''So it is part of human physiology? Are you sure?''
It is the function of the physical system, the neural architecture of a brain that enables our ability to perceive, think and act.
That is proven through structural and/or chemical changes to the physical system, lesions or chemical imbalances, etc.
For instance;
The Neural Correlates of Consciousness ''The Neural Correlates of Consciousness (NCC) can be defined as the minimal neuronal mechanisms jointly sufficient for any one specific conscious percept (Crick & Koch 1990).''
''Progress in addressing the mind-body problem has come from focusing on empirically accessible questions rather than on eristic philosophical arguments. Key is the search for the neuronal correlates - and ultimately the causes - of consciousness.''
''The question of interest is which of its subcomponents are essential to produce a conscious experience (Fig.1). For instance, it is likely that neural activity in the cerebellum does not underlie any conscious perception, and thus is not part of the Neural Correlates of Consciousness. That is, trains of spikes in Purkinje cells (or their absence) will not induce a sensory percept although they may ultimately affect some behaviors (such as eye movements).''
''Every phenomenal, subjective state will have associated Neural Correlates of Consciousness: one for seeing a red patch, another one for seeing grandmother, yet a third one for hearing a siren, etc. Perturbing or inactivating the Neural Correlates of Consciousness for any one specific conscious experience will affect the percept or cause it to disappear. If the Neural Correlates of Consciousness could be induced artificially, for instance by cortical microstimulation in a prosthetic device or during neurosurgery, the subject would experience the associated percept. ''
