Fruit flies and other animals seem to have mechanisms built into their brains that can determine just how probabilistically they should react to a given scenario - in one where all available options are roughly as good as each other, the fly is likely to pick at random, while a situation where only one choice doesn't result in death will lead to a pretty much instinctual response.
So, the fly is not just a little machine but an actual being in the world of death and decisions.

Should I stay or should I go?
  • Wikipedia
  • "Should I stay or should I go?"
The mind behind this new line of thinking (Björn Brembs) claims that free will has an evolutionary advantage: it means actions of creature are not so predictable to its prey or predators. Animals that have a free will will preform better than animals that don't. What this also means is that free will is one possibility of being and having no free will is another possibility. The universe is vast, so there must be some planets or places where free will is a disadvantage.