Taken from a document I use to keep track what I've learned about the development of human thought over the past fifteen years.
"Something beyond our understanding occurs...the transformation of an objective cerebral computation into a subjective experience."
Basic sentience possibly arises from a mapping function in which sight, sound, touch, smell, and feel are woven together into a representation of the external world and internal body. Such an animal consciousness perceives only the timeless continuum of the now, and its first apprehension of the past was the short-term memory system, which holds impressions for just seconds or minutes in the form of electrical currents between neurons.
Procedural memory--also known as reflex memory or muscle memory--was the first system of durable memory to arise in our evolutionary history. Procedural memory involves protein synthesis, writing out new neurons or strengthening existing neural connections, thus allowing organisms to learn new physical skills as well as to refine innate reflexive skills passed down genetically--skills commonly referred to as instincts.
Declarative memory arose as a mechanism for storing and recalling two types of information: episodic and semantic. The episodic memory subsystem encodes the autobiographical recall of past situations that have been experienced. The second subsystem, semantic memory, stores information that is independent of the situation in which it was learned.
Semantic memory allows for the creation of meaning by enabling individuals to remember the abstract commonalities of multiple events, and thus discover underlying relationships. Knowledge of such cause-and-effect dynamics is preserved in as concepts. Not surprisingly, words, one of the ultimate symbols and shapers of abstract meaning, are stored within the semantic memory.
Once written in the declarative memory, experiential and semantic information is not laid out in neat, static lines, but in interconnected web-like networks. The brain by its very structure defines the present by the past, cross-referencing new information with preexisting data in a process of association. It is the highly developed association areas of the cerebral cortex that neurologically distinguish humans from other mammals and even our primate cousins. Within this cortex, external perception, internal thoughts, and emotional triggers are integrated and balanced to create volitional responses. At the heart of this decision-making executive function is the orbital frontal cortex.
Situated behind the eyes and massively integrated into the emotion-mediating limbic system, this specific area not only generates emotive reactions to external perception and internal cognition, but also regulates these responses through inhibition or signal modulation. It is also through the integration of perception, cognition, and emotion that the frontal lobes help to create a coherent and holistic worldview known as a paradigm.
It should be noted that the word paradigm has been badly abused. True paradigm shifts are not trivialities like new business models, but rather changes in the bedrock assumptions of how existence works.
The cognitive constituents of a paradigm are concepts, ideas (alternate states or potential changes in the world), and simulacra--simulacra being the autobiographical and muscle memory recall of physical objects and their properties. Tangled webs of interrelated concepts, ideas, and simulacra form sub-maps known as fields of knowledge. Each field of knowledge covers an aspect of the world and gives rise to some understanding of that broad area's dynamics. The overall paradigm that emerges from these fields of knowledge is a worldview and model that influences which aspects of reality a person notices.
In the words of the political philosopher Samuel P. Huntington, we use our paradigms to:
1. order and generalize about reality;
2. understand causal relationships among phenomena;
3. anticipate, and if we are lucky, predict future developments;
4. distinguish what is important from what is unimportant; and
5. show us what paths we should take to achieve our goals.
The world-awareness that a paradigm makes possible is known sapience. Sapience is a tool of unprecedented power and extends our comprehension of possible consequences and potential outcomes into the future, as much as our episodic memories allow us to look back into the past. This has allowed us an unmatched flexibility in fulfilling our survival needs.
To be fully utilized, the world awareness of sapience incorporates an advanced awareness of self: A complex and emotionally driven model that includes assessments of personal capabilities as well as needs that must be satisfied. This requirement for a representation of self gave rise to the neurological machinery of self-image.
The building blocks of this self-image are schema, which are emotional convictions about capability and self worth. The setting of schema is large part of childhood-development. Such convictions are not easily altered or changed, and the lifetime evolution of schema is the core story of personal growth and maturation.
Additionally, self-image is heavily influenced by the opinions of others. Our ancestors evolved in a niche in which their survival was closely tied to their ability to function within a troop or family band, and it may be that the network of mirror neurons that run through the emotional limbic system of our brains play a crucial role in giving the views of others a weighty impact on ones self-image.
While schema are the unique property of individuals, concepts and ideas can be communicated and shared. The rise of syntax-structured language either allowed or accelerated the process of these memes accruing in common bodies of knowledge and values known as culture. Cultures act as repository of such memetic information and aid in passing down concepts and ideas between generations. This process has also allowed concepts to undergo a multigenerational Lamarckian evolution.
Bodies of culture (mythos)in turn helped to generate the material stability and intellectual climate that gave rise to the Logos: a body of empirically derived concepts. The fruit of the Logos, technology, has impacted the development of human thought in part by creating lives of leisure, the likes of which our forebears could have scarcely imagined. No longer burdened by the struggles of day-to-day survival, the dreams, fantasies, and the pursuit of happiness have played an ever-larger role in the lives of the post-industrial world's inhabitants. Where their grandparents were pragmatists who soldiered through lifetimes of limited opportunities, current generations are faced with the temptations, possibilities, pitfalls, and challenges offered by economies of affluence.
This essay is about the ongoing evolution of human thought from its biological origin to the distinct religious and secular paradigms that have arisen during its course. It also entails an examination of emotion, as cognition and feeling are inextricably linked in the processes of thought. Emotions in a sense are the weight of thought, as situational external awareness, concepts, ideas of risk and potential outcomes are weighed against one another in the processes of decision making. Understanding thought also means understanding the nature of the brain, and so we will first examine the organ of thought and the evolutionary forces that shaped it.
Evolutionary factor 1: Choosing what to eat
The status of our ancestors as omnivores has played a central role in the physical and mental evolution of humankind. Our ability to choose between a wide variety of plants and prey animals presents us with an array of troublesome decisions summed up in Dr. Paul Rozin's famous phrase, the omnivore's dilemma. In short, where dedicated carnivores and herbivores spend little if any mental energy on deciding what to eat, omnivores such as humans are confronted with a wide array of potential victuals, some of which are nourishing and in times of scarcity may make the difference between life and death. Or, these foods might be toxic and lead to painful debilitation or death.
Life as an omnivore calls for analytical intelligence, a keen pallet to detect possible toxins, and a prodigious memory to recall what can and can not be safely eaten. In humans it may have also favored the evolution of language instincts as a means of sharing information on both the availability and safety of food types. As Michael Pollan points out in his book, The Omnivore's Dilemma, cultures act as repositories of food lore, often encoding warnings into the very names of lethal foods, such as the "death cap mushroom."
In addition to the choices offered by an array of potentially edible fungi and plants, the ability to eat meat shaped the evolution of our brains. Acquiring calorie-rich flesh, whether from hunting, scavenging, or cracking open bones with basic stone tools to access the nutrient-rich marrow, allowed for the survival of individuals with larger, calorie-intensive brains, as well as supplying a steady source of the vitamin B-12 essential for the functioning of the brain and peripheral nervous system.
Evolutionary factor 2: Emotion and reason arose from the body and remain interwoven with one another
We experience our emotions in the body, and even the rational intellect's operations are expressed physically, whether in a sense of frustration when attempting to solve difficult problems, a sense of satisfaction upon resolution, or the intense thrill that accompanies a moment of profound realization.
This is because emotions evolved from bodily feelings.
Well before it could reason, a major function of the mammalian brain was to generate behaviors that would sustained homeostasis (thermal and chemical equilibrium within the body). Such behaviors were encouraged by intuitive representations of internal body states such as the feelings of hunger, cold, and want. As the brain became increasingly sophisticated in depicting the external world and more capable of generating models of possible futures, it used bootstrapped versions of these intuitive body-state representations to create a finer motivational matrix. Such upgraded and nuanced bodily feelings are our present day emotions, which more often than not drive us to behave in ways that further the body's short-term prospects for maintaining homeostasis.
Not surprisingly then, the brain is tied into its needy body to high a degree, and the brain-body organism constitutes a massively complex system of constantly shifting feedback loops. In other words, those areas and systems within the brain that play major roles in regulating the body's homeostatic biochemical processes are very much linked to the areas and systems that generate emotions as well those responsible for conscious, rational thought. The biological regulation of the body heavily shapes emotion and reason, just as emotion and reason in turn often influence the body's chemical operations.
As a means of generating behavior, emotion governs memory. The emotion-mediating limbic system encodes our autobiographical memories based on emotive weights. In other words, the more emotional the event, the more likely it is to be remembered over the long run. Encoding memory based on emotion also serves as a means of mapping emotional motivations on to the objects and phenomena of the external world. The physical world that we perceive is a landscape embedded with emotional reactions that provide us the drive to ignore or to focus on phenomena that we encounter. This associative emotive landscape is known as a salience map function.
Evolutionary factor 3: The body is the brain's topic of representation
In addition to creating emotional responses to internal states and external representations, the brain also models of the placement of the body in relationship to objects around it, as well as the position of the body's limbs relative to each other. In essence the body is also the brain's physical frame of reference as well as topic of representation. We exist at one time, in one place, and experience external events from a single, limited point of view. This most fundamental of facts shapes not only how the brain generates its maps of external reality, but also the mind's attempts to overcome these epistemological limitations.
 The brain's parietal lobe—which appears to orients us in space and time—may play a key role in shaping this consciousness. One of its roles appears to be the filtering of internal information from the continuum of sensory inputs. From there, the brain appears to use specific sets of neural pathways to process information that has been tagged as referring to the self. Information pertaining to other humans and objects within the environment travels though a different set of processing paths. A seizure of the parietal lobe has been cited as one possible biological explanation for the mystic's experience: a state of consciousness in which the barriers between self and the universe are dissolved, and the subject experiences all of existence as an undifferentiated unity.
 This system of memory--essentially currents flowing between sets of neurons—may have first evolved so that an object or a threat would not vanish from awareness the moment it passes out of direct sight or hearing.
 Procedural memory appears to be stored within the hippocampus, the declarative in the more recently evolved cerebral cortex.
 Procedural memory may provide clues to individuals whose ability to create new autobiographical memories has been destroyed by neurological trauma, as happened with the fictional protagonist of the film Memento. Dr. Oliver Sachs describes a real-life patient who had also been left unable to recall anything in his life after the removal of a brain tumor, in the story "The Last Hippy." After several years in a hospital, the sheer familiarity for moving around the ward—perhaps captured by procedural memory—allowed the patient to recognize that he had been there for some time as well as recalling the names of those whom he frequently interacted with. Oliver Sachs, An Anthropologist on Mars (Alfred A Knopf, Inc, 1995).
 Interestingly, this area appears to exhibit a great deal of variation between individuals, both in humans and in other primates.
 The limbic, anterior cingulate cortex plays a crucial role in supplying motivation. Patients with damage to this area display little or no signs of volition, and those who recover from injuries in this cortex report having experienced an utter lack of motivation to take self-initiated action or respond to events around them. In the words of neurologist Antonio Damasio the anterior cingulate cortex is a location within the brain where "…the systems concerned with emotion/feeling, attention, and working memory interact so intimately that they constitute the source for the energy of both external action…and internal action…." Antonio R. Damasio, Descartes' Error: Emotion, Reason, and the Human Brain (Penguin Putnam, New York, New York, 1994), pgs, 71-74.
The inhibitory/modulation processes are a function which can obviously be impaired by alcohol or various narcotics. Also, some neurologists classify the orbital frontal cortex as a part of the limbic system.
 This should not be taken to mean that the orbital frontal complex is the site of our awareness or consciousness. Memory is distributed in various regions of the brain, and sensory information is processed in discrete cortices. Awareness may be a series of synchronized parallel process which generate simultaneous representations of external events and internal states. As such, consciousness may arise from cross talk between the various cortices and nuclei which are active within such a representational process. These representations in turn, may be composed of patterns of potential within circuits of neurons, which when fired as a group cause a sensory cortex to generate or reconstitute an image or sensation. Or they can cause physical movement by activating a motor cortex. These depositional representations are proposed by neurologist Antonio Damasio in his book, Descartes Error: Emotion, Reason, and the Human Brain, pgs. 94, 102-105
 The need for self image may have also given rise to the internal narrative voice heard within ones mind. Or this inner voice may have been a means of harnessing the spoken to word to serve as a medium of thought, creating an unprecedented power to solidify vaguely sensed abstracts into concrete concepts. One explanatory hypothesis for schizophrenia is that the internal voice of the mind is a fusion of several sub-voices that represent the various functions or inputs of awareness. The breakdown of a timing mechanism may cause the various sub-voices to fall out of sync, thus creating a perception of the component voices as irresistible or near-irresistible external speakers, despite having an internal origin.
 Mirror neurons fire when an individual observes the actions, expressions, or experiences of another, causing the watcher to experience an echo of the observed person's emotion or physical sensation. Such a sympathetic experience may help in creating emotional interpersonal bonds, as well as with imitating performed actions, and play a role in self-contemplation. As one scientist notes "…mirror neurons may enable humans to see themselves as others see them, which may be an essential ability for self-awareness and introspection." Broken Mirrors A Theory of Autism, Lindsay M. Oberman and Vilayanur S. Ramachandran (Scientific American Reports: Special Edition on Child Development, September 11, 2007) pg. 25.
 Various troops and bands of monkeys and apes appear to develop unique bodies of grooming practices, social gestures, and forging techniques. Thus it can be argued that culture in predates both humans and syntax-structured languages. Early primate memes were passed on by imitation and non-verbal instruction rather than the spoken word. Additionally, language as we know it may have evolved out of a combination of gestures and cries.
 Lamarckism is the idea and an organism passes on characteristics to its offspring acquired during its life time. An example of this is that if an animal builds strength through exertion, it will pass this strength genetically to its progeny. While widely discredited in modern, neo-Darwinian evolutionary biology, Lamarckism has enjoyed something of a resurgence when applied to memes, in that these mental replicators are actively modified by the thinkers who hold them, and then passed along thus changed.
 Among other physical traits shaped by our place as omnivores are our jaws and teeth, which allow us to process both plants and meat. Additionally, the taming of fire may have allowed the intestines and jaws of our ancestors to shrink considerably, as we no longer needed such muscular mandibles and extensive guts to process an all-raw diet. Our largely vestigial vermiform intestinal appendixes appear to be a non-functional holdover from their era of larger intestines, which may have allowed our ancestors to digest uncooked leaves. Individuals born with out appendixes suffer no ill effects or drastically reduced digestive capabilities. The taming of fire also affected our species' development by vastly expanding the amount of plants and animals that could be eaten, as cooking broke down many of the toxins, bacteria, and structural features that prevented us from consuming many types of flora and fauna. Finally, the reduction of the jaw its extensive infrastructure of tendons and anchor points, may have been key in allowing our foreheads to expand, becoming less slopped in order to accommodate a large cerebral cortex.
 The most famous example of the impact of a single-food, low-thought diet is that of the koala. These mammals apparently went from eating a varied diet, to dinning exclusively on eucalyptus leaves. As a result, natural selection worked against the species' large, calorie intensive brains, resulting in a congenitally atrophied, minimalist brain, which occupies only 60% of the cranial cavity--the rest of the skull's internal volume being filled with fluid.
 The brain communicates with all portions of the body via the peripheral nervous system, as well as the blood stream, which transports hormones and neurotransmitters in both directions between the brain and body. Part and parcel of the peripheral nervous system, the autonomic nervous system strives to maintain chemical homeostasis by regulating processes such as digestion, heart rate, pupil dilation, perspiration respiration rate, salivation, and sexual arousal.