Swedish scientists have uncovered 1.6 billion-year-old fossils that indicate multi-cellular life developed much earlier than previously thought - possibly 400 million years earlier.
Therese Sallstedt of the Department of Palaeobiology at the Swedish Museum of Natural History was examining fossilized, layered mats of cyanobacteria collected in an ancient rock outcrop in central India when she came across what appear to be primitive algae fossils.
Cyanobacteria are basic, single-cell life forms that have existed for nearly 3.5 billion years and are among the oldest fossils known.
"I was studying the mat biota, expecting to find more variations of bacteria," Sallstedt said in an email. She didn't expect to find well-preserved fossilized algae, which was much bigger and more complex than the surrounding bacteria. She became "very excited."
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The newly-discovered algae, by comparison, lived approximately 1.2 billion years before the first plants are thought to have appeared on land.
The rock samples come from an area dotted with dozens of Hindu temples between the towns of Jankikund and Chitrakoot along the Son River Valley in Uttar Pradesh and Madhya Pradesh. The surrounding rocks consisted mostly of calcium and magnesium carbonates. But the cyanobacteria and algae fossils were preserved in a layer of calcium phosphate, which preserves finely detailed cellular structures that can be explored with X-ray tomography.
"Phosphate is something of an almost magical substance when it comes to preserving fine-scale details, like intercellular features in fossils," Sallstedt said. "Sedimentary phosphate deposits such as this can therefore open up a window of sorts into other time periods since the preservation is so good."