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Oldest evidence for animals found



The study led by Gordon Love, a professor in UCR's Department of Earth Sciences, was published today in Nature Ecology & Evolution . The first author is Alex Zumberge, a doctoral student working in Love's research group.

Rather than searching for fossil fossil bodies, the researchers have been studying molecular signs of animal life, called biomarkers, as far back as 660-635 million years ago during the Neoproterozoic Era. In ancient rocks and oils from Oman, Siberia, and India, they are produced by sponges, which are among the earliest forms of animal life.

"Molecular fossils are important for tracking early animals since the first sponges were probably very small, did not contain a skeleton, and did not leave a well-preserved or easily recognizable body fossil record, "Zumberge said. The biomarker. "The biomarker." The biomarker. "1965. The biomarker they identified, a steroid compound named 26-methylstigmastane (26-mes), has a unique structure that is currently being synthesized by certain species of modern sponges called demosponges.

    

UCR's Alex Zumberge (right) collects 750 million-year-old rocks from a lake outcrop in Sweden. Credit: UC Riverside
    

"This steroid biomarker is the first evidence that demosponges, and multicellular animals, were thriving in ancient seas at least as far back as 635 million years ago," Zumberge said.

The work builds from a 2009 study by Love's team, which reported the first compelling biomarker evidence for Neoproterozoic animals from a different steroid biomarker, called 24-isopropylcholestane (24-ipc), from rocks in South Oman. However, the 24-ipc biomarker evidence proved controversial since 24-ipc steroids are not exclusively made by demosponges and can be found in a few modern algae. Fossil biomolecules produced by demosponges on an ancient seafloor.

The study also provides important new constraints on the groups of modern demosponges capable of producing unique steroid structures, which leave a distinctive biomarker record. 24-ipc steroids.

"The combined Neoproterozoic demosponge sterane record, showing 24-ipc and 26-m sterane co-occurring in ancient rocks, is unlikely attributed to an isolated branch or extinct stem group of demosponges, "Love said. The title of the paper is "Demosponge steroid biomarker 26-methylstigmastane provides evidence for Neoproterozoic animals. "
                                                                


Explore further:
                                        Fat from 558 million years ago reveals earliest known animal
                                    

More information:
                                        J. Alex Zumberge et al., Demosponge steroid biomarker 26-methylstigmastane provides evidence for Neoproterozoic animals, Nature Ecology & Evolution (2018). DOI: 10.1038 / s41559-018-0676-2
                                        

Journal reference:
                                                                                                            Nature Ecology & Evolution
                                                        
                                                        
                                                                                                    

Provided by:
                                                                                                            University of California – Riverside
                                                        

                                                        
                                                                                                    


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