Extreme climate change sped process.

• Position: Evolution

Evidence linking early animal evolution to extreme climate change has been uncovered by an international team of scientists. A dramatic rise in atmospheric oxygen levels long has been speculated as the trigger for early animal evolution, but direct evidence has proven elusive to scientists. However, a University of Nevada, Las Vegas-led research team for the first time offers evidence of a causal link between trends in early biological diversity and shifts in Earth system processes.

The fossil record shows a marked increase in animal and algae fossils roughly 635,000,000 years ago. An analysis of organic-rich rocks from Soufo China points to a sudden spike in oceanic oxygen levels at this time --in the wake of severe glaciation--allowing animal life to flourish. The new evidence pre-dates previous estimates of a life-sustaining oxygenation event by more than 50,000,000 years.

"For more than three-quarters of the Earth's history, the oxygen level in the atmosphere and ocean was insufficient to support animal life," points out lead author Swapan Sahoo, a Ph.D. student in the Geoscience Department. "Our findings support a link among glaciation, oxygenation of surface environments, and the diversification of animals. Knowing the environment where the first animals lived is critical for understanding the evolutionary stress of...