Once thought to be the fossils of shelled creatures, these features are actually the marks of gas bubbles trapped in bacterial mats. Credit: S. Bengtson et al

A decade-old dispute over the authenticity of Indian fossils that are some of the earliest examples of multicellular life seems to have been resolved. As a result, an Indian researcher has been cleared of simmering suspicions of specimen tampering.

The controversy began when palaeontologist Rafat Azmi of the Wadia Institute of Himalayan Geology in Dehra Dun reported in 1998 that he had found shell-like fossils in rocks from the Vindhyan mountain chain in central India that dated to 1.6 to 1.7 billion years ago1.

Uproar followed, because the finding suggested that animal forms had evolved much earlier than previously believed. Shelled creatures are thought to have first evolved at the beginning of the Cambrian 'explosion of life' around 550 million years ago.

In 2000, the Geological Society of India, based in Bangalore, sent a team to the site, but could not verify Azmi's initial report. When the society's journal subsequently wrote that Azmi's study was "far from convincing", media reports accused him of faking the fossils — damaging his career, Azmi says.

But research published this week in the Proceedings of the National Academy of Sciences2 reinterprets the fossils in question as traces of algae and bacteria. The purported shell-like fossils are, the authors claim, the marks of gas bubbles trapped in bacterial mats.

The samples also contain fossilized remains of filamentous algae, confirmed to be about 1.6 billion years old and possibly the earliest example of a multicellular eukaryote yet found. Similar algae had already been found in rocks dating from 400 to 600 million years later than the Vindhayan samples, but despite claims of older examples their existence before that time had remained an open question.

The samples "represent an exquisitely preserved biota of cyanobacteria and multicellular eukaryotes, previously unknown from such old rocks", says Stefan Bengtson, a palaeozoologist at the Swedish Museum of Natural History in Stockholm, who led the study. "It's a remarkable window onto ancient life, opened thanks to Dr Azmi."

"I see no evidence of fraud," he adds. "Science often progresses by the need to test 'crazy' ideas. If Azmi had not insisted on his 'Cambrian' fossils, we would not have known about this remarkable biota. He definitely didn't deserve being branded as a fraud in the Indian media."

Martin Brasier, a palaeobiologist at the University of Oxford, UK, wasn't involved in the research but has followed the debate since Azmi's original paper was published. He says the new study clears the way through the accusations to concentrate on interpretations of the fossils and their preservation. "This is what the original debate was all about," says Brasier. "The evidence is starting to show there were no animals in 'deep time'. The Cambrian explosion of animals after 550 million years ago was a real evolutionary event — like an avalanche in evolution."

Azmi says that the Geological Society of India now "has a moral duty to retract what they wrote about my work", noting that their accusations had "delayed the whole process of confirmation for nearly a decade".

The society's vice president, geologist S. V. Srikantia, says that a retraction cannot be based on the results of research published in other journals. "It is for Azmi to prove he was right," he told Nature.