  The age of the root of the Indo-European language family has received much
attention since the application of Bayesian phylogenetic methods by Gray and
Atkinson(2003). The root age of the Indo-European family has tended to decrease
from an age that supported the Anatolian origin hypothesis to an age that
supports the Steppe origin hypothesis with the application of new models (Chang
et al., 2015). However, none of the published work in the Indo-European
phylogenetics studied the effect of tree priors on phylogenetic analyses of the
Indo-European family. In this paper, I intend to fill this gap by exploring the
effect of tree priors on different aspects of the Indo-European family's
phylogenetic inference. I apply three tree priors---Uniform, Fossilized
Birth-Death (FBD), and Coalescent---to five publicly available datasets of the
Indo-European language family. I evaluate the posterior distribution of the
trees from the Bayesian analysis using Bayes Factor, and find that there is
support for the Steppe origin hypothesis in the case of two tree priors. I
report the median and 95% highest posterior density (HPD) interval of the root
ages for all the three tree priors. A model comparison suggested that either
Uniform prior or FBD prior is more suitable than the Coalescent prior to the
datasets belonging to the Indo-European language family.
