A Canadian geologist has found what may be the oldest fossil record of animal life on Earth, according to a report published Wednesday in the journal Nature.
About 1 billion years ago, an area of northwestern Canada now characterized by rugged mountains was a marine environment where the remains of ancient sponges could be preserved in mineral sediments, according to the work.
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Geologist Elizabeth Turner discovered the rocks in a remote area of the Northwest Territories accessible only by helicopter where she has been digging since the 1980s. Thin slabs of rock contain three-dimensional structures similar to the skeletons of modern sponges.
“I think they are old sponges – it’s the only organism that has this kind of organic filament network,” said Joachim Reitner, a geobiologist and sponge specialist at the University of Göttingen, Germany, who does did not participate in the study.
Samples of adjacent rocks indicate that they are around 890 million years old, 350 million years older than the undisputed sponge fossils previously found.
“The most amazing thing is the date,” said Paco Cárdenas, a sponge expert at Uppsala University, Sweden, who was not involved in the research. “The discovery of fossil sponges nearly 900 million years ago will dramatically improve our understanding of early animal evolution.”
Many scientists believe that the earliest animals included soft sponges or sponge-like creatures devoid of muscles and nerves, but with other simple animal characteristics, such as cells with differentiated functions and sperm.
Granted, there is little scientific consensus or certainty about anything that existed 1 billion years ago, so other researchers will continue to investigate and debate Turner’s findings.
Scientists believe that life on Earth appeared around 3.7 billion years ago. The first animals appeared much later, the exact time is debated.
So far, the oldest undisputed fossil sponges date back to the Cambrian period, around 540 million years ago.
But a method of reasoning called the molecular clock – analyzing the rate of genetic mutations to determine the likely time two species diverged – indicates that sponges appeared much earlier, 1 billion years ago.
What was lacking so far was physical evidence.
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