MISTAKEN POINT, N.L. – Researchers in Newfoundland and Labrador say they may have have unlocked a 575-million-year-old “enigma” embedded in the sea floor at the southeast tip of the Avalon Peninsula.
The fossils at Mistaken Point, so named for its disorienting fog, are some of the oldest-known evidence of early multicellular creatures as well as one of paleontology’s great mysteries.
Scientists have long speculated about the fossils known as the Ediacara biota, primarily, about what kind of life they were. The ancient sea creatures have been labelled everything from giant single-celled organisms, fungi, relatives of the jellyfish and even an extinct evoluntarily experiment that was neither plant nor animal.
Two professors at Newfoundland and Labrador’s Memorial University have proposed a new explanation for this evolutionary riddle, and in doing so, may reinvorogate a debate about what the scientific definition of an animal is.
“People have been looking at modern organisms and comparing these weird, sort of fractal Ediacaran things,” paleontologist Dr. Duncan McIlroy said in a phone interview. “What we tried to do was imagine life as an Ediacaran organism.”
In a paper published by The Geological Society of the U.K., McIlroy and Dr. Suzanne Dufour, a biologist at the university, took a new approach to interpreting the fossils, tubular, mostly immobile organisms that could reach one metre in length.
They considered the challenges this organism may have faced and have concluded the fossils should be classified as animal.
“We know they were lying flat on the seafloor. They weren’t moving around much,” Dufour said in a phone interview. “One of the problems with that mode of life is that sulfide builds up underneath them … If that’s something that’s toxic to you, then you’re kind of in trouble.”
Dufour says modern clams solve this problem by “teaming up” with bacteria. Ediacaran organisms may have had similar symbiotic relationships, she says. The bacteria would have used oxygen and the toxic hydrogen sulfide as a source of energy, which would detoxify the waters around the organism and allow it to survive.
“Animals have evolved in a world where bacteria were really dominant. They’d already been on this planet for millions of years before animals started to evolve,” says Dufour. “It makes sense that they would find ways to interact with them and get some benefits from them … And that’s how I think animals really got their start.”
McIlory anticipates treating the fossils as animals could foster some debate in scientific circles about what it means to be an animal. According to some definitions, an organism has to move for it to be an animal, but McIlroy contends that this is an anachronistic view.
“If you a biologist in the Ediacaran (era), what would you call an animal?” he says. “We tend to look at it from a modern perspective and we say, ‘They all move.’ … We would say an animal doesn’t need to move, but some people may be unwilling to let go of that concept.”
Mistaken Point has been declared a world heritage site by the United Nations Organization for Education, Science and Culture.