Sea sponges may not look like much, but if seniority on our planet means anything, they deserve your unwavering respect. According to new research published today in the Proceedings of the National Academy of Sciences, these ancient marine creatures were likely the first animals ever to evolve on Earth—despite the comb jelly’s recent bid for that title.
The paper’s authors, led by MIT biologist David Gold, were able to back up their candidate with “molecular fossils,” which are trace fragments of organic material, that date back 640 million years to the Cryogenian geological epoch.
“There’s a feeling that animals should be much older than the Cambrian (the period running from 541 to 485 million years ago), because a lot of animals are showing up at the same time, but fossil evidence for animals before that has been contentious,” Gold said in a statement. “So people are interested in the idea that some of these biomarkers and chemicals, molecules left behind, might help resolve these debates.”
Explainer of new PNAS paper. Video: YouTube/Massachusetts Institute of Technology (MIT)
In this case, the relevant compound was 24-isopropylcholestane (24-ipc), a riff on cholesterol, which was found in Cryogenian rock samples. By stacking the genomes of 30 species against each other, Gold and his colleagues found that sea sponges are especially proficient producers of 24-ipc, which links their ancient lineage to the relatively abundant levels of the molecule found in pre-Cambrian rocks.
It seems that, once again, sea sponges have been scientifically validated as the real OGs of evolutionary history. Considering that they have branched out into at least 5,000 unique species since those early days, it’s fair to say that these bizarre, diverse creatures have earned a little old school cred.