The paper presents a Bayesian Markov chain Monte Carlo (MCMC) method for inferring species trees from multilocus data. The method models intraspecific polymorphism and incomplete lineage sorting, coestimating multiple gene trees embedded in a shared species tree along with the effective population size of both extant and ancestral species. The authors demonstrate the efficacy of their method using simulated data and compare it to existing methods, showing that their method outperforms both in terms of species tree topology estimation and divergence time and population size estimation. The paper also discusses the importance of multiindividual data and the impact of sequence length on estimation accuracy. Additionally, it explores the effect of varying the number of sampled individuals per species and compares the performance of their method with that of the BEST method and the supermatrix (concatenation) method. The authors conclude by highlighting the potential of the multispecies coalescent model to unify molecular systematics and phylogeography.The paper presents a Bayesian Markov chain Monte Carlo (MCMC) method for inferring species trees from multilocus data. The method models intraspecific polymorphism and incomplete lineage sorting, coestimating multiple gene trees embedded in a shared species tree along with the effective population size of both extant and ancestral species. The authors demonstrate the efficacy of their method using simulated data and compare it to existing methods, showing that their method outperforms both in terms of species tree topology estimation and divergence time and population size estimation. The paper also discusses the importance of multiindividual data and the impact of sequence length on estimation accuracy. Additionally, it explores the effect of varying the number of sampled individuals per species and compares the performance of their method with that of the BEST method and the supermatrix (concatenation) method. The authors conclude by highlighting the potential of the multispecies coalescent model to unify molecular systematics and phylogeography.