Contagious cancer: The evolution of a killer

The fact this can happen is that dogs only have around 13 blood types, where as humans have 26. The reason humans have 26 blood types is likely this exact problem, humans are a highly sexually active and stupid species, I mean look at the propogation of sexual infections in the UK even with free cures and free condoms (I'm not joking, you can get condoms for free and people don't use them!).

The significant thing in canines is that up to 45% of dogs are universal recipients. Basically the cancer has a 50/50 chance of finding a perfect host. No wonder DFTD is so lethal, in most cases the host body will just let the infection in.

However, it's lucky there isn't a feline varient of this disease as IIRC upto 80% of cats in North America are blood type A.