Original sentence: Also arguing for worldwide incidence of syphilis prior to Columbus' voyage, Douglas Owsley, a physical anthropologist at the Smithsonian Institution, suggests in an article with John Lobdell that many medieval European cases of leprosy, colloquially called lepra, were actually cases of syphilis.Historian Alfred Crosby suggests both theories are correct in a "combination theory".However, Crosby considers it more likely that a highly contagious ancestral species of the bacteria moved with early human ancestors across the land bridge of the Bering Straits many thousands of years ago without dying out in the original source population
Edited sentence: "  However, Crosby considers it more likely that a highly contagious ancestral species of the bacteria moved with early human ancestors across the land bridge of the Bering Straits many thousands of years ago without dying out in the original source population.Douglas Owsley, a physical anthropologist at the Smithsonian Institution, and other supporters of this idea say that many medieval European cases of leprosy, colloquially called lepra, were actually cases of syphilis.Finally, historian Alfred Crosby suggests both theories are partly correct in a "combination theory"