A Multiverse Computation?
According to the Many Worlds Interpretation of quantum mechanics, the answer to questions about why Nature chooses one possibility rather than another in probabilistic events, such as one of several decay paths of an excited atom, is that it doesn't -- everything that can happen does happen somewhere, but in different realities that don't communicate. It's an SF writer's godsend for things like alternate histories and time travel, and I used it in The Proteus Operation. Later, as I said in the Dedication of Paths to Otherwhere, an evening in London with Oxford quantum physicist David Deutsch persuaded me that it was real, and the book was partly the result.
The weirdness of quantum effects, such as particles apparently interfering with themselves, is explained by nearby realities interfering at the quantum level, i.e. at the smallest scale the barrier to communication breaks down, enabling information to "leak" through. Paths begins with a research group at Berkeley who are investigating the uniqueness of living things as arising from their ability at the molecular level to tap into this vast exchange of information across a virtually infinite number of universes to accomplish the stupendous computation implied by evolution, which by the time the book is set in, is accepted as impossible within the bounds of a single universe such as the one we know.
On account of all of which, I was delighted to hear from a Dr. Johnjoe McFadden, a Reader in Molecular Microbiology at the University of Surrey in the UK, who has been working on exactly this kind of theory and was referred to Paths by one of his graduate students. He also sent me a copy of his own recently published work, Quantum Evolution: The New Science of Life, both fascinating and informative, intended for the non-specialist readership. McFadden makes the point that living organisms are controlled by a single molecule, DNA, and unlike the bulk processes that make up the familiar physical world, living systems operate by specifically manipulating single particles, such as the transfers of ions and electrons in the metabolism. Such behavior is governed not by the classical laws that conventional biology has attempted to apply, but by quantum mechanics. By being able to select from a superposition of states stupefyingly vaster than anything imagined within orthodox evolutionary theory, organisms acquire the ability to initiate specific actions and mutations that direct their evolution toward favored ends. (Evidence for directed mutations has been accumulating for many years but has been largely ignored or denied since it goes against the principle of randomness that current dogma demands.) You may click here if you wish to visit Dr. McFadden's Web site.
Quantum Evolution: The New Science of Life, e-mail Dr. Johnjoe McFadden, Harper Collins, 2000. ISBN 0-00-65128-9