The latter two datasets were also much more informative than SNP, as half as many calibration data points were required to obtain a good model performance.
We include as many fossil calibration points as possible in disparate parts of the avian tree to maximize information from the fossil record, and reduce dependency on any one calibration estimate.
We used as many available calibration points as possible because this is the most accurate method to determine the rate variation across trees that include distantly related taxa [ 65].
*They used two distinct dating methods and many distinct calibration point settings.
Many of the calibration points used separately provide very young ages for the entire phylogeny, including ages for certain nodes that are even younger than the minimum age as established from the fossil record (Table 2).
In the absence of appropriate internal calibration points for many groups of birds, the 2% divergence-per-My clock calibration has been widely used.
Because of this potential bias, the uncertainty over calibration points and the many assumptions associated with molecular clock based dating, it is important to stress that the divergence times used in this analysis should be considered only as approximations.
However, calibration points can be extracted automatically from many scenes.
However, most of these studies have relied on a single or a few (often incorrectly applied) fossil calibration points that are often far removed from many of the nodes being dated.
This has important consequences for studies of conservation genetics, many of which have relied on substitution rates obtained by adopting relatively deep calibration points.
