For nearly 100 million years, sponges alone ruled the seas. In a study published in this week’s Nature, researchers found chemical traces of sponges that were over 635 million years old. That’s 100 million years before the Cambrian Explosion, when the first (really creepy looking!) animals were thought to have appeared.
The chemical traces of these sponges are the oldest record of animal life ever to be found in the fossil record. Their tiny spongy lives would have been lived alone (except for single-celled organisms) in the shallow, frigid seas of an ice age. But with no other animals to eat them, there were probably plenty of fellow sponges. According to Gordon Love, the lead author:
“There was no competition from more complicated animals, so sponges were probably thriving,” Love said. “Compared with other times in our history, there were enormously high amounts of them.”
These ancient sponges eventually gave rise to all other animal life, though some of their descendants scorned higher organization for the loose & easy life. Since more than 90% of modern sponges resemble those ancient sponges, perhaps there’s something to be said for a simple life of filtering seawater and spawning.
Gordon D. Love, Emmanuelle Grosjean, Charlotte Stalvies, David A. Fike, John P. Grotzinger, Alexander S. Bradley, Amy E. Kelly, Maya Bhatia, William Meredith, Colin E. Snape, Samuel A. Bowring, Daniel J. Condon, Roger E. Summons (2009). Fossil steroids record the appearance of Demospongiae during the Cryogenian period Nature, 457 (7230), 718-721 DOI: 10.1038/nature07673