Pre RNA World
The RNA world hypothesis is based in the theory that RNA preceded DNA at an eary stage in the evolutionary history of life on Earth, the hypothesis predicts that self-replicating RNA molecules proliferated before the evolution of DNA and proteins. Although this is heavily supported by contemporary research however it is not without its flaws. These flaws surround the stability and creation of RNA. To solve these problems a 'Pre-RNA World' was introduced. The hypothesis suggests that before RNA there was a much simpler molecule that still had "both catalytic activity and information storage capabilities" .
There is now strong evidence indicating that an RNA World did indeed exist on the early Earth. The smoking gun is seen in the structure of the contemporary ribosome. The active site for peptide-bond formation lies deep within a central core of RNA, whereas proteins decorate the outside of this RNA core and insert narrow fingers into it. No amino acid side chain comes within 18 Å of the active site. Clearly, the ribosome is a ribozyme and it is hard to avoid the conclusion that, as suggested by Crick, the primitive ribosome could have been made entirely of RNA.
Although it is widely accepted that RNA preceded DNA their is also a pre-RNA world theory in which simpler biomolecules would, through evolution, become what eventually became RNA. 
- ↑ Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts and Peter Walter (2008) Molecular Biology of the cell, 5th edition, New York: Garland Science p.402
- ↑ Robertson M, Joyce G. The Origins of the RNA World. Cold Spring Harbor Perspectives in Biology [Internet]. 2010 [cited 3 December 2017];4(5):1-12. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3331698/
- ↑ Klyce B. The RNA World and other origin-of-life theories. by Brig Klyce [Internet]. Panspermia.org. 2017 [cited 3 December 2017]. Available from: http://www.panspermia.org/rnaworld.htm