The Ancestor:

M. prototuberculosis

 

Some scientists believe that a group known as the Mycobacterium tuberculosis complex (MTBC), to which M. bovis belongs, descended from a pool of ancestral bacteria which has been termed M. prototuberculosis.  This ancestral pool includes a group known as the smooth TB.  They are known as a smooth group due to their glistening rounded appearance when allowed to grow on cultured media.  It is believed since some of the oldest MTBC strains cause human disease that the ancestral bacteria most likely caused disease in humans.