Study reveals cause of Earth’s first mass extinction

A global depletion of oxygen caused the planet’s first mass extinction about 550 million years ago, an event that killed 80% of the animals in existence at the time, according to a new study by geobiologists at Virginia Polytechnic Institute and State University, also known as Virginia Tech.

Oxygen depletion caused Earth’s first mass extinction

In the history of the Earth, five great mass extinctions are believed to have occurred that have marked the different geological periods: the Ordovician (443 million years ago), the Late Devonian (372 million years), the Permian (252 million years ago), the Triassic (201 million years ago) and the Cretaceous (66 million years), as stated by National Geographic. The results of the new study affirm that there was an event in the Ediatric period (between 635 million and 542 million years ago) that occurred before any other, which caused the death of most of the animals in existence at the time due to a lack of oxygen.

The research led by Scott Evans, a Virginia Tech paleobiologist, collected a large amount of data on strange fossils from the Ediatric age and found very abrupt changes in biodiversity, which they explain as a possible episode of unreported mass extinction so far.

“Our study shows that, as with all other mass extinctions in Earth’s past, this new, first mass extinction of animals was caused by major climate change -- another in a long list of cautionary tales demonstrating the dangers of our current climate crisis for animal life,” says Evans, in the study published in Proceedings of the National Academy of Sciences, a peer-reviewed journal of the National Academy of Sciences..

The cause of the drop in oxygen levels is not yet known.

“It could be any number and combination of volcanic eruptions, tectonic plate motion, an asteroid impact, etc., but what we see is that the animals that go extinct seem to be responding to decreased global oxygen availability,” explains Evans.

Climate change impacts

Researchers say that most mass extinctions have been caused by climate changes similar to the current one. The study "informs us about the long-term impact of current environmental changes on the biosphere," the Virginia Tech statement said. In fact, other Virginia Tech research showed that global warming is developing anoxia in the world's freshwaters, that is, the loss of oxygen availability and the decreased ability of freshwater to retain oxygen.

There is another element that reinforces the theory: most of the creatures that survived the first mass extinction were large organisms similar to ferns, which could indicate that they were adapting to a lower level of oxygen.

“Mass extinctions are well recognized as significant steps in the evolutionary trajectory of life on this planet,” the study included. “Particularly, we find support for decreased global oxygen availability as the mechanism responsible for this extinction. This suggests that abiotic controls have had significant impacts on diversity patterns throughout the more than 570 million-year history of animals on this planet.”