Above: Group of 3.4 billion year old tubular fossil forms (David Wacey/UWA)
What happened during this time?
The oldest indirect evidence of fossil bacteria is found from Western Australian Paleoarchean rocks
Cyanobacteria probably present
Microbially induced sedimentary structures (MISS) from Dresser Formation in Pilbara, Australia (3.48 Ga)
Although, there is evidence indicating "the black cherts formed during precipitation from silica-rich, carbon-bearing hydrothermal fluids in vein systems and vent-proximal seafloor sediments. Given the volcanic setting and lack of organic-rich sediments, we speculate that the vent-mound systems contain carbon derived from rock-powered organic synthesis in the underlying mafic-ultramafic lavas, providing a glimpse of a prebiotic world awash in terrestrial organic compounds" (Rasmussen & Muhling 2023)
It is probable that these structures were abiotic in origin and not evidence of early bacterial life
Ten-micrometre tubular microfossils found in between sand grains in a 3.4 billion-year-old sandstone.
The oldest stromatolites date back to about 3.43 billion years old (Wacey et al. 2011).
These fossil stromatolites have layers similar to those seen in living stromatolites
Evidence of structures 3.46 Ga have been found to be inorganic, and not bacteria (Brasier et al. 2014): elongated filaments were created by minerals forming in hydro-thermal systems.
Secondary structures interpreted as simple filamentous microfossils have been recovered from the layers.
Archaea were probably present during this time
Possible evidence of non-oxygen-generating photosynthesis (Czaja 2013)
Purple bacteria probably developed photosynthesis first
The last universal common ancestor (LUCA) of all life on Earth existed during this era
Continent formation begins, with increasingly larger land masses emerging from the oceans
Possible first super-continent, Vaalbara formed around 3.2 Ga
Evidence from similar sedimentary sequences on the South African Kaapvaal craton and the West Australian Pilbara craton