US SCIENTISTS DISCOVER SEA SPONGE DATED AT 650 MILLION YEARS OLD
Baku August 18 (AZERTAC). Scientists have discovered the ancient fossils of sea sponges which could push back the existence of animal life on Earth by 90 million years.
The tiny fossils measuring up to one centimeter across lived in ocean reefs off south Australia and were discovered in rocks dated at between 640 and 650 million years old. The remains, found by a team led by geologist Dr Adam Maloof, of Princeton University, are the oldest fossils left behind by the bodies of primitive early animals. If correct, the finding would mean that animal life existed before the Marinoan glaciation - a global catastrophe known as `Snowball Earth` when the entire planet was covered in ice. Previously it was believed that animal life first emerged after the Snowball Earth event around 635 million years ago.
Dr Maloof told The Times: `No one was expecting that we would find animals that lived before the ice age. Since animals probably did not evolve twice, we are suddenly confronted with the question of how some relative of these reef-dwelling animals survived the Snowball Earth`. Sponges are filter-feeders which extract their food from water as it flows through specialised body channels. Previously, the oldest sponges were dated at around 520million years old. The oldest known fossils of hard-bodied animals were two sea-dwelling organisms which lived around 550million years ago, called Namacalathus and Cloudina. But DNA evidence from sponges has suggested that their origins predate this. Fossils of ancient animals are difficult to study because it is hard to distinguish the remains of a living organism from the rock that encases them. X-rays can only tell the difference between materials of different densities. Martin Brasier, of the University of Oxford, said the find supported his theory that animal life kick-started `Snowball Earth`. The study has been published in the Nature Geoscience journal.
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