The Scent of Eros 1995 revisited (Chapter 4)

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Evolutionists Cannot Account for the Origin of the Sense of Smell is one of the free book chapters from “The Miracles Of Smell And Taste”

When asked what Grok AI can compare to the “miracles,” it defaults to moronic claims that link the automagical emergence of energy from the cosmic void to the mathemagical evolution of people from pond scum.

See for comparison: A dataset of expression profile of certain microRNAs in Caenorhabditis elegans 7/4/25 and In-vitro transcriptomic profiling of indigenous Gaddi vis-à-vis exotic Labrador dogs: insights from systems biology 6/20/25

Taken together, they link light-activated miRNA abundance at the origin of life 6-10,000 years ago via God’s Creation of hydrogen in stars and protection from viruses via energy-dependent changes in angstroms to ecosystems and chromosomal rearrangements across kingdoms via the physiology of pheromone regulated reproduction.

For review, see: THE ANATOMY OF SMELLING

”Wen we smell another’s body, it is that body itself that we are breathing in through our mouth and nose, that we possess instantly, as it were in its most secret substance, its very nature. Once inhaled, the smell is the fusion of the other’s body and my own. But it is a disincarnate body, a vaporized body that remains whole and entire in itself while at the same time becoming a volatile spirit.” At least that is the way Jean Paul Sartresaw it in his 1963 biography of Baudelaire.

Scientists are much less poetic when they ask how we can inhale the essence of another’s body. How do we detect, sort out, identify, decode, and interpret the uncounted aromatic messages we suck into our nasal passages and then quickly expel?

Only seven of the 105 natural chemical elements-fluorine, chi rine, bromine, iodine, oxygen (ozone), phosphorus, and arsenic-have an odor. Odors are characteristic of organic molecules that contain car# bon atoms as a core with atoms of other elements attached  to that basic structure. In the case of a pheromone, the molecule might be a few carbon atoms linked together in a chain with other atoms attached as side branches.

The process of smelling starts with any molecule that is volatile, so tiny it is hardly affected by gravity’s pull. Such molecules can drift aimlessly in the ebb and flow of the winds. Every breath we draw pulls such particles through our nasal passages into our lungs where oxygen and carbon dioxide are exchanged. This express route runs from the nasal openings straight back a few inches to the opening of the throat at the back of the mouth and down to the lungs. While some eddies may reach the upper chamber of our nasal passages, this express route allows us to inhale and exhale quite efficiently twelve to fourteen times a minute.

Two branches of a trigeminal nerve reach from the brain to nerve endings widely distributed throughout the nasal cavities where they screen for dangerous or irritating odors passing through the express route. Chemical receptors associated with this nerve react to irritating odors with a prickly sensation  that causes us to sneeze. A whiff of ammonia will trigger this reflex, expelling harmful air before it damages the delicate tissues of our nose, throat, and lungs. After a reflex sneeze, fresh air rushes into the lungs, helping to revive a person in a faint.1

Above the nasal passage’s express route, in two narrow chambers just below the brain and behind the nasal bridge, are three ridges of spongy tissue that  warm and humidify incoming air. Faced with a potentially dangerous situation, with a fragrant rose or the buttery, gar, licky bouquet of shrimp scampi, we can sniff the air up into  these recesses. There the aromatic particles land on a pair of mucus,bathed patches of skin, smaller than a dime where ten million olfactory neurons wait with delicate branches floating in the mucus, waiting to be activated when their receptors find matching aromatic molecules brought in on the air we inhale.

The olfactory neurons have two main differences from the sensory neurons we use to see, hear, and feel. Neurons in the eye’s retina react to light only after it passes through the cornea, lens, and two masses of gelatinous material. The neurons in the ear’s spiral cochlea react to sound vibrations after they have hit the ear drum and been converted into mechanical vibrations by the bones of the middle ear. Touch neurons in the skin pass their messages through several connecting neurons to the spinal cord and up the cord to the brain. Chemical messengers, on the other hand, are “hot,wired”-picked up directly by receptors in the olfactory neurons and sent straight to the olfactory bulbs and processing centers in the brain.

The second unique trait of olfactory neurons is their ability to regenerate. Unlike neurons in our spinal cord, eyes, and ears, olfactory neurons constantly replace themselves, as a team of neuroscientists at Florida State University led by Pasquale Graziadei, Lloyd Beidler, and Michael Meredith, have documented over the past ten years.2

While Meredith has investigated neuml pathways in the olfactory systems of hamsters and sharks,3 Graziadei prefers studying the relation, ship  between  the  development of the  brain and nose in frog and chicken embryos. Constant  exposure to damaging, sometimes toxic molecules in the air, Gradziadei has discovered, kills most olfactory neu, rons in only four to eight weeks. Over the years, this devastation could wreak havoc with our interest in food and sex. Fortunately, our olfactory neurons can reproduce and replace themselves as they wear out.

This ability is an important factor in survival. A blind or deaf rat can still survive and mate to stay alive and keep the species going. A rat that cannot smell is much worse off. It cannot smell a poison in what looks and tastes like a great meal. It cannot discern the sexual readiness of a mate, or detect the scent of a cat waiting in ambush.

Beyond everyday survival and mating, the olfactory neurons play an early and major role in guiding the development of the fetal brain and setting up the production of hormones in the hypothalamus, pituitary gland, and ovaries and testes that are responsible for our sexual development and behavior in later life.

By the end of the fourth week of pregnancy, two thick plates of cells develop on the face of the fetus. Cells in these olfactory plates quickly migrate inward to become the olfactory bulbs and connect with the brain, particularly with the future hypothalamus and the limbic region. Some of these cells actually migrate into the future hypothalamus while others form a loose network scattered through the developing olfactory and limbic systems.These cells, known as GnRH neurons, quickly begin to produce GnRH, Gonadotropin,Releasing Hormone, the “starter hormone” that controls the cascade of hormones from the pituitary, adrenal glands, ovaries, and testes that influence all our sexual development and behavior.

Male fetuses end up with more GnRH,secreting neurons in their hypothalamus than do females. Down the line, this means males produce more luteinizing hormone (LH) and more testosterone than female fetuses. More testosterone causes male fetuses to develop male sexual anatomy externally-and internally, in the connections between nerve cells (synapses) in the brain.

Without the timely and proper migration of these GnRH neurons, many things can go wrong in fetal development. The sense of smell, for instance, can be impaired and, more crucially, the hypothalamus will not produce the GnRH  needed for normal sexual development and sexual behavior. Some brain development may even be affected.

In humans, Kallmann’s syndrome offers a good illustration of this effect. In boys and girls with Kallmann’s syndrome, the hypothalamus does not produce normal levels of GnRH. Without this hormone trigger, the pituitary cannot produce the hormones needed to tum on production  of androgens, estrogens, and progesterone in the  testes or ovaries. As a result, teenagers with this condition have a delayed puberty, often have trouble falling in love, and delay marriage. They may marry, but in an arranged sort of way without falling in love. Behind their impaired sexuality and lack of a sense of smell lies a failure of the GnRH neurons to migmte properly and trigger normal brain and sexual development.4

This connection between GnRH  neurons and brain development makes sense when we look at some experiments with tadpoles which are at the same stage of embryonic development as mammalian fetuses before they are born. When Gradziadei surgically removed the nose of a tadpole, it developed into a frog with no forebrain. Gradziadei suspects that  the GnRH  neurons in the olfactory system play a similar  major  role  in guiding development of the  human embryo’s brain.5  Some neuroscientists even maintain  that  our fore-brain and the  two hemispheres of our brain where we consciously process information from the outside world actually developed from the paired olfactory bulbs.

When  Graziadei removed the olfactory bulbs in the brain of a mouse, new neurons were produced to recreate the bulbs. Even when he removed 90 percent of the bulbs, the animal could still smell quite well, evidence that the olfactory bulbs are very good at compensating for injury and continued their essential function of passing on aromatic information to the brain from the outside world.

When Graziadei transplanted the very early embryonic structures of the olfactory system from one tadpole to another, his test animal not only developed two olfactory systems, but the stimulus produced a much larger than normal brain in the tadpole. When he removed the early nose and transplanted it to another part of the tadpole’s body, the brain developed but with striking abnormalities. Comparable tests transplanting the tadpole’s early eye structure showed few similar dramatic effects.6

Graziadei’s more recent work with chicken embryos takes us another step closer to understanding the importance of the olfactory system before and  after  birth. One  important link,  according  to Graziadei, is the fact that  “We see human babies born with anencephaly [with the brain’s twin hemispheres missing), and in every case, the babies also have no noses. Why is that? Obviously, there is a very fundamental, chemical connection here, and we want to find out not only what it is, but how it works.”7

A BRIDGE TO INNER SPACE

In the main olfactory system with which we are most familiar, aromatic molecules are caught in the moist mucus on the ridges of the upper nasal passages. Each of the millions of odor-sensitive cells in these ridges has a tassel of six to twelve hair like cilia floating in the mucus.8

Scattered in the surface of these microscopic cilia are pockets formed by chemical receptors, similar to those that  bacteria and one celled animals use to detect food and toxins. When an aromatic molecule encounters a receptor pocket that fits its molecular shape, the two join up, like a key slipping into a lock.9

The union of an aromatic molecule with its proper receptor triggers a minute change in the electrical balance of the cell membrane that “fires off’ an electrical message through the long branch or axon leading to the olfactory bulbs in the base of the brain a few millimeters above the passages.10

That  electrical  message originates in the base of the receptor pocket where some fifty G protein molecules are attached. When the right odor comes along and fits into its receptor pocket, the receptor twists just enough to release these proteins into the cell material inside the thread like cilium. When the freed G proteins interact with other proteins inside the cilium, they open up channels in the membrane of the receptor neuron. This allows sodium ions-sodium atoms with a positive electrical charge-to pour into the body of the neuron. When the positive charge builds up to a critical level, the neuron “fires” an electrical pulse along its long thread like axon to the olfactory lobes in a process that takes only a few thousandths of a second.11

In addition to being able to discriminate between the molecules that can activate its receptors, the olfactory neurons must have a mechanism that modulates the intensity of each response.The size and duration of an impulse is fixed, but its frequency varies. Decoding the neuron’s response means decoding the frequency of the nerve impulse.

Linda  Buck,  a Harvard University neurobiologist, has  added another  piece to our understanding of how we smell when she identified the genes responsible for as many as a thousand different receptors in the mammalian  nose. Even though some of these genes may act in concert  to produce the thousand receptors, it may be that close to one percent  of our hundred  thousand or so genes are devoted  to creating our odor-sensitive receptors. Only  three  of these  hundred  thousand genes are responsible for producing the receptors for the three primary colors entering  our eyes as light. And  that  says something  about  the relative importance of the two senses of smelling and seeing. 12

Author’s comment: Linda Buck shared the 2004 Nobel Prize in Medicine with Richard Axel “for their discoveries of odorant receptors and the organization of the olfactory system. In a series of pioneering studies the laureates have clarified in molecular detail how our sense of smell works.

Although we may have only a thousand different odor detecting neurons in our main olfactory system, some humans can recognize ten thousand distinct odors. How can the brain distinguish so many odors with only a thousand receptors? Buck suggests that while each neuron may carry only one kind of receptor and send only one message to the olfactory lobes and brain, the brain can distinguish between different odors if they trigger more than one receptor and different combinations of receptors. In other words, if we are dealing with four different receptors–label them A, B, C, and D for convenience– a lemon molecule may bind with the A, B, and D receptors to send a triple message to the brain decoding circuit. An orange molecule may activate the A, C, and D receptors, a tangerine odor the A, B, and C receptors, and a grape fruit the B and C from this set plus another  receptor, say a G receptor. Combination messages from the  thousand  different  receptors  could account for our brain’s ability to identify ten thousand odors.13

This model makes sense for complex odors especially when, in our example, some of the receptors activated  by orange, lemon, tangerine, and grapefruit odors are the same for all citrus scents. Buck admits that a neuron may carry more than one kind of receptor, and that  the coding scheme may be more complex than the model she has suggested.

Once triggered by the appropriate aromatic molecule, an olfactory neuron  sends an impulse along its axon branch  through  a thin  bony layer directly into the paired olfactory bulbs just above the nose in the floor of the  brain. These  extensions  of the  brain contain bundles of neurons,  each  capable of processing impulses from about  twenty six thousand  receptors. These bundles filter out the trivial static and send essential signals along to other regions of the brain.

Like other  biological  processes, the  olfactory system includes  a thermostatic  feedback loop that keeps the system from running amuck if we get carried away with a particular aromatic stimulus. When  mes, sages from your stomach tell your brain it is full, this message is passed along to the olfactory bulb, toning down the impact of that second fragrant piece of homemade, fresh-from-the-oven apple  pie  nestled against all-natural vanilla ice cream.

There are also times when a particularly strong, noxious odor is unbearable. In short order after being assaulted with the overwhelming stench  of a slaughter house or cesspool, the brain reacts by refusing to process any more messages of that  particular odor. Nasal fatigue provides an important defense mechanism against sensory overload.

Hidden behind these obvious reactions to various odors is a much more subtle and powerful double reaction. Our olfactory system uses G-protein activity in the olfactory receptors to convert odors and pheromones into electrical signals. These signals are converted into a chemical signal, GnRH, which acts as both a neurotransmitter and a hormone. As a neurotransmitter, GnRH may directly influence our behavior.14; As a hormone produced in the hypothalamus, GnRH regulates hormone production in the pituitary gland.15 Because hormones from the pituitary flow through the blood to every organ and system in the body, smell plays a major role in regulating  all kinds of functions  essential for life, from growth, body metabolism, maintaining proper fluid balances, insulin production, stress management, sexual development, mating, milk production and breast feeding, to fighting, fleeing, feeding, and more.16 All this means that odors and pheromones processed by our main olfactory system clearly affect and influence our sexual development and behavior.

Messages from the olfactory bulbs are also sent along to the olfac, tory cortex in the brain which helps distinguish odors based on past experiences. This enables us to tell the smell of burning leaves from the quite different smell of a burning cloth pot,holder. Messages also travel from the olfactory bulbs to the memory and emotional  centers of the brain, and to the thalamus which appears to connect  limbic odor mes, sages with higher thought  functions in the thinking  part of the brain. The conscious brain caps this process by relating odor messages to mes, sages and memories from the other senses.

SNAKES AND Tim VNO

So far, in talking about how we smell, we have concentrated on the main olfactory system, located in the nasal passages and main olfactory bulbs. But some animals also have an accessory olfactory system (AOS), which is specialized for detecting the subliminal signals of pheromones. Scientists have known about this AOS in reptiles and mammals since the early 1800s, but only recently have they begun to look for it in humans.

Research on how we see and hear has always taken precedence over research on how we smell, but the fact that in other animals the AOS processes pheromones which operate below the conscious level and affect the emotions and sexual behavior may in part explain the reluctance  of researchers to probe into this aspect of how humans smell. If we were to get philosophical about the lack of research on pheromones and the AOS, we might suggest that researchers and the public have been turned off by the possibility humans might rely on an olfactory system that is dominant in the life of snakes and reptiles. In addition, the ancient Hebrews viewed the serpent as the disrupter of the peace in the mythic Garden of Eden when it allegedly seduced the first couple. In many cultures, but especially in the West, snakes trigger fear and revulsion. That forked tongue continuously flicking in the air seems somehow threatening and satanic.

In reality snakes, like other reptiles and mammals, test the air for aromatic clues to danger and food.17 As the tongue darts back and forth between the air and the snake’s mouth, it captures heavy aromatic chemicals and dumps these into a pair of odor-sensing sacs, the vomero, nasal organs (VNO), which sit in the roof of the mouth beneath the main olfactory system. The snake’s forked tongue and paired VNO allow it to take two slightly different scent samples and send a stereo-scopic message to the brain. By comparing the strength  of the two scents, the snake knows the potential mate or meal is straight ahead, or more or less to the right or left, much the way we tell the direction of a sound by messages from our two ears.18

Early in the history of the vertebrates,  reptiles developed  the VNO/AOS to handle odor messages that are too heavy to be sniffed, even though their messages may be vital to an animal’s survival. In the VNO sacs, a sensory epithelium similar to that of the main olfactory system begins decoding the pheromone messages and converting this information into electrical impulses.

In other animals, pheromone messages from the sensory neurons of the VNO feed through a maze of neurons directly to a tiny organ called the accessory olfactory bulb (AOB) buried just below the frontal lobes of the brain. Electrochemical signals to other neurons increase production of GnRH that enhances the olfactory responses and speeds up neural transmission with or without altering other hormone levels. After some additional decoding in the AOB, nerve impulses go directly to the amygdala, an area in the limbic system concerned with a variety of behavioral mechanisms and emotional responses.19 From the amygdala, the signals are fed to the GnRH-producing circuits of the hypothalamus that regulate sex hormone production, sexual differentiation, and sexual behavior. This includes control of the body’s basic Four Fs-feeding, fighting, fleeing, and mating.20

The VNO is essential to reproduction in other animals. Without its response to pheromones, production of key sex hormones would be disrupted.21 Without trigger signals from the VNO the hypothalamus would not start, stop, or cycle the levels of its production of GnRH that regulates production of several hormones in the pituitary master gland.22

It also facilitates mating behavior, especially in males with low testosterone or impaired sensations from their genitals and in females whose hypothalamus is not up to par in triggering the cycle of sex hormones.

Blocking input to the VNO of a male garter snake will completely eliminate any sexual behavior. Blocking its main olfactory system has no effect on mating.23 Male snakes respond to sex pheromones secreted onto the skin as a prelude to courtship. During courtship, the male snake increases its tongue-flicking as it rubs its chin up and down the female’s back in a sort of full body massage. However, some male snakes, known as “she-males,” produce sex pheromones that  make them smell like females to other males. This trick misleads competing males into trying to mate with them. While the confused male tries to court the “she-male,” the “she-male” wastes no time and immediately mates with the available true females.24

Both the snake darting its tongue and the bull licking the vulva of an estrous cow are picking up pheromones that are pumped into the VNO. In both cases, with variations allowing for the differences between snakes and cattle, this sets up a chain reaction from the VNO to the olfactory bulbs and hypothalamus, which then controls sexual development and behavior.25

The  way the AOS is put together varies quite a bit from one species to the next. Researchers have found the VNO sacs in humans, tucked inside the bony area, near where the hard palate and nasal sep tum meet behind the nostrils. But they have not been able to find other components of the mammalian or reptilian accessory olfactory systems in humans. Nor have they been able to trace the neural tracts that logically must exist to connect the human VNO with some region of the limbic brain.26

Embryologists have long admitted that  the VNO does develop early in human fetal life, but they claimed it degenerates and disappears long before birth.27 If traces of the VNO remained after birth, it would be obvious that they could not function in the noble, rational human. How could we admit that something so primitive, instinctive, or reflex ive as the VNO and pheromones could play a part in human mating?28

This picture changed unexpectedly and dramatically in 1991, at an international symposium on advances in mammalian pheromone research held in Paris under the sponsorship of EROX Corporation, an American company  pioneering research  on human  pheromones. David Moran and colleagues reported they found vomeronasal pits in nearly every one of two hundred  persons they examined.29 Their examination of these VNO structures with light and electron micro scopes provided new details on the cells in the human VNO that are “unlike any other  in the human body.” Another  report by Garcia Velasco and Mondragon found vomeronasal structures in nearly every one of the one thousand subjects they examined.30 Stensaas and colleagues confirmed the presence of two kinds of “potential receptor elements” in the human VN0.31

Suddenly, what scientists had believed did not exist in humans did in fact exist. Suddenly, the VNO emerged as an important part of the human sensory system. Equally important, the newly discovered human VNO appears to function much the same way as it does in other ani mals.32 Researchers began to suspect and explore links between the human VNO, pheromones, and human behavior, learning, memory, and emotions. Once again, scientists have found another of Ariadne’s threads linking humans with our animal ancestors.

Meanwhile, neuroscientists have  proposed  more than  sixty hypotheses, models, and theories to explain how nerve cells detect and sort out odors in animals and humans. The model described earlier in this chapter is the latest description of the anatomy of smell, but it certainly will be challenged and refined as the research continues.

While the mystery of how the brain works to control behavior is the supreme question confronting all neuroscience, Meredith, a co-director  of the  Florida State  University  Program in Neuroscience, believes the answer may first come from those who are tracking how the brain receives, interprets, and identifies the constant  barrage of messages that come to our brains through our noses from the outside world. Recent research into how we smell is bringing us tantalizingly closer to some real answers. Before long, this mystery may be solved.

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