Scientific Understanding of Consciousness
Consciousness as an Emergent Property of Thalamocortical Activity

Evolution of Brain


Consciousness and Evolution

The human brain with its neural network are the legacy of billions of years of evolution — molecular, cellular, multicellular, vertebrate, mammalian, and primate evolution.

All sorts of imperfection attests that evolution is not guided by an intelligent creator, but follows random paths in the struggle for survival. (Dehaene; Reading in the Brain, 5)

Consciousness is an emergent property of the interaction of the neural network with the environment.

The neural network has sensory and memory capabilities, which provide real-time conscious sentience with the environment and, with the synaptic memory capability, reflective conscious sentience .

The neural network functions to provide an internal model of reality to assist the organism in surviving in the environment. Consciousness seems to function as a means to assist the organism in evaluating the sensory data and selecting a propitious course of action.

From an evolutionary perspective, core consciousness came to exist when second-order maps first brought together the representation of the organism modified by perceptual engagement with the representation of the object. Damasio & Meyer; Consciousness Overview, 12)


Consciousness is mediated by neural activity of the brain, which is the result of evolution.

· Civilization and language evolution in the last 10 thousand years (art in caves, 30 thousand years),

· hippocampusModern humans have existed ~70 thousand years,

· Rapid expansion of the cortex – especially the frontal cortex – during the last half-million years,

· Built on ~5 million years of hominid evolution,

· Built on ~100 million years of mammalian evolution,

· Built on ~4 billion years of molecular and cellular evolution.


Evolution has left a distinctive mark on the human brain

· The brainstem structures provide functionality for controlling vital life processes and overall modulatory functions for cortical and limbic system systems.

· The limbic system provides quick response functionality for rapidly-changing environmental challenges.

· The cortex provides more-deliberate responses that provide refined behavior, which augments and modulates social interactions, cognitive interpretations, historical perspective, decision-making, and future planning.


Research study — Evolution of Mammalian Brainhigh-resolution x-ray computed tomography to nondestructively scan tiny fossil skulls of two basal mammaliaforms from the Early Jurassic of China.


Research Study — Basal Ganglia Homology with Arthropod Central Complex


Brain evolution from fish, through amphibians and reptiles to mammals, and ultimately to humans, greatest change in the forebrain. (LeDoux; Emotional Brain, 123)

Evolution has hardwired us to catch a pleasure buzz from a wide variety of experiences from crack to cannabis, from meditation to masturbation, from Bordeaux to beef. (Linden; Compass of Pleasure, 4)

What has enlarged in human evolution is not a random group of areas and nuclei, but an entire circuit. (Gazzaniga; Human, 22)

All mammals have frontal cortex, but for most, its main job is movement control. (LeDoux; Synaptic Self, 179)

Reptilian dorsal general cortex has been regarded as a model for the evolutionary precursor of mammalian neocortex. (Shepherd and Koch; Synaptic Circuits, 28)

Amygdala function established eons ago, at least since dinosaurs ruled the earth, maintained through diverse branches of evolutionally development. (LeDoux; Emotional Brain, 174)

In the Out-of-Africa origins for modern humans, Homo sapiens sapiens first appeared in Africa sometime before 100,000 years ago. Modern humans then dispersed throughout the Old and New Worlds, so that by 28,000 years ago, Homo sapiens sapiens was the only surviving member of our genus on the planet. (Mithen; Hand Axes and Evolution of Consciousness, 284)

General view of brain evolution in which, as areas of the cortex evolved, they are laid on top of the existing circuitry connecting inputs to outputs, and in which each level in this hierarchy of separate input and output data pathways may control behavior according to the specialized function it can perform. (Rolls; Emotion Explained, 403)

Massive expansion of the surface area of the cerebral cortex in humans accommodates many more columns and thus provide greater computational power. (Kandel; Principles of Neural Science, 331)

Neocortex was definitely present in mammals 70 million years ago in late Cretaceous times. (Miller; Human Frontal Lobes, 110)

One of the most marked evolutionary changes underlying the unique cognitive abilities of humans is the greatly enlarged cerebral cortex. (Neocortex Outer Region Subventricular Zone Development)

As organisms evolve, the lateral or outer frontal convexity, which is essential for cognitive functions and intelligent behavior, undergoes greater development than that of the medial and inferior (orbital) surfaces, which is critically involved in emotional behavior. (Fuster; Prefrontal Cortex, 3)

The brain is the product of evolutionary tinkering, where lots of little changes have accumulated over extremely long periods of time. (LeDoux; Emotional Brain, 104)

All evolution can do is look for improvements, not perfection. (Waldrop; Complexity, 167)

Natural selection works by conserving something that works, selecting other devices that can cope with complexity. (Damasio; Descartes' Error, 190)

Evolutionary theory - sources of order in the biosphere may include both selection and self-organization. (Kauffman; At Home in Universe, 25)

Consciousness is about 300 million years old. (Edelman; Bright Air, 123)

Krebs Cycle: -  natural molecular building block developed early in evolutionary history, used by a wide range of species; a basic eight-step metabolic cycle, common to almost all cells that use oxygen, ranging from aerobic bacteria to humans. (Holland; Hidden Order, 69)

Two kinds of nervous system organization that are important to understanding how consciousness evolved:  (1) brainstem, together with the limbic (hedonic) system.  (2) thalamocortical system. Edelman; Bright Air, 117)



· Human brain is the result of natural selection in evolution, not a creationist designer.

· Human capabilities have function – not purpose.

· Functionality that currently exists is a result of natural selection among variations resulting from mutations. No design with a purpose. No designer.

It is important to keep in mind that the brain, along with all other biological structures, are the result of evolution by natural selection. Very intricate anatomical structures and neurological processes are there by SELECTION --  NOT by design. Intricate structures, such as those of the limbic system and its connections with the basal ganglia and cortex started out in multicellular creatures as minute neural filaments, and one-by-one over eons of time the components were selected, and the group and its configuration was the result of the natural selection process.

There are three important components of the natural selection process:

· Genetics DNA stores information about what works and is successful in the environment.

· Randomness – mutations, independent assortment and crossovers in meiosis, and random fertilization introduce variation in the architecture and organization.

· Selection natural selection selects the genetic information possessed by creatures that are successful in the competitive environment.

Keep in mind that when you see an intricate biological structure, it must be an ancient one. An intricate structure such as the limbic system and its interconnections with the basal ganglia and cortex cannot appear suddenly; it must have evolved from microscopic neural filaments in tiny multicellular creatures.

As tiny ancient creatures evolved over eons of time, they would have had thousands of neural filaments stochastically established in a variety of ways. Neural filaments that were intensively used were retained by natural selection. Small bundles of neural fibers gradually evolved over many thousands of generations into the functional nuclei we see today in the limbic, basal ganglia and cortex.

Human Brain retains Amphibian and Reptilian Structures

The human brain did not spring fourth de novo; the basic subcortical structures found in reptiles and amphibians survive and play a role in the operation of the human brain. (Philip Lieberman; Human Language, 100)

Primitive features are shared by the divergent species  descended from ancestral species. (Philip Lieberman; Human Language, 100)

Derived features are ones that differentiate a species from other species that have different evolutionary lineages, though they may share a common ancestor. (Philip Lieberman; Human Language, 100)

Language is one of the derived features that differentiate human beings from closely related animals such as chimpanzees. (Philip Lieberman; Human Language, 100)


Three Evolutionary Demarcations in Brain

Brain structures can be crudely apportioned to evolutionary developments.

· Reptilian Brainstem -- Homeostatic processes and basic survival of the animal dominate the functions of the brainstem areas.

· Mammalian Midbrain -- Limbic system functions with emotion dominate the mammalian areas.

· Human Neocortex -- Forebrain and higher cognitive and emotional processing dominate the human functions.

Anatomical structures of the human brain can be traced from reptiles to primates to humans. Gerald Edelman’s primary consciousness exists in primates and most other mammals.

Prefrontal cortex has expanded the most in primates and may not even exist in other mammals. (LeDoux; Emotional Brain, 177)

The human brain is characterized by the expanded development of the neocortex. The structures of the limbic system, hypothalamus, and brainstem have changed little. (Changeux; Neuronal Man, 115)

Olfactory pathway to olfactory paleocortex may have evolved before thalamus and neocortex. (Sherman and Koch; Thalamus, 325)

Phylogenetic development of the hippocampal formation has demonstrated that it is a form of phylogenetically old cortex, the archicortex, that develops in the medial wall of the telencephalic vesicle. (Andersen; Hippocampus Book, 115)

Three levels of sensory properties in the evolution of animals with neurons: (1) example, Lobster; Responses to stimuli with aversive and consummatory responses; no primary consciousness, (2) example Dogs; primary consciousness, (3) Humans; human-type consciousness. (Edelman; Bright Air, 151)

Consciousness is about 300 million years old. (Edelman; Bright Air, 123)

The original two regions of prefrontal cortex, which are present in other mammals and evolved earlier, are the orbital prefrontal region, which responds to external stimuli that are likely to be rewarding, and the anterior cingulate cortex, which process information about the body's internal state. (Gazzaniga; Human, 21)


Brain stem



Two systems, limbic-brain stem and thalamocortical, were linked during evolution.  The later-evolving cortical system served learning behavior that was adapted to increasingly complex environments. (Edelman; Bright Air, 118)


Fear ----- Pleasure


Nucleus Accumbens


Cognition is a necessary function to provide movement control. The brain functions as a reality simulator. Brain cognitive functions evolved to provide prediction of predator and prey future movement and position.

Value system


Movement control

Biped, walking, freed forelimbs

Thumb, toolmaker

Vocal articulation, speech and language

Sensory Systems

Language evolution

Language evolution provides one way to study human migration and cultural development during the last 10 thousand years.


   Evolution commentary

Life is an emergent phenomenon arising as the molecular diversity of a prebiotic chemical system increases beyond a threshold of complexity. Life is a collective property of systems of interacting molecules. (Kauffman; At Home in Universe, 24)

Emergence of life as an expected property of the physical world. (Kauffman; At Home in Universe, 64)

Krebs Cycle: -  natural molecular building block developed early in evolutionary history, used by a wide range of species; a basic eight-step metabolic cycle, common to almost all cells that use oxygen, ranging from aerobic bacteria to humans. (Holland; Hidden Order, 69)

There may have been more than one Homo species on earth simultaneously during evolutionary history, although not closely coexisting in contact. Neanderthal and Homo sapiens may have coexisted at some time ~40 thousand years ago.

One reference for evolution of the brain. (Eccles, Evolution of the Brain)

The intricate interconnections of the midbrain must have started out eons ago as a developing plethora of randomly formed connections of neural fibers in tiny multicellular creatures that were selected one-by-one over time.

Over eons of time, (1) randomness at each reproductive step, together with (2) massive copy number variations via insertions and deletions, have resulted in a plethora of variations in the organization and architecture of the genetic material.


Natural selection always favors attributes that enhance the survival of our genes, not simply our own personal survival. We die, but our genes may go on forever. (Johnston; Why We Feel, 85)

Genes have a higher probability of being present in close relatives than in distant relatives or strangers. (Johnston; Why We Feel, 85)

Like bodily affects, the positive or negative hedonic tone of an emotion provides the necessary value system for learning to adapt to rapidly changing aspects of the environment. (Johnston; Why We Feel, 86)

Intensity of affects and emotions can be viewed as amplifications of the reproductive consequences of current physical or social circumstances. (Johnston; Why We Feel, 87)

Evolution has provided humans with a primary value system of pleasant and unpleasant feelings. (Johnston; Why We Feel, 106)

Conscious experiences, like sensations and feelings, evolved because they dictated a dynamic organization of the nervous system that could prioritize experiences and distinguish between environmental events or circumstances that had a real influence on biological survival. (Johnston; Why We Feel, 127)

Primary consciousness emerged in evolution when, through the appearance of new circuits mediating reentry, posterior areas of the brain that are involved in perceptual categorization were dynamically linked to anterior areas that are responsible for a value-based memory. (Edelman; Universe of Consciousness, 102)


Simple Nervous Systems

Spider, orb web, innate

No Nervous System





Evolution of the Human Brain

Lateral Prefrontal Cortex, Unique to Primates

The evolutionarily newest region of the prefrontal cortex, lateral prefrontal cortex is apparently unique to primates and is concerned mainly with the rational aspects of decision-making, which are our conscious efforts to reach a decision. (Gazzaniga; Human, 21)

The original two regions of prefrontal cortex, which are present in other mammals and evolved earlier, are the orbital prefrontal region, which responds to external stimuli that are likely to be rewarding, and the anterior cingulate cortex, which process information about the body's internal state. (Gazzaniga; Human, 21)

Orbital prefrontal region and the anterior cingulate cortex, the two original regions of prefrontal cortex work together to contribute to the emotional aspects of decision making. (Gazzaniga; Human, 21)


Duplication, Meiosis, mutation, variation, novelty – Human rapid evolution in brain

(Llinas, 18)

(Llinas, 21)

(Llinas, 25)

Brain development is the major battlefield of the nature-nurture conflict. (LeDoux; Synaptic Self, 65)

Comparative Anatomy

Brain of fish,    basal ganglia (control of movement),    thalamus (relay in pathways going to hemispheres),    hypothalamus (controlling basic behavior, regulating secretion of hormones),    cerebellum (organ of balance) dorsal wall of posterior ventricle.    Fish, highly developed sense of smell, search for food.    Cerebral hemispheres very thin, specialized for olfaction.    Amphibians and reptiles,    similar olfactory center, ventral half of each hemisphere.    Mammals and humans, olfactory center a pear-shaped lobe on lower surface of brain.    In partially terrestrial amphibians and the reptiles, the senses, particularly vision, associate sensing and motion functions in the dorsal parts of the hemispheres.    In humans, it becomes the hippocampus.    Neocortex, projections functions of the sense organs, association functions. (Changeux; Neuronal Man, 43,44)

Diagram showing the expansion of the neocortex from reptiles through a primitive marsupial to man. The most primitive part of the cortex is specialized for olfaction. One primitive area goes 'inside' to form the hippocampus in mammals. Neocortex is small or absent in reptiles. Basal ganglia, ventricles. (Changeux; Neuronal Man, 45)

Number of convolutions, or gyri, increases from almost none in primative animals through the primates to reach a maximum in humans. (Changeux; Neuronal Man, 45)

Same categories of cell are found at all stages of evolution from primitive mammals to humans.    No cell categories are specific to the human cortex.    Categories of pyramidal and stellate cells are the same from mouse to humans.

Cerebellar cortex in higher vertebrates, including humans, contains five types of cells    repeated many times. (Changeux; Neuronal Man, 62)

 (Changeux 50)

(Changeux 45)

(Changeux, 43)

(Changeux, 44)

(Changeux, 45)


Nothing quite like the neocortex exists in reptiles. (Squire; Fundamental Neuroscience, 1154)


 Brain Evolved to Control Movement

Creatures that move have a nervous system or sensory capability to control movement in a dynamic environment.

Brain evolved to command and control intricate movement in a dynamic environment.

Prediction is the ultimate function of the brain. (Llinás; I of the Vortex, 21)

The ability to predict evolved in tandem with increasingly complex movement strategies. (Llinás; I of the Vortex, 25)

Brains are an evolutionary prerequisite for guided movement in primitive animals. (Llinás; I of the Vortex, 18)

Nervous system evolved to provide a plan, one composed of goal-oriented, mostly short-lived prediction verified by moment-to-moment sensory input. (Llinás; I of the Vortex, 18)

Primitive creatures such as ants and cockroaches are biological automatons. (Llinás; I of the Vortex, 202)

Brain function implements what natural selection has found to be the most beneficial in terms of species survivability. (Llinás; I of the Vortex, 202)

Some Emotional Similarity across Vertebrate Species

Neural organization of emotional behavioral systems of vertebrates is similar across species. (LeDoux; Emotional Brain, 107)

Some emotional systems in the brain are essentially the same in many vertebrates, including mammals, reptiles, birds and possibly amphibians and fishes. (LeDoux; Emotional Brain, 107)






Human genome studies

HapMap, haploid genotype, alleles, SNPs.

Copy number variation

Genetics AND Environment

Consciousness and the Self are based on genetics AND environment.

Memes passed on culturally.




Books on Evolution

There are many excellent books on evolution; here are a few that I use:

Johanson & Edgar; From Lucy to Language, -- excellent book by world-renowned experts; plenty of dramatic photographs and lots of informative discussion. A slight caution: the phylogenetic relationships of human evolution are continually being updated as additional fossils are discovered and expert researchers have differing interpretations.

De Duve; Vital Dust, -- here is a discussion of chemical and cellular evolution by a Nobel prize chemist who has interesting ideas about the possible influence of sulfur.

Hazen; Genesis: The Scientific Quest for Life’s Origins – special emphasis on the function of minerals and clays that may have served as scaffolds for primitive biochemical reactions among inorganic and organic molecules.




Link to — Consciousness Subject Outline

Further discussion — Covington Theory of Consciousness