Earth's first critter was a sea sponge

The first animal to inhabit our planet was probably the sea sponge, according to a new study. Researchers with MIT performed a genetic analysis on 640-million-year-old rocks and found a molecule hailing from the lowly sea sponge. Based on this, scientists believe the creature was probably Earth's first animal, with it arriving a considerable amount of time before most other animals.

The notion that sea sponges were the first animal on Earth is not new — rather this latest study has further underscored that belief, doing so by examining so-called molecular fossils — that is, molecules from long ago that remain present in ancient objects (such as rocks), hinting at the very distant presence of the animal from which they originated.

For this study, researchers looked at the molecule 24-isopropylcholestane, 24-ipc for short. This molecule has been discovered in rocks from 640 million or so years ago, which is considerably earlier than the 540 million year old Cambrian Explosion producing most of the subsequent animals that did and do inhabit our planet.

It's just a sliver of data on some of the earliest moments in life on Earth, but sheds some light on which animal first managed to take hold on Earth. Things were tricky at first — algae can also produce the molecule type — but tests found, via a gene and some related genetic behavior, that the molecules come from sea sponges.

VIA: Discovery News