From John MacDonald
When discussing the controversy over atmospheric oxygen levels during the age of the dinosaurs, Stephen Battersby asks: “Did the dinosaurs have to breathe heavily despite their efficient bird-like lungs?” (17 July, p 38).
A more interesting question is, what evolutionary imperatives resulted in the development of those efficient lungs, which were later important in the flight ability of birds? If oxygen was plentiful, as suggested by researcher Tim Lenton in the article, there would have been no need for highly efficient breathing systems. Robert Berner’s competing model of low oxygen levels seems far more likely, and might be supported by the steady increase in the size of flying dinosaurs before they became extinct: as the air became thinner, bigger wings would be needed for flight to be possible.
London, UK
