Tassie devil facial tumour is a transmissible tumour - counter argument

The counter argument by Greg Woods is also on The Conversation. Online at:https://theconversation.com/tassie-devil-facial-tumour-is-a-transmissible-cancer-34312

I don't have a theory for the cause of the Tasmanian devil cancers, there are also mammary cancers and lymphosarcomas. I would like to see all hypotheses tested by rigous scientific methods.