Oldest Evidence of Animal Life Left by Sponges?

Scientists may have come across the oldest evidence of animal life going back 660 to 635 million years, predating the Cambrian Period, a study published on Monday in Nature Ecology & Evolution revealed. It was left by the lowly sponge.

Researchers conventionally rely on body fossils when tracking animal life, with the Cambrian Period considered to be a critical point in the history of life on earth, according to the University of California Museum of Paleontology.

This is the period when most major groups of animals first appeared in the fossil record.

Now a team from the University of California, Riverside, has found hints of life that predates the Cambrian Period by at least 100 million years, Phys.org reported. They just needed to know where to look.

Rather than search for body fossils, the researchers turned to molecular signs of life, or biomarkers, and came across a steroid compound produced in the earliest forms of life – sponges.

These organisms would not have left body fossils behind because they did not contain skeletons and were probably very small, said study author Alex Zumberge.

Which is why the team of scientists searched 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.”

They discovered a steroid compound in the ancient rocks and oils from Oman, Siberia, and India, containing a structure unique to certain species of modern sponges.

This provides evidence that these sponges, and multicellular animals, were “thriving in ancient seas at least as far back as 635 million years ago,” Zumberge said.

Last month, scientists made headlines when they also used alternative methods to identify traces of life that existed millions of years ago.

In a separate study, researchers confirmed the existence of one of the earliest animal fossils by fat molecules in a strange fossil that has intrigued experts for decades.

• Argentine Dinosaur Fossil: Meat-Eater T-rosalesi Lighter on Feet Than T-rex
• Spider Fossils With Tails: 'Fantastic' Arachnid Surprise