New study shows evidence of oldest mass extinction on planet Earth

The history of life on Earth has always been full of phenomena that challenged the evolution of species and put all existing ones at risk.

These catastrophic events were caused by a variety of factors, and only five mass extinctions are known to have occurred. At least, that’s what scientists believed until this new discovery.

This is because a recent study managed to gather evidence about a possible sixth mass extinction event. In fact, it would be the first of them all.

Furthermore, it appears to have occurred even before the Cambrian explosion, which occurred about 538 million years ago.

The first extinction in Earth’s history

Virginia Tech paleontologist Scott Evans and his colleagues last year published data indicating a mass extinction that occurred about 550 million years ago, in the Ediacaran period.

They used data obtained by studying rare fossils from that period and saw that the decrease in biodiversity already detected was not just caused by bias.

Arguments supporting the observations

Much of the marine life of this period was composed of soft-bodied animals. These soft parts do not fossilize easily, so it was easy to conclude that the lack of soft-bodied animals after the geological period was due to the difficulty in preserving fossils.

However, researchers observed an increase in biodiversity, a change in diet and lifestyle between two stages of the Ediacaran, the Avalon stage (575 to 560 million years ago) and the White Sea stage (560 to 550 million years ago).

Some mobile animals emerged during this period. Previously, only sessile animals, which remained fixed to the ground, were known. Between the White Sea stage and the end of the Ediacaran, with the Nama stage (550 to 539 million years ago), 80% of the species disappeared.

Of the 70 groups known in the intermediate phase, only 14 were observed in the last period, with losses in lifestyle and eating habits.

Scientists ruled out the replacement of beings by more evolved predators due to a lack of temporal overlap between species. The team explains:

“The decline in diversity among these assemblages is indicative of an extinction event, with the percentage of genera lost comparable to that experienced by marine invertebrates during the Big 5 mass extinctions.”

The animals that survived this extinction were large. In addition, they had a surface area capable of adapting to the decrease in oxygen present in the sea. With a larger contact area, it was easier to find the resource necessary for life at that time: oxygen.

Previous studies support current evidence showing a link between biotic turnover and environmental change and this mass extinction, as these changes have occurred in other records of these major events.