Cavity-riddled masses of iron sulfide formed naturally where hydrothermal vents spewed warm, compound-rich fluids into deep-sea waters, explains geologist Russell. These "culture chambers" provided just the sort of incubator that the chemical ingredients of life needed to initiate biochemistry.
"These inorganic compartments were the precursors of cell walls and membranes found in free-living [cells]," Martin and Russell wrote.
Trapped within their inorganic incubators, "the first cell couldn't feed itself," said Russell. "Like a child in the womb, it had to be fed, to be nurtured" by the stream of nutrients and energy that continued to bubble up from the hydrothermal vents beneath them, he said.
It doesn't sound like an easy way to live, but there must have been multiple ways to pull it off, Martin and Russell argue, because there are three fundamentally different forms of life. Two of themthe eubacteria and their simple cousins, the archaebacteriadiverged evolutionarily even at this early stage in the history of life, they suspect.
From these humble beginnings, however, life would soon burst forth into a new and exciting worldthe juvenile Earth.
First, the researchers hypothesized, biological processes produced and deposited fatty molecules along the inner surfaces of the iron sulfide cavities. Eventually, these fats formed into cohesive membranes that fully enclosed the biological activity inside. Archaebacteria and eubacteria arose independently from parallel occurrences of this series of events, Martin and Russell proposed.
That landmark development rendered obsolete the original, inorganic compartments, and the first true cellular life was ready to emerge. When the first of these organisms broke free from the confines of their iron sulfide cocoons, said Martin, "they were all alone in an uninhabited planet."
"This lonely little spot" of life might have evolved quickly, Martin hypothesized, because virtually every adaptation that arose opened up whole new classes of untapped chemical resources in the organisms' submarine world. "It's as if you went into a bank [for the first time], and they gave you all the money."
The Whole Trinity
Eventually, organisms became numerous enough that competition among them ensued. That, Martin and Russell suggested, may have been when some eubacteria and archaebacteria hit on the strategy of joining forces, thereby forming the third class of life, the eukaryotes.
These organisms, composed of complex cells with complete, organ-like internal structures, include all multi-cellular life forms such as plants and animals. The ancient strategic merger that created them explains why most eukaryotes resemble eubacteria in certain biochemical respects but depend on archaebacteria-like internal organelles such as mitochondria or chloroplasts, Martin and Russell asserted.
That argument, like many the pair of researchers has made in their new model of life's origins, broadsides conventional wisdom.
Martin and Russell fully expect their theory to be held to the fire that burns in the crucible of rigorous scientific discourse.
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