Traditionally researchers built timelines of human prehistory based on fossils and artifacts, which can be directly dated with methods such as radiocarbon dating and Potassium-argon dating.However, these methods require ancient remains to have certain elements or preservation conditions, and that is not always the case.While total-evidence dating uses the morphological data from the fossil record and morphological and sequence data from extant taxa together to infer the tree and divergence times.The age of each fossil is assigned a prior distribution directly.Since the 1950s, geologists have used radioactive elements as natural "clocks" for determining numerical ages of certain types of rocks. "Forms" means the moment an igneous rock solidifies from magma, a sedimentary rock layer is deposited, or a rock heated by metamorphism cools off.It's this resetting process that gives us the ability to date rocks that formed at different times in earth history.This style lasted for two hundred years till around 1880, when huge imports of cheap mass-produced German and American clocks put an end to longcase manufacture for good.Only a few custom-built grandfather clocks were made after this date.
It would not be long before the weights and pendulum were enclosed altogether to stop the pendulum being knocked accidentally when walking past the clock.Several steps involve in Bayesian dating analysis, importantly including data partitioning, specifying evolutionary model, calibrating internal nodes or fossils, and setting priors for the tree and the molecular clock model. Hereby, I demonstrate the molecular clock dating functionalities in Mr Bayes 3.2 step by step, while focusing on total-evidence dating, using an example dataset truncated from the Hymenoptera data analyzed in Ronquist et al. There are two modern approaches on dating species divergence using molecular data: node dating (e.g., Yang and Rannala, 2006; Drummond et al., 2006) and total-evidence dating (e.g., Ronquist et al., 2012a; Zhang et al., 2016).
In a Bayesian framework, node dating calibrates one or several internal nodes of the tree, each with a prior distribution derived from the fossil record.
From now on the timekeeping of clocks improved by a huge amount using the longer pendulum and "anchor" escapement.