You don't say it, but your objection seems to be based on the premise that different species can't interbreed. But they can, if they are closely related enough. The black duck is endangered partly because of interbreeding with mallards. Black ducks and mallard ducks are clearly different species. It seems there are some exceptions to that rule.
Species descend from other species.
But they can, if they are closely related enough. The black duck is endangered partly because of interbreeding with mallards. Black ducks and mallard ducks are clearly different species. It seems there are some exceptions to that rule.