27The Mycobacterium tuberculosis complex lineage 4 (L4), also known as the "Euro-American" 28 lineage, is the most widely dispersed of the seven human adapted lineages. L4 is comprised of ten 29 sublineages including L4.4, which has a moderate global distribution and is the most common L4 30 sublineage in New Zealand. We have used a phylodynamics approach and a dataset of 236 global 31 M. tuberculosis genomes to trace the origins and dispersal of L4.4 strains in New Zealand that are 32 predominantly found in Māori and Pacific people. We identify an L4.4.1.1 sublineage clade of 33 European origin, likely French, that is prevalent in indigenous populations in both New Zealand and 34 Canada. Molecular dating suggests that expansion of European trade networks in the early 19th 35 century led to dispersal of this clade to the South Pacific. We also identify historical and social factors 36 within the region that have contributed to the local spread and expansion of these strains, including 37 recent Pacific migrations to New Zealand and the rapid urbanization of Māori in the 20th century. Our 38 results offer new insight into the dispersal of M. tuberculosis in the South Pacific region and provide 39 a striking example of the role of historical European migrations in the dispersal of M. tuberculosis. 40 41 Author Summary 42 Tuberculosis kills more people worldwide than any other infectious disease and indigenous 43 populations are disproportionately affected by the disease. Here, we have used a large global dataset 44 of Mycobacterium tuberculosis bacterial genomes to trace the historical origins of tuberculosis strains 45 in New Zealand that are most frequently found in Māori and Pacific people. These strains are locally 46 known as the 'Rangipo' and 'Otara' strains (both Māori place names) and belong to the 47 "Euro-American" lineage of M. tuberculosis. Via genome analysis, we find that these strains are 48 closely related to M. tuberculosis strains found in indigenous populations in Canada that have a 49 European origin. We used a molecular dating approach (a molecular clock) to infer the ages of these 50 strains and date divergence events. The timing we infer corresponds to the introduction of these strains 3 51 to Polynesia via expanding European trade networks in the South Pacific in the early 19th century and 52 suggests that the Otara strain has migrated to New Zealand from the Pacific Islands multiple times. 53 Our results provide insight into human social phenomena underlying the expansion and dispersal of 54 M. tuberculosis and reassert the important role of European colonial migrations in the global dispersal 55 of the M. tuberculosis Euro-American lineage. This work also highlights the pejorative and 56 stigmatizing mislabelling of the New Zealand strains with indigenous Māori place names, suggesting 57 that these strains should be renamed. 58 59 Introduction 60 Tuberculosis (TB) is caused by the bacterial pathogen Mycobacterium tuberculosis (Mtb) and 61 other members of the Mtb complex (MTBC). TB kills m...