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Science Frontiers ONLINE No. 118: Jul-Aug 1998 |
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Two Creations Of Life?
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.