The theory that cancer cells themselves could be an infective agent (the Allograft Theory[18]) was first supported by the researchers A-M. Pearse, K. Swift, and colleagues. In 2006, Pearse and Swift analyzed DFTD cells from several devils in different locations, and determined that all of the DFTD cells were not only genetically identical to each other, but also genetically distinct from their hosts, and from all known Tasmanian devils.