I would appreciate knowing why you find it implausible. Since the issue is related to transmission of original sin I would like to suggest you post the reasons in this other thread.
Nonetheless I think it would be also fitting posting here since in the end the question at the core of the debate seems to be:
Is it theologically necessary that all Image Bearers are genetically or at least genealogically descended from a single couple?
I would be thankful to know your answer to this question.