'Pitbulls' have only existed as such since the very late 1800s. tool.
Like many modern breeds, it is impossible to be completely sure of the details of the American Pit Bull Terrier's long history. However, many pit bull enthusiasts believe the origins of the breed can be traced back to antiquity and the Molossian family of dogs. The Molossian family of dogs bears the name of the people with whom they were most often associated - the Molossi tribe, a group of people who lived in ancient Greece and favored the use of robust, muscular dogs in warfare.
When the Roman emperor Claudius defeated the Briton Chief Caractacus in 50 AD, the powerful pugnaces piqued his interest. He quickly seized on the opportunity and began exporting select quantities of the dogs back home to satiate his countrymen's appetite for entertainment in the arenas and coliseums of Rome.
Once in Rome, the British dogs were crossbred with their Roman counterparts. From the years 50 AD to 410 AD, the breed was widely disseminated throughout the Roman Empire for use as fighting dogs. Along the way they mixed with other indigenous breeds throughout Europe, creating a genetic melting pot for the bulldogs that are thought to have been the immediate antecedents of the American Pit Bull Terrier.
The above information is from a pro-pit bull website by the way!