will be used as mean age.
The standard deviation can be provided. # still need to add this option.
By default, a 95 CI sd is used.</p></dd>

<dt>uniform</dt>
<dd><p>The age given in ncalibration will be used as mean age.
Where min_age = 0.9 * mean age, and max_age = 1.1 * mean age.</p></dd>


</dl></dd>


<dt>root_calibration</dt>
<dd><p>Used to set a calibration at the root or not. Default
to FALSE. Only relevant if ncalibration is specified.</p></dd>


<dt>mrbayes_constraints_file</dt>
<dd><p>NULL or a ch