In his 1984 book, Elbow Room: The Varieties of Free Will Worth Wanting, the American philosopher, Daniel Dennett, explores what it means for people to have free will. He considers whether we are deterministic machines (e.g. genetic) with no real freedom of action or do we in fact have some elbow room, some real choice in our behavior?

Denett clearly describes what people are as biological entities and why free will is of critical importance. In discussing what people are and why free will matters to us, Dennett makes use of an evolutionary perspective. Dennett describes the mechanical behavior of the digger wasp Sphex. This insect follows a series of genetically programmed steps in preparing for egg laying. If an experimenter interrupts one of these steps the wasp will repeat that step again. For an animal like a wasp, this process of repeating the same behavior can go on indefinitely, the wasp never seeming to notice what is going on. This is the type of mindless, pre-determined behavior that humans can avoid. Given the chance to repeat some futile behavior endlessly, people can notice the futility of doing so, and by an act of free will do something else. We can take this as an operational definition of what people mean by free will.

From a biological perspective, what is the difference between the wasp and a person? The person can, through interaction with his/her environment, construct an internal mental model of the situation and figure out a successful behavioral strategy. The wasp, with a much smaller brain and different genetic program, does not learn from its environment and instead is trapped in an endless and futile behavioral loop that is strictly determined by its genetic program. It is in this sense of people as animals with complex brains that can model reality and appear to choose among several possible behaviors that Dennett says we have free will.

Another thought derived from the concept of free will is that it is required in order to have immoral behavior. The wasp that is programmed to sting a perceived threat is not immoral; a human who commits murder through choice, is considered to be potentially immoral.

Most philosophers agree that humans have a degree of choice and free will. There is little evidence to date of broad genetic pre-determinism for behavior of humans.
However, there is still some controversy on whether or not environmental influences do activate some genetic predispositions toward violence or other anti-social behaviors.