Biopsychology is the branch of psychology that analyzes how the brain and neurotransmitters influence our behaviors, thoughts, and feelings. This field can be thought of as a combination of basic psychology and neuroscience (Wagner, 2005). It is also known as Psychobiology. The Merriam-Webster online dictionary defines Psychobiology as “the study of mental functioning and behavior in relation to other biological processes” (2009). This combination of the study of psychological processes and their interaction with other biological processes has led to the development of many associated fields of medical studies. This essay traces the evolution of biopsychology, its basic precepts, and connected fields. Man since ancient times knew that the mind plays an important role in physical well-being and that the two are connected. Human remains of over 10,000 years ago show evidence of Trepanation, or drilling of holes in the skull to release pain. Rene Descartes (1596-1650) made mechanical statues to test the theory of human reflex. Luigi Galvani (1737-1798) applied electrical stimulation to a frog’s leg to prove the neurological basis. Francis Gall (1758-1828) propounded the science of phrenology that stated that each bump on the skull was associated with a specific trait or characteristic. Johannes Muller (1801-1858) stated that the localization of bodily functions was located in the brain. However, a holistic theory came into being only at a much later stage when James Baldwin one of the earliest known psychobiologists propounded in 1895 that animals have adaptive mechanisms that help them to survive nature by trial and error. “This led to habit-forming that reinforced adaptations that would help the species to survive (Michel & Moore, 1995, p. 1)”. The all-embracing effect of Charles Darwin (1809-1882) whose ‘Origin of Species’ laid the foundations for biopsychology as an established field of human science cannot be underestimated. Darwin postulated that organisms evolve structure, physiology, and behavior as a response to the environment to survive, and only those species that adapt successfully survive. Thereon, scientists and researchers continued making steady progress in the development of biopsychology. Paul Broca (1824-1880), laid the foundation of neurophysiology by identifying the left hemisphere of the brain as the center for language. Thereon many associated fields came into prominence. Biopsychology also became to be variously called Sociobiology. The underlying assumption of biopsychology is that biological and genetic factors play an important role in the way humans perceive the environment and learn coping mechanisms to deal with that environment. This interrelation of innate biological factors, together with the environment gives rise to human behavioral patterns. Socio-biologists argue that no two people are born with the same brain, brain chemistry, and a thinking process that is equal. Thus, the response of two individuals to the same environmental condition would differ. People respond to the same situations differently and the learning mechanisms to deal with the environment evolve differently for two different people. Behavioral neuroscience is an associated field of biopsychology that looks at the neurobiological and biochemical processes