Its causative agent

6.      The tropical skin disease called yaws is transmitted by direct contact.  Its causative agent, Treponemapallidumpertenue is indistinguishable from T. pallidum.  One theory is that syphilis epidemics in Europe coincided with the return of Columbus from the New World.  How might T. Pallidumpertenue have evolved into T. Pallidum in the temperate climate of Europe? (15 points)