The New Beginnings of January Precambrian Era:

Although the Precambrian contains some seven-eighths of Earth's history, its fossil record is poor, with the majority of fossils being the stromatolites that are often heavily metamorphosed or deeply buried. However, preserved cells have been discovered at selective sites, such as the 2.0 billion yar old Gunflint Formation. The earliest life forms were prokaryotes (eubacteria or archaea) that evolved in the seas, possibly as early as 3.8 Ba. The first were possibly chemotrophs existing in an anoxic world and producing H2Scyanobacteria or CO2, which were followed by photosynthetic cyanobacteria before the end of the Archaean some 2.5 billion years ago. When the Eukaryotes (single-celled organisms with a nucleus) evolved through Endosymbiosis is disputed, with claims as early as 3.4 billion years ago, but with less equivocal fossils dating from 1.8 to .8 billion yars ago. With the eukaryotes comes sexual reproduction, enabling genetic diversity and  Cnidarianthe concomitant ability to adapt to and survive environmental changes. Multi-celled, soft-bodied marine fossil organisms (the metazoans), the so-called Ediacara fauna, are found in strata dating between 590 to 700 million years ago. The first mineralized fossils appear after the Ediacaran, but before Cambrian begins at around 580 - 590 my; they comprise ambiguous parts, possibly denticles and plates and tubes of unknown affinity and putative calcareous algae. Many of the genes and the proteins they encode are found to be conserved across geologic time from the Precambrian, especially those involved in the most basic cellular functions.