Edging Back
Life’s older than thought
A three dimensional X-ray image of the outer (left) and inner (right) body of a fossil from the Gabonese site
Researchers have found what may be the earliest evidence of multicellular life on Earth. Large fossils uncovered in 2.1 billion-year-old rock from Gabon, in western Africa, appear to be incipient examples of macroscopic life in what was then a sea of single-celled microbes. Scientists believe that multicellular life really took off much later, in the great expansion of animal body plans known as the Cambrian explosion 545 million years ago. "The discovery is fantastic because it shows the existence of multicellular fauna 1.5 billion years earlier than what we know," says team leader Abderrazak El Albani, a sedimentologist and paleobiologist at the University of Poitiers in France. "This is important to understand the evolution of life on Earth." Some researchers have suggested multicellular organisms arose as early as 1.6 billion years ago, but the evidence is controversial. El Albani and his colleagues were thus surprised to find large fossils in the newly excavated ancient Gabonese rocks. So far, the team has collected over 250 specimens that range in size from 1 to 12 centimeters. Using detailed X-ray imaging called microtomography, the team created three-dimensional images of the fossils inside and out. The organisms had flat, round, soft bodies, with slits around the edges and complex, patterned folds inside. The creatures belong to new species that have never been described, the team reports in the July 1 Nature. Other researchers agree that the large size, thickness, and three-dimensionality of the organisms suggest that they were, indeed, multicellular. "There does seem to be something more than just a clonal colony of bacteria," says paleobiologist Philip Donoghue of the University of Bristol in the United Kingdom. El Albani and his team believe the complex patterns and folding mean that cells must have coordinated their growth through chemical signaling, like all multicellular organisms do. The fossils could even be the first examples of eukaryotes, cells with membrane-bound nuclei, according to the team.
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