Earth Life May Have Started in Ponds

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Last updated at: (Beijing Time) Saturday, May 11, 2002

Earth Life May Have Started in Ponds

The cradle of primitive life may be small freshwater ponds rather than oceans, the new edition of the British magazine New Scientist, to be published on Saturday, quoted U.S. researchers as saying.

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The cradle of primitive life may be small freshwater ponds rather than oceans, the new edition of the British magazine New Scientist, to be published on Saturday, quoted U.S. researchers as saying.

New research showed primitive cellular membranes assembled more easily in freshwater than in salty water. So, although the oldest known fossil organisms were ocean dwellers, life may actually have developed in freshwater ponds.

Most theories on the origin of cellular life presume that the first step was the formation of a spherical membrane called a vesicle that could enclose self-replicating chemical chains - the ancestors of modern DNA. The idea is that the ingredients for simple membranes were all present on the early Earth, and at some point formed vesicles spontaneously in water.

It seemed most likely that this took place in the sea rather than freshwater, largely because of the sheer size of the oceans. But research by graduate student Charles Apel of the University of California, the United States, suggests that this is wrong.

Apel and his colleagues were able to create stable vesicles using freshwater solutions of ingredients found on the early Earth, but not salty solutions. "When sodium chloride or ions of magnesium or calcium were added the membranes fell apart," Apel said. This happened in water that was less salty than the oceans are today.

Other researchers pointed out that Earth's early oceans were 1.5 to 2 times as salty as they are today, making it even more unlikely that viable cells could have arisen there.

The finding would not have surprised Charles Darwin, the founder of evolution theory. Over a century ago he speculated in his personal letters that the origin of life was "in some warm little pond with all sorts of ammonia and phosphoric salts, light,heat, electricity, etc. present."

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