Tuberculosis (TB) remains one of the deadliest infectious diseases in human history, persisting even in the 21st century. The causative agent is a group of closely related bacteria in the Mycobacterium tuberculosis complex (MTBC), which includes human- and animal-adapted strains. These strains likely evolved from a common ancestor through clonal expansion and recombination. Understanding the evolution of MTBC may lead to improved TB control strategies and insights into future epidemiology. This review highlights new insights into mycobacterial evolution, focusing on genomic events that enabled the emergence and dominance of MTBC. It also reviews recent literature on MTBC lineages, their host preferences, and geographic distribution. The review discusses mechanisms driving the evolution of tubercle bacilli, using mycobacteria-specific distributive conjugal transfer as an example. The first mycobacterial genome sequence, of M. tuberculosis H37Rv, was published in 1998 and had a significant impact on understanding TB evolution. Subsequent studies revealed genomic diversity among mycobacterial species, leading to a reclassification of the genus Mycobacterium into five new genera. However, this reclassification was controversial, and the traditional single-genus nomenclature is preferred here. The MTBC includes strains that are closely related to M. canettii, which is thought to be a closely related outgroup. Despite genomic similarities, M. canettii and MTBC strains differ in host preferences and other traits. The evolution of tubercle bacilli at the genus level was influenced by gene gain via horizontal gene transfer (HGT) and gene loss. The genome of M. tuberculosis is smaller than that of environmental mycobacteria, suggesting adaptation to specific environments. The MTBC emerged from an M. canettii-like ancestor through various adaptations, including mutations and gene deletions. Key events in MTBC evolution include the deletion of the cobF gene locus, which is involved in vitamin B12 synthesis. The MTBC consists of nine human-adapted lineages and various animal-adapted strains, with some lineages showing a closer relationship to M. canettii. The phylogenetic position of animal-adapted MTBC strains was revealed by the deletion of specific genomic regions, such as RD9, RD7, RD8, and RD10. These deletions are not present in M. canettii or M. tuberculosis strains, suggesting that human-adapted M. tuberculosis strains did not evolve from animal-adapted M. bovis strains. The loss of the RD8 region may have been a key genetic event enabling the adaptation of MTBC strains to new mammalian hosts. The MTBC represents a clonal group of tubercle bacilli with diverse host adaptations, highlighting the complex evolutionary history of TB pathogens.Tuberculosis (TB) remains one of the deadliest infectious diseases in human history, persisting even in the 21st century. The causative agent is a group of closely related bacteria in the Mycobacterium tuberculosis complex (MTBC), which includes human- and animal-adapted strains. These strains likely evolved from a common ancestor through clonal expansion and recombination. Understanding the evolution of MTBC may lead to improved TB control strategies and insights into future epidemiology. This review highlights new insights into mycobacterial evolution, focusing on genomic events that enabled the emergence and dominance of MTBC. It also reviews recent literature on MTBC lineages, their host preferences, and geographic distribution. The review discusses mechanisms driving the evolution of tubercle bacilli, using mycobacteria-specific distributive conjugal transfer as an example. The first mycobacterial genome sequence, of M. tuberculosis H37Rv, was published in 1998 and had a significant impact on understanding TB evolution. Subsequent studies revealed genomic diversity among mycobacterial species, leading to a reclassification of the genus Mycobacterium into five new genera. However, this reclassification was controversial, and the traditional single-genus nomenclature is preferred here. The MTBC includes strains that are closely related to M. canettii, which is thought to be a closely related outgroup. Despite genomic similarities, M. canettii and MTBC strains differ in host preferences and other traits. The evolution of tubercle bacilli at the genus level was influenced by gene gain via horizontal gene transfer (HGT) and gene loss. The genome of M. tuberculosis is smaller than that of environmental mycobacteria, suggesting adaptation to specific environments. The MTBC emerged from an M. canettii-like ancestor through various adaptations, including mutations and gene deletions. Key events in MTBC evolution include the deletion of the cobF gene locus, which is involved in vitamin B12 synthesis. The MTBC consists of nine human-adapted lineages and various animal-adapted strains, with some lineages showing a closer relationship to M. canettii. The phylogenetic position of animal-adapted MTBC strains was revealed by the deletion of specific genomic regions, such as RD9, RD7, RD8, and RD10. These deletions are not present in M. canettii or M. tuberculosis strains, suggesting that human-adapted M. tuberculosis strains did not evolve from animal-adapted M. bovis strains. The loss of the RD8 region may have been a key genetic event enabling the adaptation of MTBC strains to new mammalian hosts. The MTBC represents a clonal group of tubercle bacilli with diverse host adaptations, highlighting the complex evolutionary history of TB pathogens.