A sharp increase in the amount of oxygen in the air may have sparked the evolution of complex animal life. Chemical analysis of 580-million-year-old rock sediment shows oxygen levels in the deep ocean surged upwards just before large creatures appeared on the sea floor.
Researchers have long thought that the emergence of complex life forms — strange creatures called Ediacarans — was likely sparked by an increase in oxygen that such animals would need to live. But proof of this theory has been scant.
Two papers, published by Nature and Science this week, both conclude that oxygen levels at this time did indeed shoot upwards in the deep seas. The air at that time, it now seems, probably had about 15% of today's oxygen levels.
Looks like I'll be spending some time in the library tomorrow reading those articles. Here's another PR about the article published in Science (via PALEOBLOG).