Mammals are believed to have evolved from reptilian ancestors. The study suggests that the evolution of increased, sustainable aerobic capacity in animals required the development of muscles that could power the lungs to move air in and out quickly, independently of whether an animal was running. Studies of the locomotor and ventilatory systems of lizards also are important in providing a framework for ultimately understanding how humans breathe and the primary functions of human trunk muscles. Tomasz Owerkowicz, a graduate student at Harvard University, and Beth Brainard, an assistant professor at the University of Massachusetts, observed that monitor lizards were pumping air through their throats. They came to UCI to better understand how the pumping contributes to breathing, and turned to James Hicks, UCI professor of ecology and evolutionary biology , and UCI postdoctoral fellow Colleen Farmer for help.
Lizards scamper ahead by twisting their bodies from side to side as they move their feet forward.
Muscles in a lizard's trunk make it possible to move forward this way. Those same muscles also control how a lizard rotates its ribs and expands its lungs to breathe. So, most lizards cannot run far without getting out of breath. After a burst of speed, they must rest to recover the normal level of oxygen in their blood. But monitor lizards can run quickly and for some distance, and their blood oxygen levels remain high and constant while they're moving.