3.8 to 2.5 billion years ago
- the atmosphere was different from
what we breathe today it was - likely a reducing atmosphere of
methane, ammonia and other gases which would be toxic to most life
- crust cooled enough that rocks and continental plates began to
form. 
- early in the Archaean life first
appeared
- oldest fossils date to roughly 3.5 billion years ago, and consist of
bacteria
microfossils
- all life during the more than one billion years of the Archaean was
bacterial or Archaean (thermophillic bacteria-like organisms)
stromatolites
are colonies of photosynthetic bacteria which have been found as fossils
in Early Archaean rocks of South Africa and Western Australia.
Stromatolites increased in abundance throughout the Archaean, but began to
decline during the Proterozoic.
- they are not common today.
Here I am inside the safety
zone of a fumarole at Rincon de la Veija
Costa Rica getting close to my earliest ancestors the Archaea.
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