section_path: Origins/Origin of life
section_name: Origin of life
paragraph_text: Origin of life
  
  Small molecules needed for life may have been carried to Earth on meteorites, created at deep-sea vents, or synthesized by lightning in a reducing atmosphere. There is little experimental data defining what the first self-replicating forms were. RNA may have been the earliest self-replicating molecule, as it can both store genetic information and catalyze chemical reactions.
  
  Cells emerged around 4 billion years ago. The first cells were most likely heterotrophs. The early cell membranes were probably simpler and more permeable than modern ones, with only a single fatty acid chain per lipid. Lipids spontaneously form bilayered vesicles in water, and could have preceded RNA.