Having spent several cumulative party-hours explaining transmissible cancers to everyone involved, I am contractually obligated to point out that there are in fact _three_ mammals that have achieved immortality: one dog and _two_ tasmanian devils!
There are two lineages of DFTD: DFT1, which arose from a female devil, and DFT2, which arose from a male devil. https://www.cell.com/cancer-cell/fulltext/S1535-6108(18)30117-X
(There are also all the immortalized cell lines we have in labs, but none of those would be viable in the wild afaik)
Having spent several cumulative party-hours explaining transmissible cancers to everyone involved, I am contractually obligated to point out that there are in fact _three_ mammals that have achieved immortality: one dog and _two_ tasmanian devils!
There are two lineages of DFTD: DFT1, which arose from a female devil, and DFT2, which arose from a male devil. https://www.cell.com/cancer-cell/fulltext/S1535-6108(18)30117-X
(There are also all the immortalized cell lines we have in labs, but none of those would be viable in the wild afaik)