I'm interested in exploring the bottleneck history of an endangered population whose genetics has been previously sampled using nuclear and mtDNA. However, this population has extremely low genetic diversity, with 2 haplotypes between 36 sampled individuals. I've been unable to find results using such samples alone through coalescent modeling (i.e. Bayesian Skyline) likely due to the homogeny. As a work-around to give models some diversity to work with, would it be possible to add samples of an outgroup population that's closely related to my study population (likely diverged ~1 million years ago or less) to find any meaningful bottleneck information?