The members of genus Treponeme, family Treponemataceae, and order Spirochaetales consist of Treponeme pallidum (first described in 1905), which causes syphilis and nonvenereal syphilis; Treponeme pertenue (first described in 1905), which is responsible for yaws; and Treponeme carateum (first described in 1938), which produces pinta. Or at least this is the way that most medical texts would have it. It may be, however, that the three pathogens in question are actually only one, for although they produce different pathological processes, the pathogens themselves are virtually indistinguishable under the microscope, and the diseases they cause respond to the same treatment. The origin of this infamous family and the relationship of its members to one another have been topics of considerable and very interesting debate since the 1970s, largely because such questions bear directly on the centuries-old debate of whether the Americans bestowed syphilis on the rest of the world.

Many agree that the treponemes probably evolved from microorganisms that originally parasitized decaying organic matter, and which later – perhaps hundreds of thousands of years ago – came to specialize in human hosts, but probably only after first parasitizing another animal host (Wood 1978). There is little disagreement that the first treponemes to parasitize humans did so by entering their bodies through traumatized skin and were subsequently passed on to other humans by skin-to-skin transmission. Real disagreement begins, however, over questions of where the first humans were infected, and the identity of the disease they were infected with.