Econintersect: Noted chemist Ronald Breslow has asked a question: Why are the spatial orientations of complex molecules of most proteins and sugars 
predominantly occurring in nature found mostly in only one of the two possible structures?
The Columbia University chemist, and former president of the American Chemical Society, has some suggestions about how natural processes in the universe could have produced the chemical outcome that is observed. But an intriguing thought comes from a rhetorical question he asks: What would life be like if it were based on the molecules of the opposite orientations from those of the proteins and sugars that predominate here on earth?
This esoteric discussion derives from an article just published (March 25) in The Journal of the American Chemical Society. In that article Breslow reviews some chemical processes that could have resulted in the spatial orientation discrimination as we observe it on our planet. From that comes an obvious thought that maybe other chemical processes elsewhere in the universe could produce predominantly the alternate spatial orientations for the building block molecules of life. If that happened, would the outcomes of higher life forms have been dramatically different?
Perhaps in an alternate scenario the outcome would have a planet ruled by dinosaur-like races of creatures with intelligence rivaling or exceeding that of humans. Imagining such possibilities makes “Planet of the Apes” seem pretty tame.
Editorial note: There is no reason why such dramatically different dominant life forms could not have occurred on Earth with the molecules that we have here. The evolution of life forms hinges on many discrete and rather arbitrary sequences of events. For example, the extinction of most of the large dinosaurs which gave room for the development of primates as advanced life forms is believed to have hinged on a single astro-geological event some 65 million years ago. Had that not occurred as it did earth might be ruled by dinosaur descendants today.
This above is an intellectual exercise that can be pursued until you bring religious beliefs into the discussion.
Sources:
- Intelligent space dinosaurs: How worried should we be? (Eoin O’Carroll, Christian Science Monitor, 12 April 2012)
- Evidence of the Likely Origin of Homochirality in Amino Acids, Sugars and Nucleusides on Prebiotic Earth (Ronald Breslow, Journal of the American Chemical Society, 25 March 2012)
