The latest research from MIT reveals sea sponges may have been the first animals to inhabit the Earth. This new discovery places the sea sponge in existence even before the Cambrian explosion, known as the era when the first animals made their appearance on Earth, thus making sea sponges the oldest creatures on the planet.

Sea sponges, due to their tiny needle-like splinters called, spicules, look more like plants, but they are actually multi-cellular animals. The bottom-dwelling animals have a very simple structure. One end is permanently attached to a solid surface while the other end is open to the environment and used to collect microorganisms like, algae, as a food source.

While their appearance and structure may be simple, sea sponges are actually quite fascinating. They are able to filter their own food and pass through about 20,000 times their own volume of water in a single 24-hour period due to the tiny holes that are part of their exoskeleton. They are an asexual organism and have the ability to regenerate into new, individual sponges from even the tiniest fragments of the original organism, and can live from just a few months to 20 years or longer.

The MIT team focused on 24-isopropylcholestane (24-ipc for short), a lipid molecule that is a modified version of cholesterol. This molecule exists in rocks that are 640 million years old and has been found in sea sponges, confirming their existence at least 100 million years before the Cambrian era.

David Gold, the lead author of the scientific paper — published in the Proceedings of National Academy of Sciences —  said, “We brought together paleontological and genetic evidence to make a pretty strong case that this really is a molecular fossil of sponges.”

This finding has led to more questions than answers. Researchers now are interested in learning what these organisms looked like and what their environment was like all those years ago. Others want to know about the 100-million-year gap and why, to date, there have not been any discoveries of life during that period.