+ If two nodes are linked (i.e., one is the ancestor of the other) and
+ have the same values of \code{age.min} and \code{age.max} (say, 10 and
+ 15) this will result in an error because the medians of these values
+ are used as initial times (here 12.5) giving initial branch length(s)
+ equal to zero. The easiest way to solve this is to change slightly the
+ given values, for instance use \code{age.max = 14.9} for the youngest
+ node, or \code{age.max = 15.1} for the oldest one (or similarly for
+ \code{age.min}).
+