The Burden of the Past in Our Brain: Evolutionary Layers of the Nervous System

Introduction: The Brain as an Evolutionary Palimpsest

Anthropologist Stanislav Drobyshevsky opens by framing the human brain as the cumulative product of the entire history of life, not merely of recent human evolution. Even the dramatic changes visible over the last 25 million years of primate and hominid evolution are trivial compared to the roughly billion-year span of multicellular existence during which nervous systems were shaped.

A Nervous System Is Not Required for "Nervous Activity"

• Many organisms — plants, fungi — solve problems, react to their surroundings, move, and secrete signaling substances (phytohormones) without any nervous system at all.
• This demonstrates that "nervous activity" and "a nervous system" are not synonyms; responsiveness can be achieved by other means.
• Nervous systems arose repeatedly and independently in different lineages (for example, in ctenophores, on a parallel evolutionary branch).

The Long Road of Our Ancestors

Each stage in this sequence left its mark on the nervous system:

1. Free molecules and prebiotic chemical evolution
2. Complexes, then cells, then multicellular aggregates
3. Burrowing, then swimming
4. Fish-like forms; the appearance of jaws, teeth, and a neck region
5. Crawling on the bottom, then emergence onto land
6. Scrambling through coastal thickets and tree-like horsetails
7. Climbing into trees; the whole Mesozoic spent alternating between forest floor and branches
8. In the Cenozoic, becoming true primates — climbing, leaping, and eventually grasping branches
9. Descending from the trees roughly 3 million years ago; about a million years of "unsettled" australopithecine life on the savanna
10. The last ~2.5 million years as humans: primitive tools → advanced tools → religion and science

The Brain as a Nested Doll (Matryoshka)

The core organizing principle: the deeper a structure lies in the nervous system, the more ancient, the more vital, and the simpler it is.

• The earliest reactions were minimal: move toward light, move away from light; a chemical signal means food, another means predator.
• The reticular formation, deep in the brainstem, is a relic of the stage when the nervous system was a diffuse net (like a modern hydra's). "Reticular" literally means "net-like." It governs breathing and circulation — the most basic reflexes.
• Newer layers were added on top as organs and needs grew more complex, culminating in the neocortex.

Important Caveats

• The common division into "three levels" is a convenience and a cultural preference for the number three, not a biological fact; there are many more gradations.
• The same kinds of levels arose independently and for similar reasons in different parts of the brain.
• It is not strictly true that lower structures are primitive and upper/anterior ones advanced: even a lamprey already has the same five brain divisions we do, dating back to Ordovician–Silurian jawless fishes.

Three-Level Architecture Illustrated

The Cerebellum

Level	Structures	Function	Evolutionary origin
Archicerebellum	Certain lobules; the deep fastigial (tent) nucleus	Balance; movement of the tail	Jawless fishes (lampreys)
Paleocerebellum	Interposed/globose-like nuclei	Control of head, neck, trunk; simple paired-limb movement	True bony fishes
Neocerebellum	Dentate nucleus	Complex segmented limb movement (shoulder–forearm–hand; thigh–shin–foot)	Maximal in birds and mammals

• The lamprey is a "fish that isn't quite a fish": no jaws (though it has teeth), no paired fins ever, no true skeleton (only a notochord and hints of vertebral arches), a gill lattice rather than gill arches, and no skull roof. Its only need is to avoid tumbling belly-up — minimal cerebellar machinery suffices.
• In true fishes, paired fins act as rudders and stabilizers, the gill lattice differentiates into arches, and the first arch becomes the upper and lower jaws.
• Birds developed additional cerebellar nuclei for flight and even "think" with the cerebellum to a notable degree; humans do so only slightly — though a bird's "thinking a lot" is still very little by human standards.

The Basal Ganglia (Striatum)

• Septum pellucidum — a thin, unremarkable-looking sheet beneath the corpus callosum that performs basic emotional regulation, such as suppressing aggression.
• Paleostriatum (globus pallidus) — controls unconscious emotional movements: flinching in fright, spontaneous expressive gestures. Deliberate imitation of such movements is produced by the neocortex and is therefore "fake."
  • Emotion in its pure form is essentially fish-like behavior. When films urge viewers to "stop thinking, just feel" — as with Luke Skywalker switching off his targeting computer — the instruction effectively means "be a fish; use your paleostriatum."
  • Tap on a fish tank and the fish dart about: pure emotion. This is highly adaptive, because danger demands instantaneous, reflex-like responses.
  • The claim that emotions are uniquely human is nonsense — animals have emotions but not reason; humans have emotions plus reason.
• Archistriatum — appears in reptiles; often loosely labeled the "reptilian brain," though no literal lizard brain exists inside us. Its amygdala complex, in the tip of the temporal lobe, handles three basics: smell, aggression, and fear, and forms part of the larger limbic system. Chemical detection triggers either attack (if prey) or flight (if one is the prey) — simple, unambiguous, indispensable behavior requiring no thought.
• Neostriatum — the caudate nucleus, claustrum, and putamen; developed in reptiles and expanded in birds and mammals. The head of the caudate suppresses aggression.
  • A key insight: the disappearance of a reaction can be more evolutionarily advanced than its appearance, because suppression represents a later regulatory layer over an existing response.
  • Crucially, this suppression is automatic and unconscious — these are nuclei, not cortex.
  • The neostriatum also stores conditioned reflexes: e.g., after habitually flipping a light switch in one spot, the hand jerks toward the same spot in a different room. This allows learning what cannot be pre-written in the genome.

The Cortex (Pallium)

• Paleopallium — the fornicate gyrus, cingulate and parahippocampal gyri, olfactory bulbs. Handles smell, taste, and associated emotions, including automatic social reactions.
  • This explains the instant, inexplicable liking or disliking of another person — often driven by odor. Whether human pheromones work is uncertain, but odors demonstrably do, usually below the level of conscious articulation.
• Archipallium — the hippocampus ("seahorse") and dentate gyrus. Also olfactory and emotional, but it regulates the overall level of emotionality: damage makes a person flat and "wooden," overexcitation makes them hyper-emotional. It also handles short-term memory — the proverbial "memory like a goldfish," present in bony fishes.
• Neopallium (neocortex) — six-layered, responsible for thinking, consciousness, will, and long-term memory. Present not only in humans but even in monotremes (platypus, echidna, long-beaked echidna), so it existed by the late Triassic and certainly by the Jurassic.
  • Since then human neocortex has grown in volume but not in fundamental structure.
  • Given the trend of increasing complexity from lampreys through fishes, amphibians, reptiles, and early mammals, a future "super-neopallium" with, say, ten layers is hypothetically conceivable — but only if suitable conditions and tasks arise.

Types of Nervous Activity

1. Reflex

An unambiguous response to an unambiguous stimulus in stereotyped conditions, using the minimum number of neurons and muscles.

• Examples: knee-jerk reflex, piloerection (each hair has its own muscle, so hair stands up from cold or fear), pupillary reflex, tracking reflex, blink reflex, jerking a hand from a hot pan.
• Attempting to suppress the knee-jerk as a display of willpower is pointless — and losing the reflex is medically alarming, potentially indicating spinal cord damage.

2. Conditioned Reflex

• Pavlov's classic bell-and-saliva demonstration.
• Humans do form conditioned reflexes, but with more difficulty than other animals, because learning can conflict with them.
• Still involves only a countable handful of neurons (sensory, motor, plus interneurons).

3. Instinct

A stereotyped, learning-independent response, but now a complex sequence of muscular and behavioral acts triggered by a specific stimulus. Most fully developed in birds.

• The goose and the egg: a goose whose egg rolls out of the nest tucks its head down and rolls it back — and cannot do otherwise. It will roll back a wooden or stone egg; if a stone egg is slightly larger than a real one, it will roll the stone first. It cannot decide to postpone the task or hope the egg returns on its own.
• Humans essentially have no instincts, because instincts contradict thinking and learning.
  • An owl puffs up, spreads its wings, and hisses; a cat arches, raises fur, flattens ears, unsheathes claws — always identically.
  • A human instinct of self-preservation would mean every person leaps into a tree when a predator appears. In reality, people variously climb, grab a stick, scream, freeze, run, attack, or call for help — proving it is not instinct.
  • If instinct and learning coexisted they would conflict fatally: instinct commands climbing the tree while learning commands grabbing the rifle, and the person does neither and dies.
  • Instincts remain clear in prosimians and Old World monkeys — stare into a macaque's eyes and the full automatic display unfolds.
• The only identified human instinct is the eyebrow flash upon recognizing another person. Large cross-cultural studies found this to be near-universal. Even this is imperfect: the speaker notes his own eyebrows twitch for strangers and fail to twitch for acquaintances, owing to poor face recognition.
• So-called "maternal instinct," "self-preservation instinct," and "food instinct" are at best predispositions — a phenomenon for which no good term yet exists. If maternal instinct were real, all mothers would care for children identically; in fact many care poorly, inconsistently, or must learn by trial and error.
• Infants do possess genuine reflexes: sucking, grasping, and the Babinski reflex (toes fanning when the sole is tickled). The Babinski reflex is normally suppressed as newer brain regions mature; its presence in adults signals that those regions either never developed or have degenerated.

4. Learning / Reason

Activity that changes over time, incorporates prior experience, engages vast neural networks, transforms experience into ideas, and generates grounded predictions about outcomes.

• This is governed by the neocortex, which by volume exceeds all other nuclei and pathways combined; most pathways run to or from it (though thinking occurs in cortex, not in the conducting tracts).
• Humans: essentially no instincts, only basic fish-inherited reflexes, and learning developed to its maximum.

How the Levels Interact

• Reflexes operate by default and are extremely hard to override consciously.
• Grabbing a red-hot poker: a normal person drops it instantly. Someone "training willpower" can use the neocortex to suppress spinal cord activity and hold on, sustaining severe burns.
• If the neurons register that the behavior is inadequate and potentially fatal, the body shuts down consciousness: the neocortex, behaving inappropriately, is switched off, the person faints, releases the poker, and is saved.

Functional Divisions of the Nervous System

Somatic vs. Autonomic

• Somatic — regulates skeletal muscles, skin, and joints; consciously controllable (one can move the arms deliberately, or forget about the legs entirely and then remember them).
• Autonomic (vegetative) — regulates internal organs, glands, blood and lymph vessels, and respiration; runs by itself. This is the ancient level that operated in lancelets and fishes with only a neural tube and barely any brain.

Sympathetic vs. Parasympathetic

Illustrated by the bear-on-the-forest-path scenario:

• Sympathetic (mobilization of resources) activates instantly upon encountering the bear: heart rate and breathing accelerate, arteries dilate to deliver oxygen and nutrients to muscles, the intestines shut down, salivation stops (dry mouth), pupils dilate to see where to run.
• Parasympathetic (restoration and pacification) takes over after the escape — say, 10 km later: heart rate and breathing slow, peristalsis resumes to digest and restore energy, vessels constrict (the flushed face returns to normal), pupils narrow — until the bear also covers those 10 km and the cycle repeats.
• These systems are anatomically scattered but work in opposition, innervating the same organs with different neurons: some intensifying, others damping.

Pyramidal vs. Extrapyramidal

• The pyramidal system is named because its corticospinal tract passes through the pyramids of the medulla oblongata.
• The extrapyramidal system is named because its pathways do not pass through the pyramids.
• The naming is essentially arbitrary and historical, but convenient in its own way.

The Extrapyramidal and Pyramidal Systems in Practice

Extrapyramidal: Many Small, Ancient Nuclei

• The extrapyramidal system consists of many small nuclei, inherited at least from the level of jawless fishes (cyclostomes), possibly earlier.
• Each nucleus performs its own narrow function: the red nucleus regulates muscle tone, the globus pallidus and amygdaloid complex handle emotional movement, the substantia nigra releases dopamine.
• From each of these elements runs its own private pathway — the rubrospinal tract, the reticulospinal tract, and so on — down to the spinal cord and out through the motor roots of the spinal nerves to specific muscles.
• These pathways govern unconscious, involuntary, automatic movement. While sitting, the back and neck muscles work continuously to keep the body from tipping forward or backward and the head roughly vertical, without any deliberate thought about tensing the long muscles of the back or the scalene muscles of the neck — muscles most people do not even know exist.

Pyramidal: The Conscious Spotlight

• The moment one thinks about posture, the pyramidal system takes over: the neocortex, chiefly the precentral gyrus, which handles conscious movement control. The same muscles are then driven by entirely different neurons.
• A single corticospinal tract carries these commands — one pathway, but larger than all the other motor pathways combined, because the human neocortex is enormous.
• The crucial nuance: we can use it but are not obliged to. At any given moment only a small part of the body is under conscious control — the speech apparatus while talking, the arms while gesturing, while the legs are largely forgotten.
• The best metaphor is a flashlight beam moving across the cortex, illuminating one region at a time: now the hand, now the foot, then nothing at all — during sleep the autonomic system takes over entirely and conscious control shuts off.
• Sustained control of any single function is impossible for long: neurons tire and need time to restore their glucose reserves.
• Training can, however, dedicate more neurons to a specific task. This is exactly what athletes and actors do by consciously drilling the same movement, and it applies to specialized skills such as sign language — untrained hands merely wave randomly; trained ones produce meaningful signs.

What Cannot Be Controlled

• The autonomic system remains outside conscious command: one cannot deliberately contract the stomach, stop the heart, or speed it up.
• Indirect influence is possible via skeletal muscles (compressing or relaxing vessels), and yogis manage some direct influence over peristalsis and heart rate — but this is inadvisable and risky. Deliberate meddling with autonomic regulation invites serious problems. It is fortunate that it runs on its own.

The Diencephalon: A Reservoir of Archaic Structures

The brain has five divisions — medulla, hindbrain, midbrain, diencephalon, and telencephalon. The diencephalon is large and comprises three parts: the epithalamus above, two massive thalami in the middle, and the hypothalamus below. It is often loosely called the "reptilian brain," though it is in fact mammalian and arranged differently in actual reptiles.

The Epiphysis (Pineal Gland): A Former Eye

• Our ancestors had four eyes: the ordinary left and right pair, plus a parietal eye and a pineal eye on top of the head. For a fish's head this was perfectly logical — lateral eyes to see sideways, dorsal eyes to see upward.
• Once vertebrates left the water and became reptiles, looking straight up lost its urgency, and the upper eyes vanished — though their functions partly survived.
• In the iguana, a pale spot on the crown is still externally visible. In the tuatara, though covered by scales, the organ retains a retina, lens, cornea, iris, and even a functioning nerve; it reacts to light much as a frog's eye responds to nearby movement.
• Fossil ancestors — the therapsid "mammal-like reptiles" — often had a parietal opening nearly as large as the ordinary eye sockets.
• Today the epiphysis sits practically at the center of the brain, nowhere near the surface, yet performs largely the same job. Fibers from the optic nerve and optic tract reach it, and it responds to light. The structure changed — the eye became a gland — but the function essentially remained.

Its two main roles:

1. Inhibiting the pituitary, which secretes growth hormone. The epiphysis must suppress it to stop growth. Too much inhibition produces short stature (and, in the extreme, dwarfism); too little produces tall stature and, at the extreme, gigantism.
2. Regulating circadian (daily) rhythms. When sunlight is present, the epiphysis triggers release of serotonin — one of the "happiness hormones" — and we feel alert and cheerful. In darkness, two chemical reactions convert serotonin into melatonin, and we fall asleep.

Circadian rhythms also depend on other factors — fatigue, time zones — and blind people sleep and wake perfectly well; but this is the baseline mechanism.

The Thalamus

A general rule of nervous-system architecture, from spinal cord to forebrain: ventral (lower, belly-side) structures tend to be motor, dorsal (upper, back-side) structures tend to be sensory.

Why: back when we were lancelet-like creatures swimming near the bottom, all trouble came from above — ultraviolet, falling sand, predators. Nothing much threatened from beneath the sand (and if a polychaete worm grabbed you, you were simply eaten and removed from the gene pool). So sensory apparatus concentrated dorsally. Meanwhile, we crawled on our bellies, so myotomes and muscular elements — and therefore motor structures — concentrated ventrally. Chemoreceptors are an exception in position: they sit front and low, because one must smell forward to detect food and predators in advance.

The ventral thalamus was originally motor. In a frog it drives jumping; in a fish, swimming. But when the neocortex and its pyramidal system appeared, this older motor function became largely redundant. It could not simply disappear, however, because it is written into the genome.

• The result: a substantially vestigial organ — a chunk of brain a couple of centimeters across that is, frankly, useless.
• Signals for voluntary movement pass through or bypass it, and there exist known closed neural loops in which two or three neurons pass a signal in a circle indefinitely. The information is no longer needed, but a neuron cannot simply not work, so it cycles the signal pointlessly, wasting energy and time.
• Whether removing this would make us think faster is unknown — the matter is complicated.

The dorsal thalamus is, as expected, sensory, and its layout is strictly logical:

• Anterior nuclei — olfactory (the nose is in front; smell must detect what lies ahead).
• Middle nuclei — touch and joint sensation (proprioception): sensing one's own shape and position relative to oneself and to the planet.
• Posterior nuclei — vision and, to a degree, hearing.

Why the visual centers ended up at the back of the head: originally the eyes sat squarely on top of the head in fishes, directly opposite their brain centers, while the lateral line ran along the flanks (later reduced to the ears and, via clever transformation, the balance organ). When the face became a face, the eyes migrated forward; simultaneously the brain swelled like dough rising out of a pot, pushing the structures that had been on the crown backward. Hence the seemingly illogical arrangement — eyes in front, visual cortex in the occiput — which was originally perfectly aligned.

The Hypothalamus and the Pituitary

The pituitary (hypophysis) is a remarkable structure: originally a gill gland, a pocket of the pharynx, and embryologically derived from endoderm, whereas the brain is ectodermal — yet it contains neurons.

• It has two portions: the adenohypophysis (anterior and intermediate lobes) at the front and the neurohypophysis (conducting fibers) behind.
• It connects to the brain via the infundibulum and the tuber cinereum, but lies outside the brain's membranes — because it was, after all, originally a gland grafted onto the brain, which now performs a humoral (hormone-secreting) function.

The hypothalamic–pituitary system operates by negative feedback:

1. The adenohypophysis releases tropic (triggering) hormones into the blood.
2. These reach the pituitary-dependent glands — thyroid, gonads, adrenal cortex — and switch them on.
3. Those glands release their own effector hormones, which circulate and broadly accelerate metabolism.
4. Reaching the brain, these hormones activate neurons in the tuber cinereum, which release statins.
5. Statins travel down the infundibulum and suppress the pituitary.
6. Tropic hormones stop; the glands go quiet; their hormones no longer stimulate the tuber cinereum, which now releases liberins.
7. Liberins reactivate the pituitary — and the cycle begins again.

Condensed: the more actively the pituitary works, the less actively it works; the less actively it works, the more actively it works. The net result is homeostasis — equilibrium.

When it goes wrong: a skewed system skews continuously in one direction. Failure points are numerous — the pituitary itself (which is complex), the hormones, the hormone receptors, the target gland or a specific part of it, that gland's hormones or their receptors, the nuclei of the tuber cinereum (at least sixty of them), or the releasing factors (statins and liberins). Endocrinologists work on this, but it is difficult; hormones act powerfully, so hormonal drugs must be taken only on medical indication and with great caution. For most people the system works acceptably at least until old age, when everything begins to fall apart.

This entire carousel is extremely ancient — arising at the level of lancelets and jawless fishes — and is entirely beyond conscious control.

Appetite, Feeding, and Our Dietary History

The Feeding Nuclei of the Hypothalamus

Substantial parts of the hypothalamus and tuber cinereum regulate metabolism in the broad sense, including feeding.

• Lateral tuberal nuclei: stimulation arouses appetite. When destroyed in rats (never done in humans), appetite disappears; the rat stops eating and grows thin — but does not die. After a time it resumes eating in three characteristic phases: first only "treats" (by rat standards), then normal rat food without drinking (still losing weight), and finally both food and water — but at a lower consumption level than before the lesion.
• Medial tuberal nucleus: stimulation suppresses appetite; destruction produces ferocious hunger. Lesioned rats eat voraciously, becoming round, glossy, and sleek — though they do not literally burst; other regulators eventually kick in, but at a higher consumption level than before.

The speaker jokes that anyone tempted to poke a needle into their own lateral nucleus to lose weight should not — quite apart from the technical impossibility (in a rat one simply saws open the skull; in a human the nucleus lies at the brain's center, the nearest route being through the nose), one might hit the medial nucleus instead, with the opposite result.

What Our Ancestors Actually Ate

1. Insectivorous from the end of the Mesozoic through the whole Paleocene — we were shrew-sized nocturnal animals, and insects are the best nighttime food: nearly pure fat, protein, and calories. Humans still retain an enzyme for breaking down chitin (lemurs have several; we have roughly one).
2. From about 45–50 million years ago, increasingly plant-eating.
3. By 30 million years ago, decidedly fruit- and leaf-eating, remaining so through the early catarrhines and the first australopithecines.
4. From about 2.5 million years ago, upon entering the savanna, adding meat.

Throughout, we were strictly omnivorous, merely shifting emphasis — sometimes insects, sometimes fruit and leaves, sometimes meat, depending on what could be found, caught, or obtained.

Our closest ancestors — Cro-Magnons and, as indirect ancestors, the Ice Age European Neanderthals — were super-predators, more carnivorous than cave lions. This is hard to exceed, since cave lions eat nothing but meat — but one can also eat the cave lion.

The Simple, Unhelpful Rules Our Brain Inherited

Rule 1 — Eat everything you find, because tomorrow there may be nothing. There were no guarantees; even in a rich Pliocene landscape with abundant prey and few predators, disaster could follow. So when food appears, the brain signals: devour it immediately. The problem is that under modern conditions food does not run out — there is a refrigerator so full its door will not close and a 24/7 shop flashing bright red lights (red, characteristically, because our attention is tuned to it).

Rule 2 — Eat sweet things first, because we were fruit-eaters and glucose underpins the whole metabolism (the Krebs cycle, mitochondrial energy production). Plants synthesize glucose; we eat it and convert it. But in nature pure glucose does not exist — sugars come in various forms whose processing costs energy. Now a whole decorative sugar bowl sits on the table, tempting spoonfuls — and diabetes follows.

Rule 3 — Store everything eaten as fat, because fat is the ideal reserve: stable, and it doubles as thermal insulation. The urge to grow fat is a natural drive of the organism. Decoding the Neanderthal genome suggested they were strongly inclined to obesity — but they lacked the means to realize it. We have the means, and some people reach 300 kg. It is natural, but it brings diabetes, cholesterol plaques, atherosclerosis, ischemic heart disease, and obesity with all its accompaniments.

Rule 4 — First examine, then devour, everything red and glossy, since it is either an insect or a fruit — both food. But red insects may be poisonous (ladybirds, some leaf beetles), red fruits may be edible or toxic. Hence the need to study first, which requires the neocortex — thinking, a different level altogether. From this grows exploratory behavior. Conveniently, some 40–45 million years ago primates developed the ability to see red: absent in prosimians, present in variable forms in monkeys, and fully realized in us. Meat, too, is red.

The Practical Conclusion

To avoid the modern consequences, one must think not only with the tuberal nuclei but also with the neocortex. The speaker offers his own experience: having been thin all his life and able to eat unlimited amounts, he began gradually gaining weight after age forty-something as metabolism slowed. His solution in the university canteen: look at everything he wants, then eat half as much as he wants. It works — though less and less over time, requiring ever more mental effort, plus movement and exercise, which help only modestly but are worth attempting.

The Limbic System: Smell, Emotion, and Memory

The diencephalon together with the archi- and paleo- structures of the telencephalon — archistriatum, paleostriatum, archicortex, paleocortex, plus the septum pellucidum and other elements — form the limbic system. This is not an anatomical unit but a sprawling functional system, ancient (arising in cyclostomes and the first fishes) and still fully operational, dedicated to three main things: smell, emotion, and memory.

• Its center is the hippocampus (the "seahorse"), part of the archicortex, tied together with other structures by the fornix.

How Chemoreception Becomes Emotional Memory

A vivid illustration: a small child walks across a summer meadow, is given an ice cream, smells the daisies, and feels wonderful — and the whole ensemble is associated together in the hippocampus. Forty years later the same adult walks across a similar meadow, smells the same daisies, and feels inexplicably good without knowing why.

Another child on the same day in the same meadow trips, falls face-first into the mud, drops the ice cream, and someone tramples it — perhaps the first child hit him as well. Forty years later, the same daisies produce sadness, equally inexplicable. The flowers are identical; the circumstances differed, and the number of such interacting influences across individuals is immense.

The Hippocampus and Memory Disorders

• The hippocampus holds short-term memory and therefore also acts as the recording device into long-term memory, which itself is stored in the neocortex, outside the limbic system. The hippocampus both writes to and reads from it.
• Damage produces striking effects:
  • Loss of short-term memory with long-term intact only up to the moment of injury — a "Groundhog Day" existence in which nothing new is ever retained, because the recording function is gone.
  • Loss of long-term memory while short-term still forms and may even be converted into new long-term memory — but nothing before the injury is remembered.
  • Complete loss of long-term memory leaving only short-term, so that a person remembers only the last five minutes of life.

The advice: look after your hippocampus.

Emotion as a Memory Technique

Because one of the brain's leading activities is communication and the recognition of other people, the best way to remember something is to endow it with emotion — to personify it.

For example, memorizing chemical elements: oxygen is harsh and rather angry; hydrogen is airy, light, and relaxed; iron is severe, heavy, and hard; uranium is radioactive and presumably malevolent; helium is cheerful and happy because balloons are filled with it. Labeling elements as evil, kind, cheerful, clever, or stupid harnesses the ancient emotional-memory machinery for abstract learning.

Personifying the World: Memory and Superstition

• Numbers work the same way as chemical elements: the digit two feels small, nasty, spiteful, and stupid; five feels round, plump, reddish, kind, and good. These associations are often school-derived, but holding them in mind — even unconsciously — improves recall.
• The reason is that the brain is built to remember interactions between people. When we endow something with the qualities of social communication, it sticks.
• The same mechanism produces superstition and religious belief: people spontaneously attribute consciousness, thought, and emotion to things that possess none of these.

The Limbic System on Autopilot

• The limbic system unites all of this and runs automatically, largely beyond conscious regulation.
• This explains highly emotional people who declare "I feel in my gut that this person is bad and that one is good." "Feeling it in the gut" essentially means detecting pheromones with the vomeronasal (Jacobson's) organ — a mechanism at roughly the level of the lancelet.
• At the lancelet level this was perfectly adequate: different pheromones meant a foreign population or a competitor; identical pheromones meant kin. At the human level, however, smells and pheromones no longer determine whether a person is good — that is determined by far more complex things, above all the neural networks of the neocortex.
• Practical advice: when you feel subconsciously that someone or something (even a car) is "good" or "bad," pause and ask whether the limbic system is signalling through chemoreceptors and other lancelet-grade machinery, or whether there is genuine reasoning behind it — because you also have a neocortex.

Delgado's Experiments: Aggression Can Be Switched On and Off

Since emotion is largely bound up with aggression, it can be regulated directly. The neurophysiologist José Delgado demonstrated this in a series of famous experiments:

1. The cat. An electrode implanted in the amygdaloid complex (part of the limbic system) made the cat fly into a rage. A signal sent instead to the head of the caudate nucleus calmed it completely — it became placid and purring.
2. The bull in the arena. A charging, furious bull was stopped mid-run by a remote-controlled signal to the head of the caudate nucleus; it turned away and calmly went to graze on the sand of the bullring.
3. The rhesus macaques. A cage contained a bad-tempered alpha male who, by definition, commanded everyone, baring his teeth and bullying the group. An electrode sat in his caudate nucleus, and the lever operating it was inside the cage. Being intelligent animals, the other monkeys quickly worked out that when he started throwing his weight around, they should run to the lever and pull it — whereupon he turned kind. (History does not record how long he remained alpha male afterwards.)
4. Human subjects. With an electrode in the amygdaloid complex, a patient reported: "Doctor, I feel I want to kill you right here and now with this chair — don't turn your back on me. I understand there is no reason for it and I shouldn't be angry with you, but I want to kill you. Just so you know."

The Ethical Verdict

• Delgado wrote a book (no Russian translation exists) whose title amounts to something like "How to Make Humanity Happy." Being an intelligent man, he concluded that the technical route is known — insert an electrode, attach a button, press it, and a person becomes kind — but that we should not do it yet, because we do not understand the brain well enough and sticking electrodes into people's heads is a dubious business. He abandoned such experiments himself; they now occur only when brain surgery is required for other reasons.
• The broader lesson: our brain does not differ greatly from that of a cat, a cow, or especially a macaque — mainly in size. The structures do exactly the same jobs. Simple, basic states can be regulated; higher functions are far harder.

Fear: Why We Are Built to Be Afraid

Fear is the reaction to something unexpected, incomprehensible, negative, and potentially dangerous. A great deal of brain tissue is dedicated to it: thalamic nuclei, the amygdaloid complex, the globus pallidus (the paleostriatum), and other deep central structures — the deepest, most archaic parts.

• Fear is useful. We must fear the unknown and unexpected precisely because we cannot calculate it quickly; when calculation fails, it is safer to be frightened in advance.
• For almost our entire history we were prey. Even once we became formidable hunters, there was always something that could kill us. Hence the triggers: unfamiliar people, darkness (we are diurnal animals), a glint in the dark that might be a leopard's eyes, sounds that are too quiet or too sharp, sudden movements — the same reflex as a cat startled by a cucumber. Something that was not there and suddenly is.

Fear, Surprise, and Laughter Are the Same Program

A remarkable insight: fright, astonishment, and laughter begin as strictly identical movements — the first fractions of a second of facial and vocal response are the same.

1. Something unexpected happens. By default it is presumed dangerous, so a fear reaction fires first.
2. To avoid the threat, one must frighten it away: the mouth opens and a loud shout begins — the initial "Ah!"
3. The brain then rapidly processes the situation, and one of three outcomes follows:
   • Genuinely frightening. The fangs are bared to intimidate, the lips lift vertically, and the sound becomes a continuous, sustained scream of horror.
   • Merely surprising. Eyes stay wide, the mouth stays open, but the fangs are not bared (there is nothing to intimidate), and the sound fades away — the vocalization of astonishment. Surprise is the intermediate state, when the brain has not yet fully worked things out.
   • Not dangerous after all. The brain concludes "I am not going to die right now" — which is wonderful — and laughter results. The mouth stretches sideways rather than opening vertically, teeth are essentially not bared (though humans, unlike chimpanzees, do expose them slightly), and the eyes narrow. Crucially, the program crashes: it had just been configured to scream continuously, so breathing becomes interrupted, producing "ha-ha-ha-ha."

Program failures happen. Sometimes the brain gets it backwards — an idiotic prank "goes wrong" and produces real terror instead of laughter; conversely, in a genuinely horrific situation a person may laugh hysterically. Onlookers say, "Why are you laughing, people are dying" — but he is not amused; his program has simply glitched.

The Fear of Strangers

One of the deepest fears operates at the highest level of the recognition system: fear of outsiders.

• Evidence: the Neanderthals of El Sidrón in Spain, about 50,000 years ago, were killed and eaten by other Neanderthals — they failed to spot the danger in time. Likewise the Sungir individual, who was first speared in the neck, then had his forehead cracked and his skull broken. He was buried beautifully, with beads — but he presumably did not enjoy the process.
• Consequently, as soon as a child becomes even minimally capable of recognizing individuals, it starts fearing strangers. A newborn does not distinguish faces and fears nothing, but that phase is brief. Once the brain can recognize parents visually, by sound, and by other cues, everyone unfamiliar is classified as dangerous. This is the correct reaction.

Modern Life and Manufactured Fear

• We now live in an extremely unnatural situation, surrounded by literally millions of unfamiliar people who are, in principle, mostly harmless. Many people become so relaxed that the fear system idles.
• But the amygdaloid complex, globus pallidus, and the rest must work. If there is objectively nothing to fear, the person goes looking for fear: horror videos, horror films, frightening sounds, haunted houses with things jumping out. Others chase sharper sensations — parachuting, rope jumping from bridges, motorcycle racing, rock climbing, caving — and sometimes get killed doing it, all for the adrenaline.
• The recommendation: keep it in check. One should fear, but in moderation — any extreme is unhelpful.

Dominance and Hierarchy

The Universal Mammalian Repertoire

As social interaction develops, simple rejection and fear reactions are replaced by social relations, group regulation, and hierarchical ladders. Strikingly, hierarchy and dominance in monkeys and in humans are strictly identical — indeed roughly the same across all mammals, from an opossum (not even especially social, yet it bares its teeth like the rest) to hedgehogs, dogs, and humans, who will bare their canines too if pushed far enough.

Dominance display in humans is pure mammalian behavior:

• Draw oneself up and inflate one's apparent size — humans can cheat with a mantle, a crown, or a beaver-fur hat.
• Wave the arms, beat on oneself or on tables.
• Endlessly bare the teeth. On simple, uncomplicated people — street toughs, for instance — this works flawlessly.
• A fixed stare from under frowning brows, with bared fangs — indistinguishable from a macaque.

Submission signals are equally identical: a glance upward from below, a lowered posture, a particular backward turn of the head. And downward gestures of condescension — a pat on the shoulder, the "dominant" handshake with the palm on top — work exactly as in primates.

The Human Speciality: Switching Dominance

Humans are the record-holders at changing who dominates.

The dog example. In the 1990s, the area around Moscow State University's biology faculty was chaotic — markets, warehouses, waste ground — and stray dogs roamed there. Zoologists from the Vertebrate Zoology Department studied them and found that when the pack needed to cross Lomonosovsky Prospekt at a light-controlled crossing, one particular dog knew how. Dogs cannot distinguish red from green, so this dog had to count the lamps, while also watching cars and people. At the moment of crossing, this clever dog commanded the whole pack and assumed the leader's role; it could even seize the formal leader by the scruff or snarl at him, and it had the right to do so with impunity. It might be a scruffy little dog — but at that moment it was in charge.

The human case. Films like Ivan Vasilievich Changes Profession illustrate the behavior brilliantly: at one moment Ivan Vasilievich brandishes a dagger and everyone crawls on all fours; at another he lowers his eyes, folds his hands, and looks aside, trying to frown but plainly submissive — while the policeman stares fixedly with wide eyes and bared teeth, suppressing him.

For normal people, dominance switches with the utmost ease. The speaker's own example: right now, even through a screen, he is in charge, directing attention to a slide and operating the projector. But if the person behind the camera says "stop, the lighting is wrong," he falls silent; if a fire alarm goes off, he meekly leaves the building; at the doctor's, he obediently lies on the couch, opens his mouth, breathes and stops breathing on command.

Why this matters organizationally. Because human activities are so numerous, dominance must rotate. When someone tries to subordinate everything to a single leadership — an absolute monarchy — the system coasts for a while on inertia and then falls apart, because no one can be a specialist in every form of activity. Genuinely strong leaders know how to hand off responsibility and the leading role:

• At a large enterprise, when the pipes leak, Vasya the plumber becomes the dominant and can tell the CEO where to go, because only he knows how to fit them properly.
• At another moment the general director commands; at a third, the chief accountant, who understands the paperwork; at a fourth, the lawyer, because the accountant has made a mess and the tax authority must be fended off.
• And at the entrance there is a security guard who says "no pass, no entry" — at that spot he is the highest authority. (Distortions do occur, especially with security guards.)
• In an ideal system, dominance is passed back and forth. The optimal version works reasonably well: president, prime minister, ministers, and so on down; or rector, dean, department head, senior researcher, junior researcher, senior lab assistant, junior lab assistant (the last of which, admittedly, no longer exists in nature).

Aggression Is Partly Written into Anatomy

• Aggression levels are inscribed to some extent in the size of the amygdaloid complex, the caudate nucleus, and the septum pellucidum.
• In some primates it is written into the skeleton itself: in baboons, either the males have huge faces with enormous, literally saber-like canines, or they are comparatively small with modest canines.

Baboons Can Be Made Kind

Robert Sapolsky's case is decisive. A troop of baboons lived near a hotel and were exceptionally vicious; the locals, exasperated, killed all the nastiest males. (The book's version differs slightly from Sapolsky's spoken account of what actually happened.)

• Only the conditionally "kind" baboons remained, and a novel behavior emerged: male-to-male grooming. Normally grooming runs male-to-female, female-to-male, or toward infants; a male grooming another male is unnatural for baboons — yet it arose here.
• Moreover, when males from neighboring troops joined (baboon males almost always transfer between groups), they adopted the new custom.
• The conclusion: even baboons can be made kind by the simple, unsophisticated method of killing all the vicious ones. This is not a recommended recipe for humans — but with baboons it works.
• The human analogue is justice: the police who protect us, courts, prisons, sentences. The system works, sometimes with breakdowns and blunders, but it is better to have it than not, because "anarchy is the mother of order" only in delirious slogans; in practice, living like baboons is best avoided.

Group Size: The Magic Number Thirty

For a collective to function as a unit, a certain number of individuals is required. Too few and the group is too simple and gravely endangered by predators and neighbors; a few more is better.

Remarkably, group size has barely changed since early australopithecine times. Looking across baboons, guenons, chimpanzees, gibbons, gorillas, and humans in all their variants, the numbers are astonishingly consistent: roughly 15 to about 50 individuals, averaging around 30–35 (Neanderthals averaged about 25).