As one of the earliest fossilized forms of life, a mystery still surrounds the creation of these fossils — formed during a hostile era when the newly formed continents were barren and life was confined to the seas. The age of the Earth is little over 4.5 billion year old, when life first appeared is unknown, some scientists have suggested it could have happened shortly after its creation.
Rock formations from the early Earth outcrop incredibyl rarely. Rare still are fossil from the Archean (4,000 to 2,500 million years ago). Some possible stromatolites from Greenland have been tentatively dated to 3.7 billion years old, but the oldest confirmed microbial mat fossils are from this 3.48 billion year old sandstone from Australia.