What's the secret to the evolution of complex life on Earth? The answer might surprise you.

International team of scientists discovered that shifts in phosphorus cycle are responsible for evolution of life on Earth

Katie Willis - 05 January 2017

Approximately 750 million years ago, a fundamental change occurred that set the stage for the evolution of life on Earth as we know it-phosphorus in ocean shallows.

A lack of phosphorus, a critical nutrient for many modern systems, prevented the evolution of complex life for nearly 3.5 billion years. A dramatic rise in phosphorus concentrations in the Neoproterozoic lead to the oxygenation of Earth and the evolution of complex, multicellular life.

"These findings are critical for understanding the long-standing dilemma of why it took animals so long to evolve," explains Kurt Konhauser, professor in the University of Alberta's Department of Earth and Atmospheric Sciences.

International collaboration

In conjunction with an international team, Konhauser and PhD student and Vanier scholar Leslie Robbins examined a dataset of more than 15,000 geochemical analyses of shales.

Before the Neoproterozoic period, low levels of phosphorus buried in shales suggest that marine cyanobacteria were hampered by its limited availability, potentially explaining the delay in oxygenation of Earth's atmosphere.

The lack of phosphorus highlighted by this new record indicates that primitive microbial life did not extract nutrients at the same rate as their modern counterparts. For instance, low levels of phosphorus may have led primary producers to increase their carbon to phosphorus ratios relative to modern microbial communities.

"If cyanobacteria were simply starved until 800 million years ago, then Earth could never have accumulated sufficient oxygen for animals to evolve. The change in phosphorus cycle may have resulted in life on Earth as we know it."

The paper, "The Evolution of Earth's Phosphorus Cycle," was published in Nature.

"These findings are critical for understanding the long-standing dilemma of why it took animals so long to evolve." -Kurt Konhauser