The big news yesterday was, of course, the surprise announcement that most modern humans descended from ancient stock that left Africa early on are, in fact, 1%- 4% Neanderthal.*
So species inter-breeding is possible within the wider human family.
But I wouldn't expect to see even 4% of the Lib-Dem programme make the statute books if Clegg gets into bed with Cameron.
& we're still left with the mystery of why exactly the Neanderthals and modern humans couldn't co-exist in Europe....oh, hang on there's another analogy just forming in the back of my brain...
*As anyone who has ever watched an interview with Blackburn Rovers' manager already knew.