By Randy Boswell, Canwest News Service in Canada:
Sponge-like body believed to be oldest evidence of animals
May 5, 2009
Canadian scientists probing a mountaintop in the Northwest Territories have discovered what they believe is the oldest evidence of animals on Earth — about 850-million-year-old traces of a primitive, sponge-like organism that could push back direct proof of the origin of humanity’s own kingdom of life by an astonishing 200 million years.
The microscopic but distinctively patterned remains — unearthed from a dramatic pinnacle in the Mackenzie Mountains about 800 kilometres northwest of Yellowknife — are interpreted by the research team as rock-encased residues from the decomposed tissues of a primordial sea creature that was the earliest common ancestor of all animals, including humans.
The organism, believed to have lived in the nooks of a reef from a long-lost ocean, represents a stage of life “before sponges and other animals we know today evolved,” University of Laval geologist Fritz Neuweiler, told Canwest News Service.
Experts in evolution, including the famed Origin of Species author Charles Darwin, have long postulated that animals must have been developing eons before the existence of known creatures that left easy-to-see skeletal fossils during the Cambrian and Ediacaran geological eras, reaching back about 635 million years ago.
“If you want to go back to the very origins of animals, you can’t be looking for that,” says Laurentian University paleontologist Elizabeth Turner, one of the three co-authors of a paper detailing the Canadian discovery in the latest issue of the journal Geology.
“Earlier life won’t be that complex,” she said in an interview on Tuesday. “What we’re dealing with is a texture you can see under a microscope in a rock that’s been cut until it’s 30 microns thick. This is a wholly different type of evidence of life.”
The site is part of the Little Dal formation near the N.W.T.-Yukon border, renowned among geologists for what Turner calls its “exquisitely well preserved” record of Earth’s evolution.
“These rocks are exactly the right age for us to be exploring for this type of evidence,” she said. “We know that the earliest form of animals would have been from about 850 million years ago.”
Turner added, though, that because the fossil record is “so subtle and enigmatic at this stage” of evolution, she and Neuweiler — along with U.S. geologist David Burdige — used a “novel” series of experiments to verify their theory.
These techniques included comparisons of residue patterns found at the N.W.T. site to trace remains of younger (though still prehistoric) sponge colonies in Spain and Quebec, as well as modern sponge samples from the Bahamas.
The challenge, the researchers note in their published study, was to confirm the presence of a living organism from the dawn of animal life without the aid of “conspicuous body fossils.”
See also here.
Packed inside the humble sea sponge is a surprisingly intricate genome: it contains the basic tool kit for all animal life, including complex vertebrates – and it’s not even an animal, really: here.
Eight new kinds of the earliest animals from the Cambrian Explosion have been found in a newly explored section of ancient rock in Canada: here.