Original: By using radiometric dating techniques, the volcanic tuffs and lavas, faunal correlation and magneto-stratigraphy, the strata in which the fossils were found were estimated to date between 6.1 and 5.8 million years ago, during the Miocene.
Simplified: Orrorin tugenensis which the fossils were found were estimated to date between 6.1 and 5.8 million years ago, during the Miocene.