Scientists find Earth’s first animals to be 541-million-year-old; some of their traits are found in similar species alive today!

Millions of years ago, the Earth was a barren, steamy ball over half a billion years ago, full of volcanic ash, vast oceans churning with chemical soups that sparked conditions for life.

But how did these chemicals give birth to the first gooey creatures from cells? These origins fascinate because they hold clues to our own roots, and debates often center around when and where these animals actually came to life.

MIT scientists spot Earth's first animals

MIT researchers found signs of the planet's earliest animals in rocks over 541 million years old, crediting soft-bodied sea sponges as pioneers of complex life. Published in Proceedings of the National Academy of Sciences (PNAS), the study analysed Precambrian samples for "chemical fossils", steranes from ancient sterols in eukaryotic cell membranes.

Roger Summons, a lead researcher, said, “We don’t know exactly what these organisms would have looked like back then, but they absolutely would have lived in the ocean, they would have been soft-bodied, and we presume they didn’t have a silica skeleton.” These predate the Cambrian explosion, suggesting sponges lived in murky seas.

A standout discovery was steranes - they are found even today

These are molecular remnants, with uncommon 30-carbon structures typically linked to demosponges, a type of sea sponge common today. "It’s very unusual to find a sterol with 30 carbons," noted Lubna Shawar, a team member.

The researchers tested this by simulating geological burial on sterols from living sponges in the lab. The results matched the ancient rock traces exactly.

“You’re not a eukaryote if you don’t have sterols or comparable membrane lipids,” Roger Summons observed, relating these compounds to advanced, nucleus-containing cells.

Three lines of evidence include rock samples, modern sponges, and lab simulations, which have confirmed the link. "These special steranes were there all along. It took asking the right questions to seek them out and to really understand their meaning and from where they come," Shawar explained in the study.

“It’s a combination of what’s in the rock, what’s in the sponge, and what you can make in a chemistry laboratory. You’ve got three supportive, mutually agreeing lines of evidence, pointing to these sponges being among the earliest animals on Earth,” Summons concluded, as reported by MIT News.

Demosponges produce this via specific enzymes, absent in bacteria or other early life. Findings push animal origins deeper into the Precambrian, possibly rewriting evolution timelines.