Dinosaurs Lived in a Low-oxygen World, Study Suggests

Dinosaurs lived in a low-oxygen world, according to a new discovery that challenges a number of theories about the evolution of the Earth's climate and life.

Led by Ralf Tappert of the University of Innsbruck, scientists used 538 fossil plant resins, or amber, to reconstruct a 220-million-year history of the Earth's atmosphere.

"Compared to other organic matter, amber has the advantage that it remains chemically and isotopically almost unchanged over long periods of geological time," Tappert, from the Institute of Mineralogy and Petrography at the University of Innsbruck, explained in a statement.

The international team consisting of mineralogists, paleontologists and geochemists tested the validity of their data by examining modern resin as well.

Based on their results, they determined that for much of the Earth's history dating back to the Triassic Period, oxygen levels hovered between 10 and 15 percent -- far below today's 21 percent and the 30 percent previous studies suggested characterized the Cretaceous Period, which lasted between 65-145 million years ago.

"We found that particularly low oxygen levels coincided with intervals of elevated global temperatures and high carbon dioxide concentrations," Tappert said, adding that oxygen may affect the influx of CO2 into the atmosphere, perhaps even accelerating it under the right circumstances. "Basically, we are dealing here with simple oxidation reactions that are amplified particularly during intervals of high temperatures such as during the Cretaceous period."

Based on this, the scientists believe that a rise in CO2 levels due to high volcanic activity was paired with a drop in atmospheric oxygen, and that the relatively low temperatures of the more recent past, such as those experienced during the Ice Ages, may be due to a lack of volcanism and an increase in atmospheric oxygen.

Ultimately, the study directly contradicts the theory that high levels of atmospheric oxygen led to the animal gigantism seen in dinosaurs.

"We do not want to negate the influence of oxygen for the evolution of life in general with our study," Tappert said, "but the gigantism of dinosaurs cannot be explained by those theories."