A rock from South Australia that may contain the oldest fossils of animal bodies ever discovered.
A rock from South Australia that may contain the oldest fossils of animal bodies ever discovered.
Courtesy of Adam Maloof

Princeton scientists reported last month that they have found what may be the oldest fossils of animals — primitive spongelike creatures that may have lived in ocean reefs 650 million years ago. If confirmed, the fossils would push back the date of the oldest known animal forms by 70 to 90 million years.

The fossils were found in 2007 under a glacial deposit in South Australia by a team led by geosciences professor Adam Maloof and graduate student Catherine Rose. Their findings were published in the Aug. 17 issue of Nature Geosciences.

The research team had been focusing on the “snowball Earth” event that marked the end of the Cryogenian period 635 million years ago, leaving most of the planet covered in ice.  

“No one was expecting that we would find animals that lived before the ice age,” Maloof said, “and since animals probably did not evolve twice, we are suddenly confronted with the question of how some relative of these reef-dwelling animals survived.”  

Because the fossils were made of the same material as the rock in which they were embedded, they couldn’t be removed by conventional techniques or analyzed by X-rays. Working with Situ Studio, a design and digital fabrication studio in Brooklyn, N.Y., the team ­created digital reconstructions of two fossils by shaving nearly 500 micro- scopically thin samples from the rock and photographing the surface as each sample was removed.