Researchers have discovered new fossils in Namibia that support the idea that the first mass extinction in the world was caused by early animals or "ecosystem engineers," newly evolved biological organisms that changed the environment so drastically that older species were wiped out.
Called the end-Ediacaran extinction, the event took place some 540 million years ago when single-celled organisms, the most successful of which were the Ediacarans, were pushed into extinction by newer species coming into the scene and evolving.
These newer species were called metazoans, the first animals. They could move independently and spontaneously, at least at some point in their lives, and sustained themselves by consuming other organisms or eating what other organisms have produced. The moment they burst onto the scene is known as the Cambrian explosion, the 25-million-year period where most of the modern animals known today started living on the planet.
According to Simon Darroch and colleagues, the fossils they discovered were some of the best-preserved examples of a community housing both Ediacarans and the early animals, providing evidence of close ecological interaction between the two.
Before this, there was limited evidence showing an overlap between Ediacarans and metazoans.
In an earlier study, the researchers reported on a fossil record showing stressed-looking communities of Ediacara associated with a number of animal burrows.
The newly discovered ones come after that, offering a snapshot of an unusual transitional ecosystem that was in place before the Cambrian explosion, highlighting Ediacarans' last-ditch efforts to cling on to life.
According to Darroch, their discovery has a relevant message. With people as the most powerful ecosystem engineers of today, the evolution of their new behaviors has repercussions for the whole planet.
Published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology, their study received funding support from the National Science Foundation, the NASA Astrobiology Institute and the National Geographic Society. Thomas Boag, Rachel Racicot, Douglas Erwin, Sarah Tweedt, Marc Laflamme and Sara Mason also contributed to the research.
Another theory blames a mass extinction 2.59 million years ago on a supernova explosion that occurred hundreds of light-years away from Earth. According to researchers, the exploding star resulted in rapid-moving cosmic rays to be blasted out, which led to a die-off as the Pliocene era ended and the Pleistocene era began.
"It's controversial. But maybe cosmic rays had something to do with it," said Adrian Melott, an expert from the University of Kansas and co-author of a study published in the Astrophysical Journal Letters.
