Archean Eon

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
Living Stromatolite - 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.