The exact origin of syphilis is unknown. Two primary theories have been proposed. It is generally agreed upon by historians and anthropologists that syphilis was present among the indigenous peoples of the Americas before Europeans traveled to and from the New World. However, whether strains of syphilis were present in the entire world for millennia, or if the disease was confined to the Americas in the pre-Columbian era, is debated.
The "Columbian Exchange theory" holds that syphilis was a New World disease brought back by Columbus and Martin Alonso Pinzon. Columbus's voyages to the Americas occurred three years before the Naples syphilis outbreak of 1494. This theory is supported by genetic studies of venereal syphilis and related bacteria, which found a disease intermediate between yaws and syphilis in Guyana, South America.
The "pre-Columbian theory" holds that syphilis was present in Europe before the discovery of the Americas by Europeans. Some scholars during the 18th and 19th centuries believed that the symptoms of syphilis in its tertiary form were described by Hippocrates in Classical Greece. There are other suspected syphilis findings for pre-contact Europe, including at a 13–14th century Augustinian friary in the northeastern English port of Kingston upon Hull. This city's maritime history, with its continual arrival of sailors from distant places, is thought to have been a key factor in the transmission of syphilis. Carbon-dated skeletons of monks who lived in the friary showed bone lesions that supporters say are typical of venereal syphilis, although this is disputed by critics of this theory. Skeletons in pre-Columbus Pompeii and Metaponto in Italy with damage similar to that caused by congenital syphilis have also been found, although the interpretation of this evidence has been disputed. 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. Although folklore claimed that syphilis was unknown in Europe until the return of the diseased sailors of the Columbian voyages, "syphilis probably cannot be "blamed"—as it often is—on any geographical area or specific race. The evidence suggests that the disease existed in both hemispheres from prehistoric times. It is only coincidental with the Columbus expeditions that the syphilis previously thought of as "lepra" flared into virulence at the end of the 15th century." Lobdell and Owsley wrote that a European writer who recorded an outbreak of "lepra" in 1303 was "clearly describing syphilis."
Historian Alfred Crosby suggests both theories are partly correct in a "combination theory". Crosby says that the bacterium that causes syphilis belongs to the same phylogenetic family as the bacteria that cause yaws and several other diseases. Despite the tradition of assigning the homeland of yaws to sub-Saharan Africa, Crosby notes that there is no unequivocal evidence of any related disease having been present in pre-Columbian Europe, Africa, or Asia. Crosby writes, "It is not impossible that the organisms causing treponematosis arrived from America in the 1490s...and evolved into both venereal and non-venereal syphilis and yaws." 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. He hypothesizes that "the differing ecological conditions produced different types of treponematosis and, in time, closely related but different diseases."