Scientists analyzed microfossils from a rock in Australia about 3 5 billion years ago  Using a secondary ion mass spectrometer, they separated carbon-12 from carbon-13 in each microfossil and measured the ratio between the two  They found that the fossils contained a population of primitive organisms  As a result, they speculate that life appeared on Earth as early as 3
The C-13 / C-12 ratio of microfossils has the characteristics of biological and metabolic functions
5 billion years ago