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Thursday, September 2, 2010

Oldest animals on Earth are even older

Adam Maloof and his team from Princeton have pushed back the date of the earliest multi-cellular animals by about 90 million years. Previous estimates have placed the arrival of multi-cellular organisms on Earth at about 560 million years ago. By using digital reconstruction similar to CAT scan technology to analyze nearly 500 slices of fossil-containing rock, each half the width of a human hair, the team was able to piece together organisms resembling modern sponges.

Princeton geoscientist Adam Maloof holds a rock from South Australia that may contain the oldest fossils of animal bodies ever discovered. The fossils, visible here as red shapes, suggest that sponge-like animals were in existence about 650 million years ago.

Credit: Courtesy of Adam Maloof

This is interesting for two reasons. One, prior to this study, the oldest sponges were thought to have existed for only 520 million years. These new creatures apparently lived about 650 million years ago, a considerable difference. Even more intriguing, this places the advent of multicellular life before the Marinoan glaciation event of the Cryogenian period. This event resulted in what’s termed the ‘snowball Earth’ effect in which most of the world was covered in ice. It had been thought that only single celled organisms could have survived this time period, and that multicellular animals evolved after the Earth began to warm up.