A few billions of years ago, an extinction took place that undersized the event in which dinosaurs have disappeared, about 65 million years ago. Its impacts were found in Canadian rocks, which show that Earth has lost about 75 percent of its plant and animal life.
However, that particular event allegedly had a benefit for us as the kill rate of microorganisms that formed the planet’s atmosphere made way for larger animals to thrive. It might seem that microbes cannot be stopped when considering the current pandemic, as well as the other infectious diseases we know of, but even when biology on Earth was composed of microbes in its entirely, they still had die-off events.
Life Before Complex Life
Due to the fact that this period proceeded complex life, fossils can help researchers understand what existed two billion years ago, but analyzing clues left in mud and rocks is a rather difficult process to uncover.
Therefore, for a new study, a group of researchers collected barite, a mineral they found in the Belcher Islands of Hudson Bay, Canada, that comprises a record of oxygen in the atmosphere. The samples unveiled the fact that Earth faced massive changes to its biosphere, ending with a gigantic drop in life about 2.05 billion years ago and may have also be associated with decreasing oxygen levels.
“The size of the biosphere through geologic time has always been one of our biggest questions in studying the history of the Earth,” said Erik Sperling, an assistant professor of geological sciences at Stanford University who was not involved in the research. “This new proxy demonstrates how interlinked the biosphere and levels of oxygen and carbon dioxide in the atmosphere are.”
The Findings Support the Oxygen Overshoot Theory
This correlation between the expansion of life and atmospheric oxygen has provided scientists with new evidence of the theorized ‘oxygen overshoot.’ As per this theory, photosynthesis from ancient microorganisms and the erosion of rocks formed a massive amount of oxygen in the atmosphere that later declined as oxygen-producing organisms spent their nutrient resources in the ocean and became less abundant.
The team’s calculations of oxygen, sulfur, and barium isotopes in the sample of the mineral back up this oxygen overshoot theory and helps close down the size of the oxygen overshoot by unveiling the important biological impacts of oxygen levels above and below the ability of Earth.
“Some of these oxygen estimates likely require too many microorganisms living in the ocean in Earth’s past,” said co-lead author Peter Crockford, a postdoctoral researcher at the Weizmann Institute of Science and Princeton University. “So, we can now start to narrow in on what the composition of the atmosphere could have been through this biological angle.”