Ah, I see, so now you are claiming that the appearance of a second air connection to the lung is a "binary change" and thus impossible. I disagree. Without knowing the layout of the bronchi and lungs in these early creatures, it seems to me illogical to say it is impossible, any more than a hole in the heart is "impossible" - when in fact it is very common. As for the asymmetric tidal flow which I am suggesting as a half way house, it is clear you still either can't understand it or else are determined to make artificial difficulties for some reason. I do not have the patience to spend more time on this with you. As I say, I'm grateful to Trippy and others for an enlightening discussion.