Later On

A blog written for those whose interests more or less match mine.

Origin of life on earth

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It looks very much as if scientists have tracked down how life originated on earth: the locale (in general terms) and the mechanisms linked in a very plausible scenario. Our ultimate ancestor’s first evolutionary steps were bacteria and archaea, both single-celled organisms. From the New Scientist article by Nick Lane:

It looks as if DNA replication evolved independently in bacteria and archaea, according to Eugene Koonin at the National Center for Biotechnology Information in Bethesda, Maryland.

Beyond that, many biochemical pathways are catalysed by quite different enzymes. The most surprising and most significant of these is fermentation, the production of energy from food without oxygen. Fermentation is often assumed to be the primordial method of energy generation. Yet Martin has shown that the enzymes responsible are totally unrelated in archaea and bacteria. It looks as if fermentation evolved twice later on, rather than at the dawn of life.

Even more baffling, says Martin, neither the cell membranes nor the cell walls have any details in common. "At face value, the defining boundaries of cells evolved independently in bacteria and archaea," he says.

But if that’s the case, what sort of a cell was this common ancestor? A cell with no boundary? Impossible! Something unique? If you exclude the impossible, then whatever you are left with must be true.

Fascinating article. I’m delighted that a plausible scenario for the origins of life has been formulated.

Written by LeisureGuy

29 November 2009 at 9:22 am

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