Prehistoric Atmospheric Oxygen Levels

Every part of human life experiences ups and downs. The stock market goes up and down just like my energy levels. As it turns out, the amount of life on Earth experiences similar changes.

In fact, scientists have identified five large mass extinction events where a large fraction of life on Earth died. The largest extinction (known as the Permian—Triassic catastrophe) occurred roughly 250 million years ago. “It eradicated almost 95% of all species, 53% of marine families, 84% of marine genera, and approximately 70% of all land species including plants, insects and vertebrate animals.”

Although many models exist to explain the various mass extinctions, some scientists posit that a dramatic decrease in oxygen (either atmospheric or oceanic) caused some extinctions-particularly the Permian—Triassic and the Triassic—Jurassic event nearly 200 million years ago. A pair of Irish scientists developed a novel way to test this low-oxygen model. Throughout the fossil record dating back before 250 million years ago, scientists find evidence of wildfires. These wildfires require a minimum level of oxygen in the atmosphere.

Under carefully controlled environmental conditions, the scientists determined the lowest value for atmospheric oxygen that would have permitted wildfires. Their results indicate that over the last 250 million years, the level of oxygen in the atmosphere remained above 15% (for comparison, oxygen comprises 20.9% of the atmosphere today). Thus, the existence of fossil remains from wildfires argues against the low-oxygen models of extinction causes.

From an apologetic perspective, the causes of extinction events are not particularly important. However, as scientists better understand the course Earth followed from its “formless and void” state to its current highly diverse and populated state, more evidence for fine-tuning and design becomes apparent. RTB expects investigations into the causes of mass extinctions to continue that trend.