Reptilian Brain Innermost in our brain is what is called the reptilian brain, its oldest and most primitive part. The reptilian brain appears to be largely unchanged by evolution and we share it with all other animals which have a backbone. This reptilian brain controls body functions required for sustaining life such as breathing and body temperature. Reptiles are cold-blooded animals which are warmed by the daylight sun and conserve energy by restricting activities when it is dark. At this level of evolution, behaviour relating to survival of the species, such as sexual behaviour, is instinctive and responses are automatic.
Territory is acquired by force and defended.
Might is right. Next to evolve from the reptilian brain was the mammalian brain. For experience-based recognition of danger and for responding to this according to past experience. To this extent the mammal is more consciously aware of itself in relation to the environment. Millions of neural pathways connect the hippocampal and amygdala structures to the reptilian brain and behaviour is less rigidly controlled by instincts.