Explore the intricacies of coalescent theory in this 90-minute lecture from the Third Bangalore School on Population Genetics and Evolution. Delve into topics such as selection and coalescent, the ancestral selection graph, and the Moran model. Examine various types of selection, including balancing, positive directional, and purifying selection, and their effects on genetic diversity. Learn about methods for detecting selection, such as allele frequency distribution and haplotype sharing. Discuss the challenges in interpreting genetic data and the importance of robust statistical approaches. Investigate gene trees, species trees, and the pairwise sequentially Markovian coalescent model. Gain insights into the complexities of population genetics and its applications in evolutionary biology.