Fossil Evidence of Early Life Forms

3-2 A weathered outcrop with conical stromatolites from the Tooganinnie Formation (McArthur Group), Northern Territory, Australia. Dated at 1.6Ga. A cm scale is shown at the left (courtesy William Schopf). 

We are uncertain just how life originated, but a reasonable first step in the development of organisms was the non-biological synthesis of those compounds of carbon upon which living systems are 

Stanley Miller (1953) conducted pioneering experiments that have had a profound influence on subsequent thinking. He set out to determine if organic chemicals could be formed from water and the various gases that were presumed to have existed in the atmosphere 4Ga ago. An atmosphere containing methane, ammonia, and hydrogen as its 

Eon/era Period Began Major events in the history of life 

Archean 3.8Ga Origin of life prokaryotes fluorish photosynthetic cells liberate oxygen 

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