Evolution at the Micro/macro Interface

Most recent answer: 04/04/2013

Q:
Can one consider life to be in a sense uniquely existing along the interface between the microscopic quantum and the macroscopic realms? Consider life evolving through long periods of time. The process of evolution basically involves formation of genetic mutations and the process of natural selection which determines which of those mutations become spread through a population. Many if not all mutations involve individual quantum level events while the process of selection is a macroscopic process. The molecular mutations can directly be reflected in macroscopic phenotype of an organism which might then have some effect its the survival chances, and thereby the likelihood of the mutation to be propagated. A continual flow of quantum randomness into DNA which the process of life then cherry-picks, as it were, makes the continuation of life through geological time possible.
- Jack Stephens (age 70)
Neptune Beach, Florida
A:
That's a very interesting and thoughtful perspective. I'll add some minor caveats.

Life is not uniquely at that interface. Other physical events can amplify quantum processes to produce a range of distinct macro outcomes. Any quantum measurement we do in a lab is an example. One could argue that these experiments are themselves a sort of appendage to life. Accidental quantum experiments can occur without living involvement, however. For example the sorts of photon-matter interactions that leave a weakly exposed photographic film blotchy can occur with non-living chemicals, leaving random patterns. Still, as you say, life is an outstanding factory for converting quantum randomness to a variety of macro outcomes.

It may be pointless to speculate about a counter-factual non-quantum world, but I'm not sure that quantum randomness is necessary for evolution. Imagine that the mutations caused by UV light occurred without quantum randomness but just depended on the accidents of which DNA spots happened to be hit by little classical particles coming from a distant sun. For the purposes of evolution, that might play the same role as quantum randomness.

Mike W.

(published on 04/04/2013)

Follow-Up #1: life amplifying quantum fluctuations

Q:
This is a follow-up on the question 'evolution at the micro/macro interface'. Perhaps I did was not clear in my use of the word uniquely the my first sentence. What I was driving at is that the phenomena of life existing through vast time periods depends on the flow of mutations as the raw material for the process of adaptation to changing environments. In this sense mutations are an essential part of the natural phenomena called life. Furthermore individual mutations can produce specific macroscopic effects which can persist for billions of years and interact with other mutations to produce an endless stream of higher order effects. I know of no other phenomena in which individual quantum level events can interact with the macroscopic world in such a complex way. This is what I meant by using the word 'uniquely'. I used the wording 'Many if not all mutations involve individual quantum level events' to leave open the possibility of non quantum level mutations. The UV radiation example would only work if it affected germ cells which tend to be highly protected in all but the simplest organisms.
- jack stephens (age 70)
Neptune Beach, Florida
A:
Your point about life being special is important. I should have pointed out that there are other large-scale cases, e.g. rotations of a  highly asymmetric moon (I forget of which planet) in which quantum fluctuations appear to lead to multiple macroscopically different states. The differences are genuinely large scale, giving an essentially random orientation of the entire moon after some years have passed. The rule of thumb is that classically chaotic systems are ones that are very sensitive to small-scale perturbations, so quantum spreads can lead to diverse outcomes. The case of life is certainly more interesting.

For my UV case, substitute penetrating cosmic rays, less common but able to get to germ cells.

Mike W.

(published on 04/06/2013)