Commentaries on Viewpoint: Precedence and autocracy in breathing control COMMENT ON “PRECEDENCE AND AUTOCRACY IN BREATHING

TO THE EDITOR: I read the Viewpoint article by Haouzi (1) entitled “Precedence and autocracy in breathing control” with great interest. The author makes a strong and informative case for the complexity of the mechanisms involved in the control of breathing. But he makes conventional error of assuming that “it evolved by chance and necessity . . . shaping the structures and functions of the respiratory control system through the slow process of natural selection.” First, Natural Selection is a metaphor, not a mechanism. On the other hand, we have successfully deconvoluted the evolution of the mammalian lung from the fish swim bladder by tracing cellular-molecular changes determined by cell-cell interactions across developmental and phylogenetic space and time (4). We now know that the swim bladder of physostomous fish such as the Zebra Fish is the functional and molecular homolog of the lung (5). Focusing on the vertebrate water-land transition (WLT) that forced the evolution of amphibians, reptiles, mammals, and birds from fish (3), documented gene duplications occurred within specific physiologic contexts during this transition (3). It is known that the deflation of the swim bladder is controlled by sympathetic adrenergic neurons (2) and that the -adrenergic receptor is one of the genes that duplicated during the WLT; this cascade offers the opportunity to systematically deconvolute the origins and evolution of breathing control phylogenetically and ontogenetically through comparative developmental and phylogenetic functional genomics. By using this rational approach, the evolutionary complexity of control of breathing and that of all complex physiology is now comprehendible.