Researchers Find Oldest Evidence of Animal Life on Earth


Researchers Find Oldest Evidence of Animal Life on Earth

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An underwater photo of the modern demosponge species Rhabdastrella globostellata, which make the same 26-mes steroids that the researchers found in ancient rocks. (Photo Credit: Paco Cárdenas)

The oldest clue of animal life, dating back at least 100 million years before the Cambrian period, when most major types of animals appear, has been found by University of California, Riverside (UCR) researchers.

The researchers have been tracking molecular signs of animal life, called biomarkers, as far back as 660-635 million years ago during the Neoproterozoic Era. They found a steroid compound produced only by sponges, which are among the earliest forms of animal life, in ancient rocks and oils from Oman, Siberia, and India.

The biomarker identified, a steroid compound named 26-methylstigmastane (26-mes), has a unique structure that is currently only known to be synthesized by certain species of modern sponges called demosponges.

The study, led by Gordon Love, a professor in UCR’s Department of Earth Sciences, was published today in Nature Ecology & Evolution.

“This steroid biomarker is the first evidence that demosponges, and hence multicellular animals, were thriving in ancient seas at least as far back as 635 million years ago,” said Alex Zumberge, author of the study, and a doctoral student working in Love’s research group.

Alex Zumberge of University of California, Riverside (right) collects 750 million-year-old rocks from a lake outcrop in Sweden. (Photo Credit: UC Riverside)

This discovery, is a result of tracking molecular fossil evidence rather than conventional body fossils.

“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. “We have been looking for distinctive and stable biomarkers that indicate the existence of sponges and other early animals, rather than single-celled organisms that dominated the earth for billions of years before the dawn of complex, multicellular life.”

Read the study “Demosponge steroid biomarker 26-methylstigmastane provides evidence for Neoproterozoic animals” at Nature Ecology & Evolution.

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