True, we are influenced by many factors beyond our control. However, just because we cannot isolate the causes or motivations for something does not mean we have no control over the course of events. I think of it this way: our enviroment and heredity are the vehicle and fuel of our actions. We probably don't have control of the accelerator and brakes all the time, but we often have good control of the steering. Just because we can't control our speed doesn't mean we can't control our direction. To say that we must have full control or no control would be a false dilemma.
Arguments about such things are fruitless, however, because we can't argue conclusively and concretely about the causes of our thoughts with thoughts alone. Such reason could only come from a source external from the human condition, and none of us know of or communicate with such a source, if it even exists. I can't conclude that environment and desire and need is the only thing mandating our actions, though. To live in society, we forego and repress our most base desires everyday. Ever read any Freud?
I agree with your statement about the difference between us and monkeys--it all comes back to Rene Descartes saying "cogito, ergo sum." Thoughts, while impotent in regards the knowledge of their own nature, are still mankinds' greatest resource.