> See also: > - [[Microbiology]] # Origin of Life history/timeline of biological research or origins of life (endosymbiosis/biogenesis) ## Spontaneous Generation Before modern microbiology, many believed that “something came from nothing” when considering the origins of life - The **swan neck** experiment conducted by Louis Pasteur was crucial in disproving the concept of spontaneous generation ## Chemical Evolution (Abiogenesis) life didn’t exist at one point before living organisms existed and were able to evolve, chemical compounds underwent their own form of “evolution” 1. a 2. Simple organic molecules formed early polymers that vastly increased the versatility of biological molecules 3. A lot of evidence supports the theory that RNA came before DNA and was one of the first self-replicating systems via ribozymes (catalytically active RNA complexes) ## The RNA World Hypothesis It is theorized that RNA came before both DNA and proteins - RNAs - theorized that some RNAs grew on crystals (similar to how DNA backbone was able to bind to mica crystals, aiding in determining its periodicity) - Peptide bond formation (peptidyl transferase) is catalyzed by RNA - Certain adenines and uracils are universally conserved across ribosomes from different organisms Small molecules are formed first during chemical evolution/abiogenesis. - Adenine is a tetramer of the very simple HCN molecule - Adenine is extremely close to the molecule of ATP, a crucial energy carrier within biology DNA is more stable than RNA, and due to the highly similar structure of their monomers, the possible evolution from RNA → DNA seems very plausible - If RNA used to code for proteins, at some point a flip would have occured where DNA became the predeccessor for RNA synthesis