Dating techniques in geology
Early geologists, in the 1700s and 1800s, noticed how fossils seemed to occur in sequences: certain assemblages of fossils were always found below other assemblages. Since 1859, paleontologists, or fossil experts, have searched the world for fossils.
In the past 150 years they have not found any fossils that Darwin would not have expected.
Of all the isotopic dating methods in use today, the uranium-lead method is the oldest and, when done carefully, the most reliable.
Unlike any other method, uranium-lead has a natural cross-check built into it that shows when nature has tampered with the evidence.
Our understanding of the shape and pattern of the history of life depends on the accuracy of fossils and dating methods.