Recent advances in biological sciences provide great insights into the workings of the human brain and thereby into human nature. Drawing upon this research, my colleague Paul Lawrence and I propose a neo-Darwinian theory of human motivation based on four basic human drives that stem from our common evolutionary heritage as a species. These drives are: D1: the drive to Acquire; D2: the drive to Bond; D3: the drive to Comprehend or make sense of the world; and D4: the drive to Defend. We are now trying to test this theory through experimental and survey research. We are also searching for ways to test the theory more directly using the latest brain imaging technology..