Direct dating of human fossils
Geosciences /2/04 Direct-dating of fossils Absolute (calendar) age vs relative age Direct dates vs associated dates Methods for direct-dating 1. Dendrochronology and sclerochronology Individual fossils and cross-dating 2.Radiocarbon dating Radiocarbon incorporated into living material Exponential decay and half-lives Two key assumptions: (1) near-constant production rate and (2) rapid mixing Correcting for the assumptions: (1) tree-ring calibration and (2) reservoir ages Two applications: constructing a sea level curve and dating the Shroud of Turin 3.Many more transitional fossils have been discovered since then, and there is now abundant evidence of how all classes of vertebrates are related, including many transitional fossils.Specific examples of class-level transitions are: tetrapods and fish, birds and dinosaurs, and mammals and "mammal-like reptiles".
Skeletal tissues can, in principle, be dated with an open-system U-series approach, which requires that the Th/U activity ratio is still below equilibrium.
Growth rings: in wood (=dendrochronology) or accretionary skeleltons (coral, or mollusks) (=sclerochronology).
Trees in seasonal climates add wood during the summer and slow or stop growth in the winter.
In 1859, when Charles Darwin's On the Origin of Species was first published, the fossil record was poorly known.
Darwin described the perceived lack of transitional fossils as, "..most obvious and gravest objection which can be urged against my theory," but explained it by relating it to the extreme imperfection of the geological record.