Indian geologic strata holds clue to oldest known animal life; all you need to know

by Elton Gomes

Researchers in the US have found the oldest clue yet of animal life in ancient rocks and oils. These ancient rocks and oils were found in India, Oman, and Siberia, and reportedly date back at least 100 million years before the famous Cambrian explosion of animal fossils.

Researchers at the University of California in the US were able to track molecular signs of animal life, known as biomarkers, the signs date back as far as 660-635 million years ago during the Neoproterozoic Era.

In ancient rocks and oils, which were found in India, Oman, and Siberia, the researchers found a steroid compound that is produced only by sponges – which are known to be among the earliest forms of animal life.

The Cambrian Explosion refers to the period when there was a sudden appearance in the fossil record of complex animals with mineralised skeletal remains 541 million years ago.

“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,” Alex Zumberge, a doctoral student at University of California, said, PTI reported.

What have the scientists found?

The researchers have identified a biomarker, which they say is a steroid compound named 26-methylstigmastane (26-mes). This biomarker has a unique structure that currently can only be synthesised by certain species of modern sponges that are known as demosponges.

“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,” Zumberge said.

What do the findings suggest?

The findings of the biomarker 26-mes supplement the fact that both compounds are fossil biomolecules produced by demosponges on an ancient seafloor, researchers said.

The study also provides new constraints on the groups of modern demosponges that are capable of producing unique steroid structures, which leave a distinctive biomarker record. The researchers found that in modern demosponges, certain taxonomic groups preferentially produce 26-mes steroids whereas others produce 24-ipc steroids.

“The combined Neoproterozoic demosponge sterane record, showing 24-ipc and 26-mes steranes co-occurring in ancient rocks, is unlikely attributed to an isolated branch or extinct stem-group of demosponges,” Gordon Love, a professor at the University of California, said, as per a PTI report.

Why is this important?

The ancient date of the steroid biomarker is important because it demonstrates that animals lived at least 100 million years prior to the Cambrian explosion, which occurred 540 million years ago.

For a long time, scientists were under the impression that organisms that lived before the Cambrian explosion were simple single-celled creatures. However, it is now becoming increasingly clear that there have been animals existing in ancient seas even before the Cambrian explosion occurred.

It is important to note that evidence of some of the oldest animals might come from chemicals, and not bones or preserved flesh. The oldest known animal fossil, which was identified to be a 558 million-year-old ribbed creature, was identified in September after its body left behind bits of organic material.

Elton Gomes is a staff writer at Qrius