Low levels of oxygen may have hindered evolution of diverse life-forms
The diversification of early animals may have been suffocated by a lack of oxygen. A new analysis of ancient rocks offers a glimpse of conditions in the millions of years leading up to the proliferation of animals. The data suggest that oxygen levels were less than 1 percent of today’s levels, low enough that they may have stalled the emergence of animal life.
Scientists have been puzzled by a prominent lag in life’s evolutionary timeline. Around 2.3 billion years ago, cyanobacteria were producing such quantities of oxygen that scientists refer to that time as the Great Oxygenation Event. But then things got pretty quiet and Earth entered a period known as the boring billion. It wasn’t until some 800 million years ago that proper multicellular animals started to appear on the scene (SN: 12/31/11, p. 12).
Researchers have been unclear about the role of environmental factors in this delay,