For as long as there has been life — there has been death.
Earth’s diversity of animals spread over the planet a half billion years ago during the Cambrian explosion, when life as we know it took hold.
Five major extinctions have happened since then, caused by Ice Ages, climate change from volcanoes, and the asteroid that killed the dinosaurs.
Now, a group of scientists say they’ve discovered another extinction event that predates all of those, according to research published in the science journal PNAS. It happened about 560 million years ago and killed an astounding 80 percent of all species. Known as the Ediacaran, this strange period in Earth’s evolution saw mostly soft-bodied animals. Many of them looked like plant fronds stuck in the sea floor, or creatures with some kind of shells, Science Alert wrote.
But something big happened between the Ediacaran period’s middle stage, known as White Sea (560 to 550 million years ago), and the last stage, known as the Nama (550 to 540 million years ago).
All types of life were affected by this sudden shift, the new research argues. Of about 70 known groups of species from the fossil record of the period, only 14 survived the transition from White Sea to Nama.
“The decline in diversity between 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 paper said.
Weirdness in the fossil record
Scientists had seen some weirdness in the fossil record before this new paper. Sudden shifts in biodiversity often point to extinction events, but evidence of an earlier extinction has often been dismissed as mere sampling bias.
After all, we’re talking about soft-bodied animals that don’t fossilize too well. Earlier researchers simply assumed that the observed changes came from a lack of well-preserved evidence.
But for their research, Virginia Tech paleobiologist Scott Evans and his colleagues compiled lots of data on the Ediacaran period’s squishy animals. They found that the period’s surviving animals were typically large, frond-like organisms able to cope with a reduction in oceanic oxygen.
An artist rendering of Dickinsonia, a group of extinct creatures of the Ediacaran era, and one of the first animals. Photo: Shutterstock
That dovetails with 2018 research suggesting extensive anoxia of Earth’s oceans that covered more than 20 percent of the seafloor at the end of the Ediacaran.
This newly discovered extinction event will likely see plenty of debate before/if scientists agree enough to give it an official name.
In the meantime, much of modern Planet Earth seems more concerned with the Sixth Extinction happening right now — the one caused not by environmental changes, but by human destruction of our own environment.
