The fossil record provides evidence of the history of life:

Life originated over 3.5 billion years ago; - prokaryotic cells already existed 3.5 billion years ago; - eukaryotic cells originated maybe 1.8 billion years ago;- photosynthesis expanded at a similar time, and caused an increase in the oxygen concentration of the Earth's atmosphere; - multicellular life appear first, in soft-bodied animals, in the Ediacarian faunas of 670 - 550 million years ago; - hard-bodied animals evolved about 550 million years ago and their appearance led to a much richer fossil record, starting with the Cambrian;- terrestrial ecosystems were colonized from the Ordovician onward, and the fossil record provides good evidence concerning the evolution of reptiles, and the origin of birds and of mammals from reptilian ancestors. http://www.blackwellpublishing.com/ridley/tutorials/Fossils_and_the_history_of_life_Summary.asp