No. 118: Jul-Aug 1998
The lifeforms called Archaea and Eubacteria follow radically different life styles. The former are very happy in such extreme environments as the salty Dead Sea and the sea-bottom, hydrothermal vents; the latter prosper in bad hamburgers and your gut. Despite their differences, they have always been thought to have evolved from a common ancestor.
A more subtle, fundamental difference has now been found. Recall SF#117 and how some terrestrial life forms do incorporate right-handed molecules in their structures, especially in cell membranes? The ubiquitous Eubacteria do this. In the Archaea, however, the same structural components of the cell membranes (glycerophosphates) are left-handed. A subtle difference, but one with deep implications.
Some scientists maintain that it is impossible for two organisms relying upon mirror-image versions of the same molecule to have evolved from a common ancestor. Their genomes must be fundamentally different. Conclusion: the Archaea and Eubacteria must have evolved separately, and from different biological wellsprings -- that is, "creations."
Such thinking is anathema. M. Kates, a Canadian evolutionary biologist, is skeptical.
"Both the physics and chemistry of membranes are so complex that I would regard it as highly improbable that they could have auto-assembled twice."
(Barnett, Adrian; "The Second Coming," New Scientist, p. 19, February 14, 1998.)
Comment. Both opinions rely upon wild probability guesses, as do all opinions regarding the creation and evolution of life.
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