not we are alone in the universe. Once it was recognised that DNA is key to the molecular self-replication that underpins life, chemists have sought to understand the origins of this double-helical molecule in that primordial age. It was quickly assumed that RNA, a single-stranded nucleic acid, may have been the precursor genetic material to DNA, and the RNA world hypothesis was born. But what gave rise to RNA? Chemists in the US are starting to home in on another nucleic acid, TNA: threose nucleic acid.