#51. A Theory of Christianity [Evolutionary Psychology, Population]

EP     PO     

Red, theory; black, fact.

My gut told me that there is more to be said about Christianity than what I wrote or implied in Post #50. My doubts about the completeness of my work began with this statement by Saint Paul:

“And if Christ be not risen, then is our preaching vain, and your faith is also vain.”

1 Corinthians 15:14, KJV

I was struck by the clarity and insistence of this impossible claim. What is going on here? We as theoreticians need to drill down here.

“Risen” means having come back from the dead, which is still an impossibility for modern medicine. However, Paul explains that what dies is a “natural body,” whereas what rises, or is “resurrected,” is a “spirit body,” which is “incorruptible.” The word “resurrection” does not appear in the Old Testament (Hebrew Bible), making its first appearance in Matthew, the first book of the New Testament. All things considered, the concept is obviously central to Christianity.

Postulate 1: Resurrection theology is an approximate theory, and as such, is allowed to contain an impossibility.

Postulate 2: Christianity is focused on taming a third stage of depopulation that follows the anger cycle and the sadness cycle if neither of these has returned population density to the reset value after a certain time (See Post #50 for explanations of these terms.). This is the total war stage, and it takes place on an international scale. Examples are WWI and WWII, which would be the international phases of national conflicts between a central-European majority and Serbs and Jews, respectively. Total war is arguably altruistic because each of two alliances or countries is helping the other with their population problem. The required signaling cycle seems to be that of the anger cycle but with the exchanged signals doing double duty as liquidation tactics. This is not just a fight, where the only consideration is what would be the shrewdest blow; there is a strong tendency to ape the opponent’s latest gambit, as expected in an exchange of signals "designed" to lock non-altruists out of the process. This psychology is called “sending back the bullet” in battlefield situations and “poetic justice” in everyday life. It is satisfying and it is a signal and it is illegal in peacetime, no matter that the other guy started it. In peacetime, you have to search elsewhere for your solutions than in mimicry and cooperation with a dangerous emotional program.

Furthermore, if you allow yourself to be drawn into a vendetta, you just wrote an “ = “ between yourself and the person you take exception to.

05-06-2022: The old, skeptical explanation of the resurrection, namely that the crucifixion was a fraud, deserves mention here. The New Testament mentions particular Romans and Pharisees sympathetic to Jesus. Extrapolating, I posit a pro-Jesus faction spanning all segments of that society and including many influential Romans and Pharisees, who would have had the resources necessary to pull off such a deception, but who could not openly interdict the crucifixion for lack of the necessary influence. Thus, the seeming miraculousness of the resurrection would in reality be a measure of the power of the illusion that groups identified as “The Enemy” are implacable and unitary. 

The total war program is well known for its destructiveness to the infrastructures of civilization, which suggests that the program evolved recently and is still being refined by natural selection. It may not even be older than agriculture, the last quantum leap in our ability to increase our numbers. That new ability may have generated the selection forces that brought forth the total war program.

Christian theology works a rational override on the anger cycle (See Post #41) by reassuring believers that they will be resurrected and therefore need not fear death. Since anger is fear in disguise, this reassurance undercuts the anger-cycle-like dynamics of the total war program.

Postulate 3: the corresponding exact theory of Christianity is that depopulation events always leave survivors and Christianity enhances your probability of being one of them. When population density has declined to the reset value, this should trigger a dramatic turnaround in the Zeitgeist from death-producing attitudes to nurturing ones, to start the population-density curve on its next long, slow upward climb. The resurrection of “spirit bodies” may refer to the re-establishment of life-valuing attitudes in Society.

03-25-2019: It follows that the human race is being selected for a predisposition to Christianity, and probably other religions as well.

The book of Revelation, the last book in the New Testament, appears to describe the sudden depopulation event that ends the population-density cycle. This is wrongly identified as the end of time/history, but remember that we deal here with an approximate theory.

Christian worship activities revolve around the Eucharist, a communal sharing and consumption of bread and wine. Its purpose is to eradicate the deepest roots of the fear of death, a fear that leads to the hatreds of the total-war emotional program. How does it work?

The Eucharist pacifies people by exposing them to the halting signal of the total war program. So, it halts. How did the consumption of bread and wine come to be the halting signal? Because they are made by people “playing with their food,” for the sake of variety, one imagines. However, this comes at the cost of caloric content (not caloric density) because the yeast always takes its cut. This practice will only make sense under conditions of plenty, which return with sufficient depopulation. Thus, alcohol (which I assume to be the active signaling ingredient) and leavened bread now signal to the human limbic system the return of abundance. I conjecture that these signals have a subtle pacifying effect, making it easier to resist tit-for-tat total-war signalling.

03-02-2024: Alternatively, Jesus may have been medicating the disciples with food and alcohol to keep their arousal level out of the panic zone at a time of peak emotion so that they could continue to function adaptively.

#50. A Naturalistic Theory of Worship [Evolutionary Psychology, Population]

Anytown, Canada, Apr. 11.

EP     PO     

Red, theory; black, fact.

Preamble

As discussed in Post #48, religion has a theory part and an applied part. I have termed the latter the ‘pragma’ of religion, which is basically the modes of worship. Since our moral codes are held by at least the Abrahamic religions to be commands from God, it would follow that it’s pretty important to conform to them, and most of us have difficulty doing this all the time. To help us, religion has developed a behavior-modification role, the role of the pragma.

The behavior-mod role aims at mitigating the human form of the Calhoun Effect–a tendency to aggression linked to rising population density but not to actual want per se. (For an introduction to Calhoun's research, see paragraph 7, Post #37.) Population density would have been an issue even millennia in the past when the world population was a minuscule fraction of what it is today, when people began living continuously inside walled cities for protection from their enemies. Within the inflexible confines of such a city, you have the makings of a human Calhoun experiment. Not coincidentally, the city of Jerusalem, sacred to three world religions, was a walled city. Nowadays, at a world population of 7.5 billion, it can be said that the world is our walled city. What can religion now tell us about how to get along?

I focus here on the Abrahamic religions: Judaism, Christianity, and Islam, which developed in that order, all in the Middle East, each of the last two acknowledging its debt to the previous. I suggest that these three religions form a series of progressively increasing effectiveness in mitigating the Calhoun Effect, by an accumulation of folkloric knowledge. Thus, to see how pragma works, the purpose of this post, we need only examine Islam, likely to represent the most efficient solution. Form generally follows function most transparently at highest efficiency.

The Human Calhoun Effect

In Post #40 I surmise that the natural human population density plot over time has a saw-tooth form, with linear increases alternating with abrupt decreases that return population density to some repeatable reset value. In Post #2, I surmise that the linear segments are created by a negative-feedback controller in the limbic system that controls rate-of-change of population density to a constant positive value, not absolute density. At this writing, the world is probably coming to the crest of one of these linear segments, which began in 1950. The sudden population-density decrease that ends the cycle is conjectured to have two phases: a first phase that produces population-density decrease by emigration, and a second phase that produces population-density decrease by mass murder, if the first phase does not take the system all the way to the reset value. The first phase accomplishes the biological function of dispersal, which is generally important for long-term species survival. The second phase guarantees overall stability on a multi-cycle time scale and wards off Malthusian catastrophes.

Both phases demand formally altruistic acts from individuals, but not of the warm-and-fuzzy kind. The first phase uses an exchange of anger signals (The “anger cycle,” see Post #41) to lock non-altruists out of the process so that the behavior is stable over evolutionary time. The second phase locks out the non-altruists using an asymmetric exchange of signals: contempt signals going one way and sadness signals going the other way. (See “The Sadness Cycle,” Post #41). The second phase culminates in the mass murder of the sadness signalers by the contempt signalers and the appropriation of all the resources of the sadness signalers by the contempt signalers. The last step guarantees that the contempt signalers will appear atrociously entitled to those outside the cycle.

Islam

Islam is conveniently summarized for our purposes as The Five Pillars of Islam, which are explained in the Quran, namely:

1) The Creed. (“There is no God but Allah, and Muhammad is the messenger of Allah.”)

2) Prayer.

3) Charity. (Concealed almsgiving is preferred.)

4) Fasting.

5) Pilgrimage.

The Theory

The creed is “The Great Why in the Sky” that people need for the control of their most difficult emotions. Strong emotion can be overridden by reason if that is required by a learned worldview, the validity of which the person is willing to bet their life on. (Here, I attempt to supply a worldview based on evolutionary psychology.) The creed, or “theory part” of a religion, also gets the rational mind cooperating with the behavior-modification program, which acts on the emotional self. 

04-03-2019: Rational override based on some creed may begin the work of extirpating someone's anger or sadness cycle, but behavior modification by pragma may be necessary to finish it and produce a lasting improvement in the person's circumstances. These cycles may have deep roots inaccessible to consciousness and capable of perpetuating self-defeating behaviors if not treated appropriately.

Prayer superficially is a deliberate wasting of time, which is not free in metabolic terms because the worshipper has a basal metabolic rate that must be supplied whether he/she works or not. Regular inactivity is surely a luxury of only those enjoying abundance. This is implicitly saying to the anger and sadness/contempt programs: “Food is still plentiful, so it’s not time to get nasty.” These cycles may be triggered by signs of high population density, not actual want, but they should still be sensitive to metabolic signals that speak to whether actual scarcity exists. High population density acquired its potent psychological effects, after all, because it usually predicted scarcity in the environment of evolutionary adaptedness. <06-14-2021: Alternatively, prayer may work like meditation to turn off the internal voice and the unnecessary stress it causes (if unscripted).>

Charity, on the receiving end, that is, is for contempt signalers, who, as you will recall, are extremely entitled in the final stage of their emotional program. Accepting charity–goods that you did not work for–tells the contempt program that it has achieved its mission and can therefore halt. So, it does. In Islam, almsgiving is said to be best done in secret, an effect of which will be to spare the pride of the recipient. One tends to think that this will be an issue with contemptuous types. Clearly, we are dealing here with someone whose contempt-signaler role has caused them to become downwardly mobile.

Fasting–going without the necessities of life–is for sadness signalers and it tells their emotional program that they have given or lost all their resources to the contempt signalers, and therefore their program has achieved its mission and can halt. So, it does. <11-21-2020: On the other hand, based on my own experience with fasting, the practice may work by increasing the faster's energy level post-fast, and an increased energy level can solve a multitude of problems.>

Pilgrimage is where you tell the anger-cycle program (with your feet) that you have been driven out of your homeland forever and must resettle elsewhere. Therefore, the program has achieved its mission and can halt. So, it does. This idea was expressed as “giving something to the dispersal drive” in Post #35.

Thus, the task of much religious behavior-modification can be likened to persuading a devil to depart by showing him false evidence that he has accomplished his purpose in coming, knowing that he is myopic. However, prayer tells him that he doesn’t even have to come in the first place.

 (05-23-2024: The tree is gone, apparently a victim of urban buildup. The nearest present-day address may be 179 Clarence, Ottawa.)

#49. The Reentrant-pathway Theory of Mental Illness [Neuroscience]

NE

Red, theory; black, fact.

This theory is a further development of post #45, “The Denervation supersensitivity Theory of Mental Illness.”

The basic idea here is that if a region of cerebral cortex is overgrown relative to a major synaptic partner, not only will it be starved of synaptic input from the partner, but it will also produce excess axons going to that partner that will have difficulty finding enough dendritic territories on which to synapse. Both difficulties can be solved at one stroke, however, if the overgrown area synapses on itself. The logic is similar to the application of valence rules in chemistry.

This mode of repair will produce cyclic signaling pathways (called “reentrant” in Neurospeak) that could support endlessly circulating neural activity. This is therefore an alternative way of getting what I have called “autonomous activity” from disregulated cortical growth, with no need to invoke the phenomenon of denervation supersensitivity. The loop circumnavigation time would have to be long enough to allow for the recovery of any refractory periods that may follow nerve-impulse firing.

The autonomous activity will give rise to hallucinations (called psychotic symptoms) if the re entrant pathway is in sensory cortex, and to manic behavior if in cortex with decidedly motoric functions, which would include planning. Since I have conjectured in these pages that an emotion is a high-level motor command, a re entrant pathway in frontal limbic cortex would produce an apparent emotion disconnected from conscious experience and if in posterior limbic cortex, a hallucinated emotion trigger.

The situation is very similar if a cortical area is normal in size but one of its main synaptic partners is reduced in size by disease. In epileptogenesis, the post-damage remodelling of the local neural networks is known to be associated with new-synapse formation and the sprouting of axon collaterals. The hyperexcitable brain tissue responsible for triggering seizures is known to lie just outside the dead core zone of the damaged region, and can therefore be called “overgrown” relative to the dead zone, which has zero functioning neurons.

All this is compatible with the formation, during the epileptogenesis latent period, of a pair of counter circulating, polysynaptic “ring roads” around the perimeter of the damaged area. This process would be determined by simple rules of valency satisfaction. Both ring roads would be capable of carrying autonomous activity that progresses to a seizure. This might only happen if inhibitory tone is also compromised. Hallucinations and seizures seem to be different grades of the same phenomenon.  Indeed, auditory hallucinations commonly occur in association with temporal-lobe seizures. The temporal lobe is the location of the auditory cortex (Brodmann areas 41 and 42).

#48. Science and Proto-science [evolutionary psychology]

EP

Red, theory; black, fact.

Why does religion continue to be so popular in today's supposedly enlightened age? In what category of things should we place religion for purposes of analysis? This is a very important question. The least bad answer that I have come up with is: "Religion is the last protoscience." (By this I mean "classical protoscience"; a contemporary field of study, string theory, has also been labelled "protoscience," a result I base on a DuckDuckGo search on "Is string theory a protoscience?" on 20 Feb, 2022.)

Protoscience is most easily defined by a few well-known examples: alchemy and astrology. These disciplines can be thought of as crude, primordial versions of chemistry and astronomy, respectively, and unable to quickly divest themselves of laughably bad theories, due to an over-reliance on aesthetics as a way to truth.

If religion is a protoscience, that then, is the corresponding science? Will religion someday transform into some kind of super-science, marvelous beyond all prior imagining, and capable of robustly duplicating all the miracles of Christ, just for starters?

08-03-2020: Formerly at this location, now deprecated: Religion is the protoscience of origins and Darwin's theory its successor via the clergyman Malthus. Malthus was one of Darwin's influences, as attested explicitly in the writings of the latter.

07-26-2020: The science that could replace the protoscience religion is likely to be the study of adaptive, distributed, and unconscious behavioral effects in human populations. <07-30-2020: This will be a division within sociobiology focused on human swarm intelligence acting on an historical time scale.> From my own examined experience, I have reason to believe that such things exist. I called them "macro-homeostatic effects" in the post "The Drill Sergeants of the Apocalypse."

Alchemy is thought to have become chemistry with the isolation of oxygen in pure form by Priestly, followed in short order by its recognition as an element by Lavoisier, who had met Priestly in Paris and learned of the new "air" direct from the discoverer. This clue led Lavoisier to a correct theory of the nature of combustion. Priestly published his discovery of oxygen (Lavoisier's term), which he called "dephlogisticated air" (an alchemical term), in letter form, in 1775.

06-28-2019: The corresponding intellectual hand-off from astrology to astronomy seems to have been from Tycho Brae (1546-1601), who seems to have been much involved with astrology, to his onetime assistant Johannes Kepler (1571-1630; "The Legislator of the Heavens"), who derived three famous mathematical laws of planetary motion from Brae's data.

While the former astrology continues to this day as basically a form of amusement and favorite whipping-boy of sophomores everywhere who are just discovering the use of their brains, and the former alchemy has utterly perished (as theory, not practice), religion continues to pay its way down the time stream as a purveyor of a useful approximate theory.

An approximate theory is useful to have if all you need is a quick and dirty answer. The theory that the Earth is flat is an approximate theory that we use every time we take a step. The corresponding exact theory, that the Earth is spherical and gravitating, is only needed for challenging projects such as travelling to the moon.

03-13-2020: Thus, the God hypothesis is the theory of natural selection seen "through a glass darkly." However, the experiences contributing to the formulation of the God hypothesis would have been due to any cause of seemingly miraculous events over the horizon or beyond the reach of individual memory. This would comprise a mixture of the fastest effects of evolution and the slowest effects of synaptic plasticity/learning (e.g., developmental sensitive periods). However, the capacity for learning is itself due to natural selection and learning is, like natural selection, a trial-and-error process. Thus, the two sources of biological order hinting at the existence of God should usually be pulling in the same direction but perhaps with different levels of detail. Modern skepticism about religion seems to be directed at the intellectual anchor point: the God hypothesis. Since I believe that they are best de-faithed who are least de-faithed, let us simply shift the anchor to natural selection and carry on.

I think it premature to abandon classical religion as a source of moral guidance before evolutionary psychology is better developed, and given the usefulness of approximate theories, complete abandonment may never be practical. However, in our day, humanity is beset with many pressing problems, and although atheism appears to be in the ascendent, it may be time to reconcile religion with science, so as not to throw out any babies with the bathwater.

The modes of worship in use in many modern religions may well confer psychological benefits on the pious not yet suspected or articulated by mainstream science. Scientific investigation of the modes of worship that many religions have in common seems in order, especially since they amount to folk wisdom, which is sometimes on the money. Examples of common practices that seem to have potential for inducing neurophysiological changes are prayer, fasting, pilgrimage, incense-burning, and even simple congregating.

Photo by JJ Jordan on Unsplash

#47. Body-mod Bob's [evolution, evolutionary psychology]

EV     EP     

Red, theory; black, fact.

In the previous post, "Goddesses of the Glacier," evolution appears to be operating in cooperation with a general capacity for technology. Natural selection operates on the brain pathways underlying our aesthetic preferences concerning our own appearance and that of possible reproduction partners and then a technology is automatically developed to satisfy them.

As a first example, consider the oil and brush technology previously assumed for differentiating women from men by hair smoothness. A further step in this direction is to posit that hair color may have been used to code gender. The first step would have been selection for a blond(e) hair colour in both women and men. Since this is a very light colour, it will show the effect of dyeing maximally. Concurrently with this, the aesthetic preferences of men and women would have been differentiated by selection, resulting in blonde women who experience a mild euphoria from being blonde and blond men who experience a mild dysphoria from the same cause. The men would predictably get busy inventing hair-dyeing technologies to rectify this. The necessary dyes are readily obtained from plant sources such as woad and walnut shells. The result would be an effective blonde-female/nonblond-male gender code.

This style of evolution could be very fast if the brain pathways of aesthetic preferences require few mutations for their modification compared with the number required for the equivalent direct modification of the body. Let us assume this and see where it leads.

Faster evolution is generally favored if humans are typically in competition with other species to be the first to occupy a newly possible ecological niche. Such niches will be created in abundance with every dramatic change in the environment, such as a glaciation and the following deglaciation. Possibly, these specific events just slide the same suite of niches to higher or lower latitudes, but the amount of land area in each is likely to change, leading to under-capacity in some, and thus opportunity. These opportunities will vanish much faster than evolution can follow unless a diversity of phenotypes is already present in the prospective colonizing population, which might happen as a result of genetic drift in multiple, isolated sub-populations.

If technologically assisted evolution has general advantages, then we can expect its importance to grow with increases in the reach of technology. Today, we seem to be at a threshold, with male-to-female and female-to-male gender transitions becoming well known. Demand for this service is probably being driven by disordered neural development during fetal life due to contamination of the fetus by environmental pollutants that have estrogenic properties (e.g., bisphenol A, PCBs, phthalates, etc.). The result is the birth of individuals with disordered and mutually contradictory, gendered aesthetic preferences, which is tragic. However, it is an interesting natural experiment.

With further development of cell biology in the direction of supporting body-modification technology, who knows what bizarre hankerings will see the light of day on demand from some customer? Remember that in evolution, the mutation comes first, and the mutation is random. Predictably, and sadly, most such reckless acts of self-indulgence will be punished by reduced employability and reduced reproductive success, doubtless exacerbated by prejudice on the part of the normal, normative majority.

However, the very occasional success story is also to be expected, involving the creation of fortuitously hyperfunctional individuals, and thus the technologically assisted creation of a new pre-species of human.

If the engineering details learned by the body-modification trade during this process are then translated into germ-line genetic engineering, then a true artificial humanoid species will have been created.

After the Pleistocene, the Plasticine.

Photo by Дмитрий Хрусталев-Григорьев on Unsplash

#46. The Goddesses of the Glacier [evolutionary psychology]

Sorry, not found on Unsplash. (Spirits are flying in bearing mukluks and a parka.)

EP

Red: theory; black, fact.

This post is about long hair, of all things (which I totally dig; I was in high school during the Sixties and the girls looked like Shetland ponies), and I will argue that humans evolved the trait to keep them warm during geologically recent continental glaciations. (Please pardon the teleological phrasing; I use it here only for the sake of brevity.)

Can having long hair really confer such a benefit under cold conditions? The anecdotal evidence supporting this idea seems abundant. For example, go to the site shown below

for a near-unanimous list of affirmative replies to the question: ‘Does long hair keep you warm?’ One respondent in particular (#32), from Sweden, seems to have exactly reproduced the method for ensuring this that must have been used in eras of glaciation, assuming that our distant forbears could at least make themselves simple parkas out of animal skins.

They would have supplemented this protection by tucking their long hair down inside the parka. Leaving it outside would have been good fashion but bad engineering, since the locks would have been quickly parted by the first gust of wind and precious, life-saving body heat lost.

I began this with mention of goddesses, but of course the males would have had long hair too, probably a meter long, in outrageous violation of Sixties cultural mainstream gender expectations concerning hair length. I can still hear my Dad fuming about the Beatles.

I find that this situation suddenly makes better aesthetic sense if you imagine this long hair as tousled in the males and smooth and perfect-looking in the females (and perhaps only in the portion showing above the neckline.) Seen this way, both males and females look gorgeous in the imagination and the aesthetic problem is solved. I call this the "rock-star solution." The females could have smoothed their hair by lubricating it with oil and brushing, and a brush is not hard to make. Meanwhile, the males would only need their fingers for cultivating a charming, insouciant look.

Of course, I am thinking here of Mick and Keith and the guys.

While moderns socially code gender as hair length, this parameter was unavailable to our glaciation-era forebears (the last glaciation maximum occurred 26,000 years ago) because they would have been unwilling to cut their hair, knowing at some level of insight that they needed it for survival and mating success. Therefore, they might have coded gender as hair smoothness as described above. 

I assume that these people were living in some glaciation "refugium," as such terrain is technically called, which is a fortuitously ice-free zone surrounded by continental glacier.

While writing this, I was struck by the amount of detailed information I was able to retrieve from my own aesthetic preferences, some of which would have evolved under stringent, cold-climate conditions to produce mate choices favoring traits with survival value. 

The heart may have its reasons that reason knoweth not, but reason is learning*.

11-26-2019 I have not mentioned beards yet and the main question there is why women do not have them. The answer seems to be that a long beard would interfere with breastfeeding, whereas long scalp hair can be pushed back. Moreover, women have more subcutaneous fat than men, so their thermoregulation problem in a cold climate would not be as severe. (Not to be outdone, my niece insists that she has a beard hair.  Go figure.)

*Based on a famous saying by the philosopher Blaise Pascal.

#45. The Denervation-supersensitivity Theory of Mental Illness [neuroscience, evolution, genetics]

NE     EV     GE     

Red, theory; black, fact.

People get mental illness but animals seemingly do not, or at least not outside of artificial laboratory models such as the unpredictable, mild-stress rodent model of depression. A simple theory to account for this cites the paleontological fact that the human brain has been expanding at breakneck speed over recent evolutionary time and postulates that this expansion is ongoing at the present time, and that mental illness is the price we are paying for all this brain progress.

In other words, the mentally ill carry the unfavorable mutations that have to be selected out during this progress, and the mutation rate in certain categories of mutation affecting human brain development is elevated in modern humans by some sort of "adaptive" hot-spot system. "Adaptive" is in scare quotes here to indicate that the adaptation inheres in changes in the standard deviation of traits, not the average, and is therefore not Lamarkian.

In brain evolution, the growth changes in the various parts very probably have to be coordinated somehow. I conjecture that there is no master program doing this coordination. Rather, I conceive of the human brain as comprising scores of tissue "parcels," each with its own gene to control the final size that parcel reaches in development. (This idea is consistent with the finding of about 400 genes in humans that participate in establishing body size.) All harmonious symmetry, even left-right symmetry, would have to be painstakingly created by brute-force selection, involving the early deaths of millions of asymmetrical individuals. This idea was outlined in post 10.

Assuming that left and right sides must functionally cooperate to produce a fitness improvement, mutations affecting parcel growth must occur in linked, left-right pairs to avoid irreducible-complexity paradoxes. I have previously conjectured in these pages that the crossing-over phenomenon of egg and sperm maturation serves to create these linked pairs of mutations, where the two mutations are identified with the two ends of the DNA segment that translocates. (See "Can Irreducible Complexity Evolve?")

Most of the evolutionary expansion of the human brain appears to be focused on association cortex, which I conjecture implements if-then rules, like those making up the knowledge bases familiar from the field of artificial intelligence. The "if" part of the rule would be evaluated in post-Rolandic cortex, i.e., in temporal and parietal association cortices, and the "then" part of the rule would be created by the pre-Rolandic association cortex, i.e., the prefrontal cortex. The white matter tracts running forward in the brain would connect the "if" part with the "then" part, and the backward running white-matter tracts would carry priming signals to get other rules ready to "fire" if they are commonly used after the rule in question.

Due to such tight coordination, I would expect that the ideal brain will have a fixed ratio of prefrontal cortex to post-Rolandic association cortex. However, the random nature of the growth-gene bi-mutations (perhaps at mutational hot-spots) permitting human brain evolution will routinely violate this ideal ratio, leading to the creation of individuals having either too much prefrontal cortex or too much temporal/parietal cortex. In the former case, you will have prefrontal cortex starved of sensory input. In the latter case, you will have sensory association cortex starved of priming signals feeding back from motoric areas.

Denervation supersensitivity occurs when the normal nerve supply to a muscle is interrupted, resulting in a rapid overexpression of acetylcholine receptors on the muscle. This can be seen as an attempt to compensate for weak nerve transmission with a tremendous re-amplification of the signal by the muscle. Analogous effects have been found in areas of the cerebral cortex deprived of their normal supply of sensory signals, so the effect seems to be quite general.

In cases of genetically-determined frontal-parietal/temporal imbalance, I conjecture that the input-starved side develops something like denervation supersensitivity, making it prone to autonomous, noise-driven nervous activity.

If the growth excess is in sensory association cortex, this autonomous activity will manifest as hallucinations, resulting in a person with schizophrenia. If the growth excess is in the prefrontal cortex, however, the result of the autonomous activity will be mania or a phobia. Depression may originally have been an adaptation to the presence of a man-eating predator in the neighborhood, but in civilized contexts, it can get activated by the unpredictable (to the sufferer) punishments resulting from manic activity. If the mania is sufficiently mild to co-exist with depression, as in type II bipolar disorder, then the overall effect of the depressive component may be like a band-aid on the mania.

The non-overgrown association cortex might even secondarily develop the opposite of denervation supersensitivity as the result of continual bombardment with autonomous activity from the other side of the Rolandic fissure. This could account for the common observation of hypoprefrontality in cases of schizophrenia.