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Montreal Gazette Microfossils 800 million years old; Study pushes back their age 200 million years to time before 'explosion' into larger species Add a remote Yukon mountain to the exclusive list of places around the world where scientists have discovered the earliest traces of animal life. Microscopic fossils found at Mount Slipper, a 1,500-metre peak north of Dawson City near the Yukon-Alaska border, have been dated to nearly 800 million years ago by a team of geologists from the United States. The geologists described the site as an important new record of "eukaryotic evolution" - the branch of life that eventually gave rise to humans and all other animals. The research, published in the latest edition of the journal Geology, involved a re-examination of previous studies of the Mount Slipper fossils and a fresh analysis that pushes back the age of the specimens by about 200 million years. That situates the fossil bed at a crucial time in Earth's history, when primitive, unicellular forms of life were beginning to evolve more complex structures ahead of the rise of mobile, Ediacaran-era organisms 600 million years ago and the Cambrian-age "explosion" of larger and more diverse animal species about 500 million years ago. "These microfossils are perhaps the earliest eukaryotic 'biomineralizers' - the first organisms to incorporate minerals in their body to form a shell of sorts," Harvard University geologist Francis Macdonald, lead author of the study, said in an interview yesterday. Macdonald said Mount Slipper and nearby sites in the Yukon and Alaska "preserve some of the best records in the world of Earth history between one billion and 540 million years ago, which captures the time of eukaryotic diversification and the origin of animals." The fossil records in the area "are complete, organic rich and contain volcanic ashes, which allow us to calibrate the age of our discoveries," he added. Canada's unrivalled geological diversity - including some of the world's oldest rocks and vast tracts of exposed fossils - attracts many international researchers working to record the story of evolution as it unfolded at microscopic scale in the dawning era of life. In the same edition of Geology in which the Macdonald-led study appears, a team of British and Canadian paleontologists reported the discovery in Newfoundland of the oldest evidence of animal locomotion - a 565-million-year-old fossilized trackway of an unidentified, sea anemone-like marine creature. Macdonald said the tiny Mount Slipper organism appears to have had an outer "plate" and connecting "stem" - "similar in geometry to a mushroom." He added: "It is unclear what the function of the plates was. It could have been for protection from the environment or for flotation." Last year, a team of scientists from Canada and the United States reported a major discovery in the Mackenzie Mountains near the Yukon-Northwest Territories border. They found chemical traces left by what they believe to be an 850-million-year-old, spongelike organism - possibly the oldest evidence of an animal ancestor ever found on Earth.
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