The currently prevailing theory of a transmissible cancer cell lineage in Tasmanian devils was based on the discovery of apparently identical chromosomal aberrations in facial tumors of several animals. New findings of facial tumors that have no detectable cytogenetic similarities to previously published cancer karyotypes and the recent detection of varying portions of chromosome Y in all tumor cell lines of male devils (but none in tumors of females) cast doubt on the theory of a cancer transplant. Thus, I propose an alternative scenario in which similar chromosomal and genetic aberrations in individual cancers are a consequence of the low genetic diversity in populations of the Tasmanian devil resulting in a unique telomere length profile. Critically short telomeres on certain chromosome ends lead to chromosome-specific fusions and the activation of species-specific transposable elements that cause the observed karyotypic and molecular convergence. This new concept can explain the existence of genetic signs of tumor clonality within a population despite the independent origin of each facial cancer in these cancer-prone animals.