Today, the Earth's atmosphere contains 21% oxygen, however, this has not always been the case. Throughout our planet's history, fluctuations in the Earth's atmosphere have both influence and been influenced by biological life. About 280 million years ago, oxygen levels peaked at 30-35%, which correlates with an explosion in the diversity and radiation of tetrapods (four-legged animals) in the fossil record. Graham et al. 1995 hypothesized that increased oxygen availability in the atmosphere may have enhanced early tetrapod activity on land and aided in their expansion.
This study set out to test this hypothesis by using mudskippers, an amphibious fish, to model the effects of oxygen on the terrestrial performance on early land vertebrates. These fish were exercised on a treadmill under different oxygen levels that mimicked those that occured during the Paleozoic.
With increased oxygen, mudskippers were able to both run longer and recover faster from exercise. These findings suggest that early tetrapods also likely benefited from elevated oxygen levels during the Permian. Increased aerobic performance may have enhanced ability to capture prey and avoid predators, and ultimately aid in the survival and establishment of tetrapods beyond the waters edge.
This work has resulted in the following publication and cover: