First Animal on Earth was Likely a Sea Sponge (VIDEO)

First Posted: Feb 26, 2016 08:04 AM EST

The first animal on Earth was likely a sea sponge. New genetic analysis has shown that sea sponges are the source of a curious molecule found in rocks that are 640 million years old.

Paleontologists have unearthed a lot of fossils starting from the period around 540 million years ago. Based on this record, researchers believe that this was when life effectively "exploded" onto Earth and morphed from simple single-celled organisms to complex multicellular animals in a relatively short amount of time. However, the fossils before this time are difficult to analyze.

In this latest study, the researchers focused on a 24-isopropylcholestane, or 24-ipc. This is a lipid molecule that is a modified version of cholesterol. It can be found in strangely high amounts in Cambrian and slightly older rocks.

Researchers know that some modern sea sponges and certain types of algae produce 24-ipc today. First, the researchers identified which gene is responsible for making 24-ipc, and then traced back when the gene evolved in these organisms. In the end, the researchers found that the ancient 24-ipc was probably from sea sponges.

"We brought together paleontological and genetic evidence to make a pretty strong case that this really is a molecular fossil of sponges," said David Gold, one of the researchers, in a news release. "This is some of the oldest evidence for animal life."

The findings reveal a bit more about the ancient animals that once inhabited our oceans. More specifically, it shows how sea sponges may have been the first animals on Earth.