  We consider a stochastic process for the generation of species which combines
a Yule process with a simple model for hybridization between pairs of
co-existent species. We assume that the origin of the process, when there was
one species, occurred at an unknown time in the past, and we condition the
process on producing n species via the Yule process and a single hybridization
event. We prove results about the distribution of the time of the hybridization
event. In particular we calculate a formula for all moments, and show that
under various conditions, the distribution tends to an exponential with rate
twice that of the birth rate for the Yule process.
