Not until 1950 do paleontologists begin to find signs of life earlier than the large-sized fossils dated 600 mya. Suspecting that microbial life evolved before animals and plants, thoughtful researchers commence a search.
In South Africa, explorers find the Fig Tree Formation. A rare series of sediments and rock many tens of thousands of feet thick, the Formation contains some units of dense rock called chert, a smooth form of quartz. Although the chert appears barren, a microscopic search reveals signs of the kind of life that helped make stromatolites. Fossilized bacteria, including cyanobacteria, lie peacefully arranged in smooth layers within the rock. Some of the minute microfossils within this Formation constitute precious evidence of early life.