A new theory about the ancient fossils at Mistaken Point

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 multi-cellularcreatures, as well as one of paleontology's great mysteries. Scientists have long speculated about the fossils known as theEdiacara biotaprimarily, about what kind of life they were.

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The ancient sea creatures have been labelled everything from giant single-celled organisms, fungi, relatives of the jellyfish and even an extinct evolutionaryexperiment 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 reinvigorate 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."

The enigma is an animal?

In a paper published by The Geological Society of the U.K., McIlroy and Dr. Suzanne Dufour, a biologist at the university, tooka 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'tmoving around much," Dufour said in a phone interview.

"One of theproblems with that mode of life is that sulfide builds up underneaththem If that's something that's toxic to you, then you're kindof in trouble."

Dufour says modern clams solve this problem by "teaming up"with bacteria. Ediacaran organisms may have had similarsymbioticrelationships, she says.

The bacteria would have used oxygen and thetoxic hydrogen sulfide as a source of energy, which would detoxifythe waters around the organism and allow it to survive.

"Animals have evolved in a world where bacteria were reallydominant. They'd already been on this planet for millions of yearsbefore animals started to evolve," says Dufour.

"It makes sensethat they would find ways to interact with them and get somebenefits from them And that's how I think animals really gottheir start."

Fostering debate

McIlroy anticipates treating the fossils as animals could fostersome debate in scientific circles about what it means to be ananimal.

An animaldoesn't need to move, but some people may be unwilling to let go ofthat concept.- Duncan McIlroy

According to some definitions, an organism has to move forit to be an animal, but McIlroy contends that this is ananachronistic view.

"If you a biologist in the Ediacaran (era), what would you callan animal?" he says.

"We tend to look at it from a modernperspective and we say, 'they all move' We would say an animaldoesn't need to move, but some people may be unwilling to let go ofthat concept."

Mistaken Point has been declared a World Heritage site by theUnited Nations Organization for Education, Science andCulture (UNESCO).