[China, UK] Ancient fossils that date back around 600 million years, were thought to be some of the world’s earliest examples of animal remains.
But a controversial new study claims that this may not be the case.
Researchers have re-examined the fossils, and believe that the remains could in fact be algae.
The Weng’an Biota are a group of well-preserved fossils in South China that were first discovered in 1998.
The fossils provide a snapshot of marine life during the time in which molecular clocks estimate that animal groups evolved.
Dr John Cunningham, from the University of Bristol’s School of Earth Sciences and an author of the study, said: ‘Dated at around 600 million years old, these rocks preserve an assemblage of microscopic fossils, perfectly-aged to be candidates for the oldest evidence of animal life.
‘These fossils aren’t recognisable as remains of fully grown animals, but some resemble embryos, ranging from single cells to clusters of thousands.
‘The preservation is so exquisite, that even sub-cellular structures can be identified, including possible nuclei.’
But the researchers are sceptical of the fossil evidence from this time, and believe the Weng’an Biota fossils aren’t necessarily animal remains.
Dr Kelly Vargas, an author of the study, said: ‘With the lack of adult forms that could indicate their identity, palaeontologists have to rely on information from cellular anatomy to determine whether these tiny fossils belong to animals or to a different group.’
The researchers reviewed all the evidence pointing to an animal identity of the fossil, and discovered that none of the characteristics used to define the fossils as animals are unique to animals alone.
This opens up the possibility for alternative identifications.
Professor Philip Donoghue, another co-author, added: ‘Many proponents of animal affinity have argued that the Y-shaped junctions between the cells in the fossils are an important animal character, but this is a feature common to many multicellular groups, including algae, that are very distant relatives of animals.’
Dr Cunningham added: ‘It could be that the fossils belong to other groups, such as algae, and these possibilities need to be investigated carefully.’
The researchers hope their findings will help to refine our knowledge about evolution during this period.
Dr Cunningham concluded: ‘It might be possible that we’ll find definite animals, but it’ll be like finding a needle in a haystack, or should we say an embryo in a really, really big quarry.’
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