These demonstrate that, of course, we do not know everything (and clearly never will), but we know enough.
Today, innovative techniques provide further confirmation and understanding of the history of life.
Older dates may change by a few million years up and down, but younger dates are stable.
Some critics, particularly religious fundamentalists, argue that neither fossils nor dating can be trusted, and that their interpretations are better.
The methods are all based on radioactive decay: The first radiometric dates, generated about 1920, showed that the Earth was hundreds of millions, or billions, of years old.
Since then, geologists have made many tens of thousands of radiometric age determinations, and they have refined the earlier estimates.
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.