It took an awful lot of clever adaptations to the produce common bird. It’s got to be light, so you give it hollow bones. It’s got to be strong, so you give it less a breastbone than a keel, to which powerful wing muscles can be attached. And it’s got to have a prodigious respiratory system—flying ain’t easy—so you give it a peculiar system of multiple air sacs serve as lungs, with the air rushing through in one direction, making a tour of each of the chambers and then exiting, rather than rushing in and out, as in our lungs.
Now, a new study in Nature suggests that something else is at work in those lungs: avian respiratory architecture may be a feature left over from the long-ago days when birds were dinosaurs. That conclusion was announced by a group of scientists from the University of Utah, who did their work not by studying birds, but their distant cousins, monitor lizards. Earlier evidence had already shown that alligators have a four-chambered respiratory system, so it was no news that monitor lizards do too. But the researchers were less interested in what the architecture of the animals’ lungs is than in how the whole system works.
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