A key point is that it is no longer necessary simply to accept one chemical determination of a rock’s age.Age estimates can be cross-tested by using different isotope pairs.New discoveries have filled in the gaps, and shown us in unimaginable detail the shape of the great ‘tree of life’.Darwin and his contemporaries could never have imagined the improvements in resolution of stratigraphy that have come since 1859, nor guessed what fossils were to be found in the southern continents, nor predicted the huge increase in the number of amateur and professional paleontologists worldwide.These demonstrate that, of course, we do not know everything (and clearly never will), but we know enough.
Paleontologists now apply sophisticated mathematical techniques to assess the relative quality of particular fossil successions, as well as the entire fossil record.
The basic theory of radiometric dating is briefly reviewed.
Since 1955 the estimate for the age of the Earth has been based on the assumption that certain meteorite lead isotope ratios are equivalent to the primordial lead isotope ratios on Earth.
Our understanding of the shape and pattern of the history of life depends on the accuracy of fossils and dating methods.
Some critics, particularly religious fundamentalists, argue that neither fossils nor dating can be trusted, and that their interpretations are better.