February 4, 2009

Scientists Discover Earliest Signs Of Life To Date

Scientists announced on Wednesday the discovery of the earliest evidence of animal life to date.

Chemical traces found in 635-million-year-old rocks in Oman provide key evidence to support Darwin's theory that simple organisms existed before the evolution of more complex creatures, researchers said in the Feb. 5 issue of the journal Nature.

"Basically we have found a thread of that evidence that he predicted should be there," Roger Summons, a geobiologist at the Massachusetts Institute of Technology who worked on the study, told Reuters

"There is a great wealth of evidence these sponges were the first multi-cellular organisms to exist."

Reports of the new find come just a week before the celebration of the 200th birthday of English naturalist Charles Darwin.

In their study of 64 Neoproterozoic-Cambrian sedimentary rocks in south Oman, researchers came across a high amount of steroids that date back some 635 million years ago. The steroids are produced by sponges, which are considered to be one of the simplest forms of multicellular animals, researchers said.

The sponges are a few millimeters in size, immobile, and were filter feeders existing on the seafloor.

"Our findings suggest that the evolution of multicellular animals began earlier than has been thought," said Gordon Love an assistant professor of Earth sciences, who led the study.

"Moreover, sponges live on the seafloor, growing initially in shallow waters and spreading, over time, into deeper waters, implying the existence of oceanic environments which contained dissolved oxygen near the shallow seafloor around 635 million years ago."

The fossils date back very close to a massive ice age that occurred at the end of the Neoproterozoic Era. They are part of the Demospongiae class, which accounts for more than 90 percent of all sponges in existence today, researchers wrote.

Love discovered the Omani sponges while working on a project alongside Summons in collaboration with Petroleum Development Oman.

The fossils were discovered in the South Oman Salt Basin (SOSB), which is known to be one of the best sources of preserved rocks in the world.

Researchers intend to continue studying other Neoproterozoic sedimentary rocks for animal steroids just before and through the Sturtian and Marinoan glaciations, the greatest ice ages known to have occurred on Earth during 850 to 635 million years ago.

"We aim to investigate the environmental context by which multicellular animal life became viable and flourished," said Love.


Image Caption: Sponges are one of the simplest forms of multi-cellular animals. Credit: Love lab, UC Riverside.


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