Eden one. It certainly is not proof of evolution, but it is proof of concept. The magnets are the key. In nature, biological system do undergo certain random mutations. Imagine that you throw another variable to the above experiment, where the magnets would change shapes randomly. At some point, two pieces would have a chance of having the right fit and they will unite. In this case we are putting together a chair. If a leg happens to mutate on a magnet that fits the arm rest, then the chair is useless. In nature, natural selection would take care of eliminating this useless chair. Eventually, one will form that will fit the environment and survive.
The environment plays a huge roll, probably as big as genetic mutations if not bigger. Here is an example. Studies in the south parts of the US has shown that rattle snakes are developing this rare mutation. One where the rattlers are not good and they don't make any noise. The snakes with this mutation are surviving and reproducing, while the population of healthy snakes is declining. Biologists have determined that the mutation itself is only physical, it poses no health risks for the snake (no diseases or anything that would kill it naturally). After some time. they determined that those healthy snakes are always able to warn bystanders of their presence, which ends up with the human killing the snake, while the one with the mutation is not able to warn anyone of its presence, therefore surviving the human threat. It then goes on to reproduce, carrying the mutated gene forward.
Let there be light..