I would like to discuss the (probably) best supportive case for how this happens. (Has experimental evidence as well.) It is a recently proposed idea called Quantum Darwinism. (See peer reviewed papers in Nature and PRL.) This is how it works:
- A system begins "quantumly" in a superposition of states. (Like Schrödinger's Cat)
- After the system begins to interact with its environment, only certain states in the superposition remain stable. (Don't become destroyed.) This is called decoherence.
- A measurement by an intelligent observer also is an interaction (Example, if you look at it you hit it with a photon).
- Of the initial stable states that survive, further interactions continue to destroy "unfit" states.
- As this process continues, the surviving states actually become parent states to even more states who sometimes resemble the parent.
- This is a form of replication.
- Thus you have a bona fide survival of the fittest situation with certain states (and their offspring) becoming favored over others.
- These different stable states become "orthogonal" to each other so there is no more superposition-like quantum interactions that happen anymore.
- What emerges is a classical system. Ie.. one where it appears the wave function has collapsed.
This is a lot like ideas expressed in Dawkins' The Selfish Gene. (For those who have read it.) In that book he describes how some molecule configurations are stable and some furthermore have the added ability that they can replicate. (Make copies of itself.) Over many many years, those with the best ability to "survive" (in both the stable and able-to-replicate sense) evolve into the complex structures we see today.
This is identically the same story with Quantum Darwinism. After interactions with the environment are taken into account, only certain states are stable. Furthermore, some of these states can influence what states are created and destroyed as we run the clock forward. (They are parent states.) Those states that are best equipped for "survival" contribute to the collapsed classical structure we see today.
The PRL mentioned above cites experimental evidence for the idea. They created systems where there would be preferred stable states (after taking decoherence into account) and showed that as time when on the stable states began to replicate and a classical state emerged. See the picture.
So, Darwinian ideas may be solution to the measurement problem in quantum mechanics and therefore explain Schrödinger's Cat. Stable quantum states after interactions and "survival of the fittest" is factored in determine if the cat dies or stays alive.