Scientists recently discovered that air flows through monitor lizards' lungs in one direction; this pattern of breathing may prompt a change in the way people think about how some species evolved following the Earth's biggest mass extinction, Agence France-Presse reported.
A new study found that the pattern of taking in air that flows through lungs in a one-way loop may have originated 270 million years ago in the" ancestral group that gave rise to dinosaurs, and eventually alligators and birds, according to Discovery News.
After examining the airflow of living and deceased monitor lizards - which can be found through Africa, China, India and other parts of Southeast Asia - researchers at the University of Utah, in Salt Lake City, and Harvard University, in Cambridge, Mass., found evidence that suggest that one-way airflow breathing may have evolved "earlier than scientists thought."
The large, carnivorous reptiles breathes, the airflow through their lungs is mostly one-way, unlike in humans and other mammals, which have a "tidal," or two-way, breathing pattern.
"Human lungs consist of a network of tubes that branch out into progressively smaller airways. Tidal breathing means air enters the lungs through these airways and then flows back out again the same way," Discovery News reported.
This unusual pattern of breathing has raised much debate among biologists.
The unidirectional airflow in birds was first suggested in the 1930s, Colleen Farmer, an associate professor of biology at the University of Utah and senior author of the new study, told LiveScience
"It was first noted in birds that were living in train stations in Europe," Farmer said. "They were burning coal to power trains and noticed that only one part of the bird's lung was getting black with soot."
Farmer said the discovery of one-way airflow in monitor lizards indicates the breathing method may have evolved even earlier -- about 270 million years ago -- among cold-blooded diapsids, which were the common, cold-blooded ancestors of present-day lizards and snakes.
Farmer published a study in 2010 that detailed similar unidirectional airflow in alligators "which suggests the breathing pattern likely evolved about 250 million years ago, when the ancestors of alligators and crocodiles split from the ancient archosaurs, the group that led to the evolution of dinosaurs, flying pterosaurs and eventually birds," Discovery News reported.
This one-way airflow method of breathing was thought to have evolved in birds "to help them extract higher amounts of oxygen from their environment," Discovery News reported. The logic applied was that since air travels in only one direction through birds' lungs, "more oxygen is transferred through their respiratory systems with each breath, which enables them to fly at high altitudes, where oxygen levels are low, without getting winded or passing out."
It was also speculated that one-way airflow may have helped the ancestors of dinosaurs roam the Earth beginning roughly 251 million years ago after the Permian-Triassic mass extinction which wiped out about 70 percent of terrestrial vertebrate species.
