The Ecology of Humans – Touch


To enjoy life, we must touch much of it lightly. ~ French writer Voltaire

Touch is the longest single entry in unabridged dictionaries of many languages. The associations are incredibly rich, if a bit touchy. Feeling comes from being touched emotionally. Stay in touch.

Of all the senses, touch produces the most intense memories. Touch makes the world seem real like no other sense.

Humans can compensate, at least somewhat, for loss of vision, hearing, or smell/taste. But blocking tactile sensation produces a profound, unshakable disorientation that quickly leads to psychosis. Touch defines our sense of reality.

Learning through touch is instinctual; as important as vision for retaining information. Even newborns can recognize objects by touch alone. ~ American cognitive scientists Derek Cabrera & Laura Colosi


Years wrinkle the skin, but to give up enthusiasm wrinkles the soul. ~ American general Douglas MacArthur

Every living entity, from a cell to the walking colony known as a human, has a physical barrier of delineation. Cell have membranes. Plants and animals have functionally differentiated organs that act as boundaries between the inner and outer world. The human body is largely surrounded by skin.

Skin is one the largest single human organs. Skin covers 5.5 m2 for an average adult male and weighs 3.6 kg: 6–8% of total body weight. A piece of skin the size of a US quarter has 3 million cells, 100 sweat glands, 50 nerve endings, 1 meter of blood vessels, and nearly as many lymph vessels.

The entire skin of a body has 640,000 sensory receptors connected to over 1/2 million nerve fibers. Each fingertip has over 3,000 touch receptors. Sense receptor spacing varies from 7 to 135 tactile points per cm2.

There are distinct task-specialized touch receptors which may work in complementary fashion. Their relative densities vary depending upon an area’s tactile employment.

Meissner’s corpuscles are mechanoreceptors sensitive to light touch. They detect if an object is slipping from your grasp.

Merkel cells detect prolonged pressure. Besides appreciating texture, Merkel cells convey information about an object’s weight and how tightly you are gripping it.

So, Meissner’s corpuscles and Merkel cells work together to let you hold eggs without crushing or dropping them.

Human genitals, which work part-time as pleasure centers, are rich in Meissner’s corpuscles. So too nipples. But few Merkel cells are employed there – which is why you cannot read braille with your penis, clitoris, or breasts.

Melanocyte skin cells sense ultraviolet light using a photosensitive receptor – rhodopsin – also found in the eye. As a protective measure, UV light triggers melanogenesis within hours. Melanogenesis is the production of melanin. Melanin is a pigment, ubiquitous in nature, that acts as a photoprotectant. Melanin absorbs 99.9% of UV radiation, transforming it into harmless heat, which is why sun-exposed skin is excessively warm.

Hair follicle density goes from zero on the lips to 150,000 per cm2 on the scalp.

Skin in thinnest – 1/10th millimeter – on the eyelids, lower abdomen, and external genitalia, and thickest on the palms of the hands and soles of the feet: 3–4 mm.

Skin orchestrates an array of functions:

1) waterproofing and puncture-resistant protection;

2) guarding against foreign invasion as part of the immune system;

3) temperature regulation: skin capillaries constrict to drive blood into the interior, conserving body heat, or enlarge to radiate heat from the interior; sweat also acts to cool via evaporation;

4) a metabolic organ, with metabolism, storage, and catabolism of fat, along with storing and adjusting water and salt levels;

5) a source of moisture and lubrication to other organs;

6) vitamin D synthesis;

7) excretion via the sweat glands;

8) passer of gas, both in and out;

9) blood pressure regulator: in a biological butterfly effect, the opening and closing of capillaries can assist in making large shifts in blood flow;

10) a sensory organ, especially on the primary sources of contact with the external world: the palms and soles.

Skin is both protection and portal: blocking toxins and preventing excessive fluid loss but allowing organic nutrients in as well as expelling waste.

The skin is the body’s most adaptable tissue. From the velvet of a baby bottom to the parchment of a geezer’s forearm, skin tells a health story in thickness, color, shape, and function. Skin responds to the demand made upon it: becoming thin and sensitive or calloused and unfeeling.

Human skin owes its toughness and adaptability to being arranged in layers. The outermost covering, the epidermis, has 4 layers.

The epidermis is continually being shed and replaced. An epidermal lifecycle is ~27 days. The epidermal layers have no blood vessels. They receive their irrigation and nourishment from the underlying dermis.

The dermis is thicker than the other layers, housing all the blood and lymph vessels that service the epidermis; hair follicles, along with their sebaceous glands and erector muscles; sweat glands; and most of the skin’s nerve endings.

The dermis is heavily laced with connective tissue, giving skin both its tensile strength and its pliability and elasticity. The connective tissue is woven into the subcutaneous connective tissue which further adheres to deeper layers. The dermal connective tissues also house the main healing mechanisms for the skin.

The connective dermal web provides the changes in appearance of aging skin. Aging leads to moisture loss, a dynamic where the fullness of skin is literally drained away, leaving it drier, thinner, and wrinkled.

Aged skin is less elastic. Dermal aging shows a person’s biological age as opposed to chronological age. Heredity, diet, disease, trauma, and stress all make statements on the skin.


Beauty is only skin deep, but ugly goes clean to the bone. ~ American poet Dorothy Parker

The anaerobic soil bacterium Clostridium botulinum secrets a toxic protein – botulin – during sporulation, as protection for the spores. Botulinum toxin (botox) is the most powerful neurotoxin known, causing muscular paralysis and disrupting the autonomic nervous system in a wide range of animals, including fish, birds, and mammals.

Botulism is the paralytic illness caused by botox, brought on by ingestion or wound contamination. Infants are particularly susceptible to botox poisoning by eating contaminated food. Honey is a known risk factor, particularly for babies in the their 1st year, accounting for 20% of infant botulism cases.

All forms of botulism lead to paralysis that typically starts with facial muscles and spreads to the limbs. Severe cases paralyze the breath muscles, resulting in respiratory failure.

In 2002, the FDA gave regulatory approval for botox injections to temporarily improve the appearance of moderate-to-severe frown lines between the eyebrows. There seems to be no wrinkle in governmental approval for medical self-abuse that is less than lethal and not mind-altering.

Botox injections, which temporarily mask facial wrinkles by inflammation and localized muscle paralysis, has become popular with vain women and men worldwide. Of those there is no shortage.

Botox injections account for half of the 11 million US cosmetic procedures, earning $2.7 billion in 2016. The American cosmetic surgery market altogether raked in more than $16 billion in 2016.

The risk and dangers of botox are well publicized. This anti-aging inanity is being successfully marketed to youngsters.

The effects of a botox injection may last up to 8 months; its effects are cumulative for repeated applications. Ironically, actors and actresses, who rely upon expressive facial muscles to show their skills, are high-profile users of botox “treatments,” desperately striving for that youthful look while decimating the capability of conveying their craft.

Skin and Mind-Brain

We do not experience our body as a set of fragmented parts, but rather as a single entity. ~ Swedish neurobiologist Valeria Petkova

The skin acts as the spatial map of the self, instrumental in proprioception: the physical sense of self. The mind-brain delineates self via nerves, mapping body parts from the skin, muscles, and bones, which are also nerve rich. This sensory homunculus is how the mind-brain separates functionality and pinpoints bodily locations.

Phantom limb syndrome, where a person continues to feel that a missing limb is still there, exemplifies this mental mapping. Phantom limb syndrome is something of a misnomer, as the sensations also occur with various body parts, including breasts, eyes, teeth, and even internal organs.

The skin acts as a revealing surface of the mind at times. There are several skin responses, such as blushing, paling, goose bumps, sweating, chills, and clamminess, that reflect mental states.

The skin is an advertisement of health throughout the body. Healthy circulation renders a pink, warm complexion. An unhappy liver yellows the skin and makes it clammy. Faulty diet paints the skin as oily or dry. Chronic anxiety and exhaustion darken the skin under the eyes. Pimples, boils, cysts, and rashes indicate chronic mental anguish and/or physical disorder.

Our intelligence is a distributed, integrated system, with the mind-brain being headquarters, but with innumerable branch offices. Glia cells are distributed throughout the body and perform localized processing. This includes skin responses.

The Sense of Touch

Not only our geometry and our physics, but our whole conception of what exists outside us, is based upon the sense of touch. ~ English philosopher Bertrand Russell

Touch is the mother of senses. Ancient amoebas had a well-developed sense of touch. From womb to tomb, the sense of touch is the interface to the world, a constant flow in enormous variety of sensation.

Touch is the first sense to mature as an embryo. It is the sense of touch that convinces us that we live in a physical world.

Generally, women have a more delicate sense of touch than men, owing to smaller fingers. The more petite digits have more closely spaced sensory receptors.

Tactile acuity affords superior dexterity and explains why the superiority of so many crafts reliant upon manual dexterity come from women’s hands. As the senses go a long way in defining worldview, an enhanced sense of touch also partly explains why women typically have finer social sensitivity.


The ability to sense humidity and wetness is an important attribute in the animal kingdom. For many insects, discriminating between dryness and wetness is vital for procreation and survival. Sensing wetness is also critical for humans, for both behavioral and autonomic adaptations. ~ English physiologist Davide Filingeri et al

There are no specific skin receptors for sensing moisture. Yet there is a distinct feeling we get when touching something wet.

Wetness is a perceptual illusion: a mental construction through intricate multisensory integration. We learn to perceive wetness through experience.

The human sense of humidity is temperature dependent. Whereas warm wetness is a modest sensation, moisture is keenly felt in the cold. This difference is an evolutionary outcome. Being soaked in warmth can be soothing. In contrast, getting soggy when cold rapidly robs the body of heat, and so represents an environmental hazard.


The other senses are exquisite sensitizations to touch: compressions of air on the ear drum; vibrant chemicals on the nasal membranes and taste buds; energetic photons hitting the retina.

Reflecting skin’s protective role, pain receptors outnumber all others. Pressure sensors come in second; different ones detect light or heavy, pressure transitory or constant. Then cold receptors, and finally, the sense of warmth.

Heat and cold have specific nerve receptors. Other nerve endings may pick up on several or a wide variety of stimuli. 8 different tactile nerve endings are known, but that’s an undercount. Nerve receptors are packed so closely to make unraveling exceedingly difficult.

One sensor found everywhere on the skin are free nerve endings. Free nerve endings can sense light touch, pressure, and pain, as well as reacting to specific chemicals spilled from damaged cells.

Touch sensors (mechanoreceptors) are most concentrated on the lips (hence the pleasure of kissing, especially lightly); and most sparsely on the back (hence the pleasure of back rubs).

The acutely sensitive tactile corpuscle, located just below the epidermis, is most abundant on the lips and fingertips. This ending is particularly sensitive to a moving light touch, but quickly adapts (ceases to register) to constant contact.

Expanded tip tactile receptors are like tactile corpuscles except that they continue to respond to long-continuing contact, affording the ability to pinpoint an object in stationary touch.

The human skin is covered with hairs that act as a proximate sense of touch, and as a defense: one readily notices a small insect crawling on the skin because of hairs being disturbed, not the skin per se being touched.

Every hair on the body has a follicle wrapping: a hair end organ, which registers the slightest movement of each hair. There are distinct hair types, each with specific sets of sensory receptors.

The network of receptors distributed throughout the skin lets us construct a model of the proximate world. These receptors also connect to emotion processing, and so help suss and convey social intentions. A gentle touch speaks volumes.

Bulbous corpuscles – pressure sensors located deep in the skin – are touched by massage. They do not rapidly adapt, and therefore sense continued pressure on deep tissues. Bulbous corpuscles are particularly abundant at joints, thus informing about the location and movement of limbs.

Pacinian corpuscles are in the skin and deeper tissues, but unlike bulbous corpuscles, Pacinian corpuscles adapt within a tiny fraction of a second, and so detect tics, fleeting pressures and distortions, and vibrations.

Although the density distributions vary from one body area to another, no substantial patch of skin lacks nerve endings. Interpenetration is so thorough that single tactile stimulation almost never occurs. The sense of touch is an interdependent dynamic, informing about forms and textures without and within.

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Touch is central in building the foundations of social interaction, attachment, and cognition. ~ German psychologist Antje Gentsch et al

Tactile pleasure and pain are gradients that commonly mix in the mind. The nature of touch, its intensity and repetition, as well as control over the source, shape the interpretation of touch.

Affectionately touching the skin of someone else gives an illusory impression of soft skin. The mind has the skin of a loved one feel silkier than it really is.

Physical contact is essential to health: a form of psychological nutrition. Sensory malnutrition at any age can be debilitating, but especially, like other deficiencies, is more alarmingly harming to the young.

Biochemists point to elevated oxytocin levels to quantify the effect of nutritional touch, but that is like pointing to elevated glucose levels to quantify dietary nutrition: the measure is an inadequate statement of holistic effect.

Trust and touch are often intertwined, as touch can be both a physical and emotive experience. While everyone enjoy socially-affirming touch, women are more susceptible to tactile manipulation than men.

Caressing can also be a vicarious pleasure. As a physical facet of empathy, the mind naturally reacts strongly to the sight of pleasurable contact between others – hence the popularity of romantic movies and pornography.

Babies are learning a great deal about touch in the uterus. They suck on their thumbs, grab the umbilical cord, and are constantly bumping against the walls of the mother’s abdomen. ~ American touch researcher Tiffany Field

A human embryo develops a sense of touch in its 6th week, when it is less than 2 cm long. Beginning in the womb, touch guides development of brain regions related to social behaviors.

Touch is central to the way that babies interact. ~ American neurobiologist Carissa Cascio

Tactile stimulation is essential to infant survival. Studies from the early 20th century reported infant mortality reaching 99% within a year of admission into orphanages where caretakers gave no care. Those that survived were forever marred by stunted growth and mental retardations.

The same happens to young abandoned animals put into shelters or zoos where the time is not taken to act humanly to the inmates. Animals who receive early affectionate contact develop superior functionalities and immunological resistances.

The effects are strengthened if fondled throughout maturation. Licking is a common form of affectionate contact for many animals, the equivalent to human kissing.

Mental disorders of all sorts are worsened by lack of positive physical contact with others. Violence, rage, and other emotional disturbances are related to tactile deprivation.

 New Guinea Tribes

American cultural anthropologist Margaret Mead observed various tribes in New Guinea. Two in particular – the Arapesh and the Mundagamors – were studies in extreme contrast.

The Arapesh delighted in their children, fondling them regularly. An infant was rarely out of someone’s arms. Mothers carried their infants in slings within them throughout the day. A child nurses 3 to 4 years. Mealtime was a happy time for both mother and baby, with much affection. Other adults reveled with affection to children. The Arapesh were pacifists: easy, gentle, peaceful; a society in which competitive or aggressive games were unknown. Exploitative warfare was absent.

In contrast, Mundagamors treated children as a labor. Often, before a child was born, there was discussion about whether to let it live. If the infant survived birth, it was carried in a rough basket on its mother’s back. The basket was hung on a wall while she was working. Infants were suckled only when their crying could not otherwise be stopped. As soon as suckling stops, back into the basket. An infant had to practically fight for food, clamping a mother’s breast aggressively, frequently choking, and infuriating a mother. The Mundagamors’ nursing experience was, Mead wrote, “one of anger and frustration, struggle and hostility, rather than one of affection, reassurances, and contentment.” As soon as a child could walk, weaning abruptly ended, even slapping a child when it approached the breast. Mead reported that the Mundagamors were “an aggressive, hostile people who live among themselves in a state of mutual distrust and uncomfortableness.” Both men and women were warlike in temperament, seeking power and position. The Mundagamors were cannibals.

Sensing Self

Touch is a dialectic: touching the world defines the self. In touching something, 2 things are affected: the object touched and the person touching. Touch is an interplay between the object of experience and the sensation of the experience.

Pleasure and pain are interpretations of touch. Those interpretations define what is touched and how.

Associations define the self. Associations are by definition what is touched and held and what is not.

At the most intimate level, a human conveys to another person meaning via touch. In those moments the nature of self is revealed.

The touch of desirous love is the epitome of emotive tactile sensation, for both giver and receiver; though sometimes, love is expressed in what is not touched.