This is a fork of TreeSim with an additional function, sim.rateshift.age, which can be used to generate phylogenies under piecewise constant birth and death rates with a fixed origin age.
Currently, TreeSim includes sim.rateshift.taxa, sim.bd.age and sim.bd.taxa functions. Our new functions combines the piecewise constant birth and death rate support of sim.rateshift.taxa with origin age conditioning, as in sim.bd.age.