premise: History of Earth dates back billions of years.
hypothesis: History of Earth . Earth formed around 4.54 billion years ago by accretion from the solar nebula . The Hadean Eon represents time before the reliable ( fossil ) record of life beginning on Earth ; it began with the formation of the planet and ended at 4.0 billion years ago as defined by international convention . The earliest undisputed evidence of life on Earth dates at least from 3.5 billion years ago , during the Eoarchean Era after a geological crust started to solidify following the earlier molten Hadean Eon . There are microbial mat fossils such as stromatolites found in 3.48 billion-year-old sandstone discovered in Western Australia . Life remained mostly small and microscopic until about 580 million years ago , when complex multicellular life arose , developed over time , and culminated in the Cambrian Explosion about 541 million years ago .