‘The origin of life’ hows that from the earliest days people have wondered about the origins of life. The discovery of radioactivity and radioactive decay of elements paved the way for radioactive dating of rocks and led to Arthur Holmes publishing the first age estimates of the earth in 1911. The debate of when the earth became habitable is discussed along with traces of early life and the biochemical theory for the origin of life, including the Oparin–Haldane model. The RNA world hypothesis is considered and shown to be a possible explanation for the very first living cells. The first fossils — microfossils and stromatolites are also described.