The finding is significant, because similar fossil grooves and furrows found from the Precambrian era, as early as 1.8 billion years ago, have always been attributed to early evolving multi-cellular animals. 'If our giant protists were alive 600 million years ago and the track was fossilised, a palaeontologist unearthing it today would without a shade of doubt attribute it to a kind of large, multi-cellular, bilaterally symmetrical animal,' said Matz, an assistant professor of integrative biology. 'We now have to rethink the fossil record.'
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'We used to think that it takes bilateral symmetry to move in one direction across the seafloor and thereby leave a track,' said Matz. 'You have to have a belly and a backside and a front and back end. Now, we show that protists can leave traces of comparable complexity and with a very similar profile.'
With their find, Matz, Frank and their colleagues argue that fossil traces cannot be used alone as evidence that multi-cellular animals were evolving during the Precambrian, slowly setting the stage for the Cambrian explosion. 'I personally think now that the whole Precambrian may have been exclusively the reign of protists,' said Matz. 'Our observations open up this possible way of interpreting the Precambrian fossil record.'
Matz says the appearance of all the animal body plans during the Cambrian explosion might not just be an artefact of the fossil record....