Origin of Life was apparently very early in Archean.

Evidence of Archean life:

• Fractionated carbon isotopes at 3.8 Ga (Isua Fm., Greenland)
• Filaments of cyanobacteria (blue-green algae) in 3.4 Ga cherts (in western Australia, South Africa)
• Stromatolites at 3.3-3.5 Ga (Warrawoona Group, Australia)

Earliest life was probably exceedingly simple: far simpler than any modern form.
Would have been:

• Anaerobic: evolved outside the presence of free oxygen (free oxygen would probably poison it!)
• Heterotrophic: a consumer, absorbing molecules from water
• Prokaryotic: no nucleus nor other complex organelles

Once thought to have appeared in "quite little pond" ("primordial soup").
More likely: formed near the (then more active) oceanic vents along mid-ocean ridges:

• Abundant energy supply and mineral supply
• Far more common in Archean than now (due to higher geothermal activity)
• Ocean water would protect early life from UV rays
• Even today many exceedingly simple prokaryotes live near vents, black smokers, etc.

As fuel supply decreased, various new forms appeared from among the proto-organisms:

• Photosynthesizers ("blue green algae"), first to use sunlight directly.
• 1rst order consumers: absorb other cells.

With photosynthesizers come free oxygen: begin to change global atmosphere. Has most direct effect as the Proterozoic begins.

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Last modified: 2 January 2008