A team of geoscientists working on a separate geological project in South Australia accidentally stumbled upon the oldest evidence of animal life yet found. Previously, the oldest fossil evidence of non-unicellular, “hard bodied” life forms dates to about 550 million years ago. This new discovery pushes back the clock on animal life by 80 to 90 million years.
That may not seem like much of a difference compared to the age of the Earth, but it’s the equivalent time difference from the modern era back to the Cretaceous period–when dinosaurs stilled roamed the Earth and swam its seas. Life forms can change dramatically over tens of millions of years.
After analysis of their tiny, fossilized parts, the team of Maloof, Rose and colleagues, determined that they most resembled an ancient form of sponge. Sponges (phylum: Ponifera) are primitive, multi-cellular, marine animals that feed by filtering nutrients and nanoplankton out of water. Their fossils are commonly found near ancient oceanic reefs.
Reported August 17 in the journal Nature Geoscience, this important, new find indicates that there were more advanced creatures inhabiting the oceans prior to this ancient Ice Age, and also that these animals were able to adapt to and survive past “Snowball Earth”.
The Princeton University research team was actually doing work on the severe, and most ancient, ice age known as the Cryogenian. It is generally believed that few, if any, animals existed previous to this severe glaciation period (known as the Marinoan Glaciation) which occurred near the end of the Cryogenian some 635 million years ago, and is believed to be the cause of the “Snowball Earth” event.
Prior to this discovery, the oldest known fossil sponges dated to the Cambrian period about 520 million years ago. Sponges are technically metazoans (multi-celled animals, possessing eukaryotic cells, i.e., those with a nucleus), but lack distinct tissue structures and a separate digestive compartment that most animals possess. It is not known if these ancient sponges’ cells possessed nuclei.
To analyze and identify the fossils in these ancient, limestone rocks, the team had to “thin slice” the rocks into hundreds of 50 micron (half a human hair width) sections.
Then, in a first for geoscience and paleontology, the team joined forces with a Brooklyn based design studio called Situ Studio, an architectural outfit that has developed software that creates a 3D digital model from many thin slices, similar to how a CT scan works. The difference here is that their technology works without x-rays (as used in CT scans).
X-rays are not useful for analyzing such ancient rocks since the fossils that they contain are made of the same material as much of the rock (calcite), and can not be visualized by x-rays, since that depends on reflecting different densities (e.g., bones and skin in living persons).
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