Syphilis is caused by Treponema pallidum, a motile spirochaete bacteria. It's flagella is wrapped around it's outer membrane which gives it the unique ability to spin. Once it senses a host cell, it spins itself and physically drills into the cell.
One possibility is that treponemal diseases emerged even earlier in Eurasia or Africa, and reached the Americas with the first humans to migrate there at least 15,000 years ago
Another is that the bacteria jumped to humans from an animal host, says Anne Stone, an archaeological geneticist at Arizona State University in Tempe who was not involved in the study. Primates and other animals, including rabbits, can be infected with T. pallidum, she notes. “There may be reservoirs we have to think about.”