One of Earth’s most remarkable attributes is the permanent oxygen component of the planet’s atmosphere. Oxygen’s reactivity makes it an efficient energy source for life, but it also means oxygen would disappear quickly without a continuous resupply. Atmospheric oxygen increased dramatically during two different periods in Earth’s history. Yet these increases occurred only because of a complex and elegant interplay of geological, astronomical, biological, atmospheric, and chemical processes.
For most of Earth’s history its atmosphere contained no oxygen. Then, just over two billion years ago, oxygen gained a permanent foothold, though at a fraction of today’s concentrations. Even greater jumps in oxygen content occurred between 600 and 800 million years ago. These jumps resulted in long-standing consequences. First, they were often accompanied by intense ice ages where glaciers advanced close to the equator. Scientists believe these aptly-named “snowball Earth” events may have occurred because increased oxygen levels converted methane, a strong atmospheric greenhouse gas, into the less potent carbon dioxide. As catastrophic as these snowball events were, the changes in Earth’s atmosphere were necessary to compensate for the Sun’s steadily increasing luminosity. Fortunately, aspects of biological activity prevented the glaciations from destroying Earth’s capacity to support life.
Most importantly, the oxygen jumps ushered in a dramatic rise in life’s complexity. Previous research indicated that changes in the plate tectonic activity—specifically the first formation of tall mountains—increased the supply of molybdenum to the oceans and that, in turn, boosted biological activity.
Now it appears that the changes in biological activity (both the increase in number and complexity) also required a boosted phosphorous supply. According to research recently published in Astrobiology, phosphorite deposits across the globe correspond to Earth’s two great oxygenation events.1 The model outlined in the paper argues that tectonic processes produced a greater (and higher) continental landmass. The weathering of this landmass transported phosphorous to the oceans, causing a dramatic rise in primary biological production. After the last increase in oxygen around 650 million years ago Earth could finally support complex, multicellular organisms.
We at RTB argue that any mechanism exhibiting complex, integrated actions that bring about a specified outcome is designed. Studies of Earth’s history reveal highly orchestrated interplay between astronomical, geological, biological, atmospheric, and chemical processes that transform the planet from an uninhabitable wasteland to a place teeming with advanced life. The implications of design are overwhelming.
- Dominic Papineau, “Global Biogeochemical Changes at Both Ends of the Proterozoic: Insights from Phosphorites,” Astrobiology 10 (April 19, 2010): 165–81.