Human Pheromones: An Accurate Conceptualization
This link; another link to The Scent of Eros: Mysteries of Odor in Human Sexuality; and the excerpts below, provide a concise summary of essential points, statements, and facts to be found in the book I co-authored with Robert T. Francoeur. The précis was published in the online journal “Psycoloquy” on October 29, 1995. It represents what may be the first permanently available on-line indicator of my interest in human pheromones and also indicates my first attempt to teach others about the significance of odor in the development of human behavior. In 1996, I co-authored From fertilization to adult sexual behavior, which further extended the concept of human pheromones.
In 2001, I co-authored Human pheromones: integrating neuroendocrinology and ethology, which referenced the detailed reciprocity in olfactory-genetic-neuronal-hormonal-behavioral relationships that appear to link the nature and nurture of human sexuality and the influence of sensory stimuli, especially chemosensory stimuli, on human sexuality. In 2001, a ground-breaking report by the National Academies of Science’s Institute of Medicine concluded that the study of sex differences could lead to significant improvements in health for both women and men (Wizemann & Pardue, 2001). The report recommended that research on sex differences be conducted at every level—gene, cell, tissue, organ, and organism—and that sex differences be studied at every stage of life, from conception through death (Marts & Resnick, 2007). As indicated in Sex Differences and the FDA Critical Path Initiative one of the most extraordinary changes over the last few years is the ability to globally analyze biological systems, and to use this global analysis in the development of therapeutic agents designed with full considerations for sex differences in their effects, and their side-effects. In 2007, I published The Mind’s Eyes: Human pheromones, neuroscience, and male sexual preferences as a book chapter in the Handbook of the Evolution of Human Sexuality after its 2006 publication in the Journal of Psychology & Human Sexuality. In 2012, I expect to publish an article in Socioaffective Neuroscience & Psychology that links human pheromones and food odors to their epigenetic influences on the socioaffective nature of evolved behaviors via the same gene, cell, tissue, organ, organ system pathway I first detailed in The Scent of Eros: Mysteries of Odor in Human Sexuality. The recurring theme of this pathway, which links the social environment to the development of behavior in every species, is as important today as it was when I first began my research. I am attempting to make this perfectly clear.
This Precis provides an overview of the book “The Scent of Eros: Mysteries of Odor in Human Sexuality,” which details for a general audience a five-step biological pathway that allows the social environment to influence the genetic nature of mammalian behavior. This pathway is: gene-cell-tissue-organ-organ system. Moreover, though there are many environmental influences on genes, mammalian pheromones are the only known social-environmental stimuli that appear to activate gene expression in neurosecretory cells of tissue in the brain, an organ that is essential to any organ system involved in behavior. Human pheromones appear both to elicit a homologous “neuroendocrine” response and to influence behavior. Thus, human pheromones may fulfill the biological criteria required to link at least one aspect of a sensory-based, nurturing, social environment: olfaction, to the genetic nature of human behavior through a five-step pathway common to all terrestrial mammals and to many other vertebrates.
AUTHOR’S RATIONALE FOR SOLICITING COMMENTARY
As evidenced by menstrual synchrony and suppression, coitus-induced
ovulation, entrainment of hormone cycles in couples, and by other
effects, human pheromones elicit a homologous “neuroendocrine” response
and also appear to influence behavior. Thus, human pheromones may
fulfill the biological criteria required for linking at least one
aspect of a sensory-based, nurturing social environment to the
genetic nature of human behavior through a five-step pathway common to
all terrestrial mammals and to many other vertebrates.
The concurrent development and maturation of the olfactory,
GnRH neuronal, neuroendocrine, reproductive sexual, and central nervous
systems allows postnatal pheromone exposure to have organizational and
activational effects on the brain and on behavior, whenever in life
this exposure occurs.
The influence of human odors and human olfaction in behavioral and
brain sciences is an issue that has generally been avoided despite the
existence of mammalian and other phylogenetically sound models;
information in this book contradicts the current theory that humans are
microsmatic and that we do not use olfaction to the same degree as
other mammals, albeit subconsciously. The book integrates a body of
brain and behavioral data (e.g., olfaction in classically-conditioned
hypothalamic-pituitary-gonadal axis driven behaviors); and places
dissociated areas of research into an evolutionary perspective.
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psycoloquy.95.6.33.sex-odor.1.kohl Sunday 29 October 1995
ISSN 1055-0143 (22 paragraphs, 2 references, 266 lines)
PSYCOLOQUY is sponsored by the American Psychological Association (APA)
Copyright 1995 James Kohl
Precis of:
THE SCENT OF EROS: MYSTERIES OF ODOR IN HUMAN SEXUALITY
by James Vaughn Kohl and Robert T. Francoeur
New York: Continuum Publishing Company, 1995
14 chapters, 268 pages
KEYWORDS: behavioral development, genetics, gonadotropin, human
sexuality, neuroanatomy, neuroendocrinology, odors, olfaction,
pheromones, releasing hormone
1. This book incorporates both non-human animal and human models of
reciprocity among odors, olfaction, neuroendocrinology, and behavior.
It details the likely influences both of human chemical communication
and of olfaction on genes in neurosecretory neurons. These neurons are
found in brain tissue responsible for integrating, coordinating, and
directing reproductive endocrine function in organs that comprise the
organ systems known to influence mammalian reproductive sexual behavior
and human sexuality. Though this book is not written to meet any
requirements of a “hard scientific” approach to interdisciplinary
topics, it is fully referenced for the knowledgeable scientist and for
those interested either in further study or in support for any
conclusions. Also included are chapter notes, a glossary, and an
index.
2. After a Foreward by William E. Hartman and Marilyn A. Fithian and an
Introduction by the co-author, Chapter 1 begins with commentary on
previously published works by various scientific authorities who have
offered their insights into the importance of human chemical
communication. Among these authorities are Havelock Ellis, Irving
Bieber, and Lewis Thomas, who offered the following statement: “I
should think we might fairly gauge the future of biological science,
centuries ahead, by estimating the time it will take to reach a
complete, comprehensive understanding of odor. It may not seem a
profound enough problem to dominate all the life sciences, but it
contains, piece by piece all the mysteries.” (Thomas, 1980)
3. In Chapter 1, there are fourteen examples of the many questions that
may be answered when one considers the likelihood of odorous human
communication. Most of these questions concern different aspects of
human sexuality. Briefly deliberated are concerns about an ineffective
“language of olfaction” and errors in the logic that has been used in
the past to deny the importance of odor in human sexuality. The
introductory focus then turns to biological consistency among species;
the common basis for scientific advancements; and the development of
the working hypothesis that odors are a primary influence on human
sexuality.
4. Chemical communication and its importance in other species from
insects to mammals is more fully detailed in Chapter 2. The term
pheromone is defined, with added emphasis of one basic causal
relationship, namely, that mammalian pheromones appear to influence the
secretion of gonadotropin releasing hormone (GnRH), a hormone with both
short-term and long-term effects on neurotransmission. Distinguishing
characteristics of pheromones like species-specificity, and the
differences between signalling and releasing pheromones are added to
the definition. After a brief discussion of mammalian pheromones, the
natural production of human odors is discussed and anecdotal evidence
of some of their effects are offered as support for the concept of
human pheromones.
5. Chapter 3 alludes to Greek mythology; the story of Ariadne’s thread,
which metaphorically addresses the issue of biological consistency
among species. The development of the mammalian sense of smell is
detailed from its beginnings in single-celled organisms. Olfactory
transduction is briefly discussed. Four crucial turning points in the
development of mammalian chemical communication systems, which
contribute to species survival, are: (1) the release of pheromones to
attract another organism, which occurs in single-celled non-motile
organisms, (2) the ability to detect and respond to chemical messengers
with movement, which occurs in motile single-celled organisms (3) the
development of neural networks devoted to processing chemical signals,
which occurs in brainless invertebrates, and (4) phylogenetic advances
in the development of these neural networks to include development of
the vertebrate brain. Species-specific comparisons and contrasts in
structure and function are provided.
6. Chapter 4 offers an ontogenetic perspective on development, both of
the mammalian olfactory systems and of the GnRH neuronal system. The
ontogenetic connection between the structure and function of olfactory
sensory systems and brain development ascends in its significance
because it allows the odorous social environment to directly and
indirectly influence brain function by acting on GnRH, which in turn
has short-term effects on neurotransmission and long-term effects on
the hypothalamic-pituitary-gonadal (HPG) axis.
7. Kallmann’s syndrome represents a failure of GnRH neuronal
migration. Correlates with anosmia and the inability to fall in love
are noted, as are correlates with the GnRH neuronal system and brain
development in other species. Additional aspects of olfactory
transduction and signal processing are discussed. There are differences
between the main olfactory system and the accessory olfactory system.
The importance of the vomeronasal organ (VNO) for pheromone detection
in other species and renewed interest in the recently confirmed
presence of the human VNO add to the argument for the influence of
odors on human sexuality.
8. Chapter 5 begins with anthropological folklore associated with odor
and human behavior and progresses to a discussion of empirical evidence
for this link. The metabolism of hormones into pheromones is noted.
Specifically addressed are experiments with putative human pheromones
and the likelihood of causal physiological and behavioral
relationships. Comparisons and contrasts among species again are
offered in this regard. The use of mammalian pheromones in fragrances
designed to enhance the sexual appeal of humans is examined. The
naturally occurring fragrance of musk, present in the secretions of
many species, is held in high regard for its universal sex-attractant
properties.
9. Chapter 6 reports on experiments with consciously processed human
odors, beginning with the classically-conditioned response of infants
to their mothers’ naturally-scented or artificially-scented breasts.
Olfactory imprinting and the importance of the mother-infant bond are
linked through non-human animal models to the development of neural
templates and the human “love map”. Aspects of odor hedonics are
detailed.
10. Children can determine the genetic sex of adults, and adults can
distinguish between different people using their sense of smell. The
importance of mammalian odors in aggression and in other contexts
besides the mother-infant bond suggests human correlates. Similarly,
clinical and anecdotal evidence that humans are culturally aware of
odor-associated customs enhances a more scientific approach to the link
between sex and the human sense of smell. Odors and fetishism are
linked. The natural superiority of women’s olfactory acuity and
specificity is linked to estrogen levels and to an important role in
female choice: What human beings lack in acuity they make up for in
powers of discrimination, which rival those of any other mammal.
11. Chapter 7 is a simplistic overview of prenatal GnRH neuronal system
development. Included are genetic predisposition and the importance of
GnRH pulsatility in the regulation of the HPG axis. This chapter
begins, however, with the importance of chemical communication between
ovum and spermatozoa and progresses through basic genetics,
neuroanatomy, endocrinology, and endocrine aspects of
neurotransmission. Postnatally, odor input is linked to human HPG axis
function. Pheromone input appears to be indirectly measurable in assays
of luteinizing hormone.
12. Beginning with the “nature” versus “nurture” controversy, Chapter 8
proceeds to the important issue of finding a link between the social
environment and genes. The likelihood that genes are involved both in
physiological and in behavioral cause and effect relationships is
detailed. The influence of pheromones on genes and on concurrent
neuroendocrine, reproductive system, and central nervous system
development is proposed.
13. Twin studies are discussed, as is recent evidence of master genes
that may allow chemical communication at the cellular level to play a
primary role in behavioral development and in sexual orientation.
Genetic conservation among species, specifically with regard to
chemical communication, is addressed. Enzymes and chemical responses
are linked with human behavior, as are genes and G protein-coupled
receptors through an example of familial precocious puberty. Correlates
between adrenal androgen metabolism, pheromone production, sexual
dimorphism in the human hypothalamus, and human sexual orientation are
offered.
14. Chapter 9 details aspects of human consciousness and of limbic
learning and memory. Olfaction plays a key role by providing input to
the medial preoptic area of the hypothalamus. Comparisons and contrasts
among species and among theories of consciousness are offered.
15. The importance of linking specialized research in diverse
disciplines is made known, namely, how a “gay gene” might influence
both human neuroanatomy and human sexuality. Dean Hamer has proposed
the following: “The most simple hypothesis would be that the Xq28 makes
a protein that is directly involved in the growth or death of neurons
in the INAH-3. Alternatively, the gene could encode a protein that
influences the regulation of this region by hormones.” (Hamer &
Copeland 1994).
16. Effects of pheromones on other species are favorably compared to
the effects of putative human pheromones. A consciously-processed odor
stimulus has been used as an adjunct to classically condition the human
immune response, thereby adding clinical significance to the effects of
odors.
17. Chapter 10 reveals evidence of odor-driven hormonal effects on
human behavior and on sexuality, again using cross-species comparisons
that link information provided in earlier chapters. Examples supporting
a link between pheromones and human sexuality are discussed. The “Law
of Propinquity” appears to be invalidated by experience with pheromones
that create more of a friendship or kinship bond, perhaps also creating
an antibond effect on love. There is evidence that humans mate for
genetic diversity on the basis of unconscious odor associations, and
that odors may be involved in the Coolidge effect.
18. The sources of human pheromones are detailed in Chapter 11, with a
discussion of the role of glandular secretions, fatty acids, bacteria,
skin cells, and the relationship between levels or ratios of sex
hormones and pheromone production. Important aspects of pheromone
distribution are then linked to intimate behavioral associations.
Androgenization appears to stimulate secretion of a more masculine
pheromone signature. Odors can be used in clinical diagnostics. The
inherent difficulties of human pheromone research are briefly
discussed.
19. Chapter 12 links human pheromones to various courtship behaviors
(e.g., dancing, kissing, et al.,) that appear to become progressively
more intimate with increasing exposure to pheromones. Stereotypic
attractive qualities (e.g., large breasts or hair color and
distribution) with anecdotal evidence of causal relationships between
pheromones, attraction, and intimacy are represented both positively
and negatively. Culturally, negative representations often appear to
correlate well with sexual repression. Racial differences in odor
production that may contribute to racial prejudice are briefly
addressed.
20. Included in Chapter 13 is a discussion of results from the National
Geographic Smell Survey. Data was collected from approximately one and
a half million people worldwide. Causes of anosmia and its link both to
genetics and to the GnRH neuronal systems are detailed, as are links
between damage to the VNO, age-related disorders, olfactory deficits,
and behavior.
21. Chapter 14 provides both a historical and a modern-day overview of
aromatherapy. Cultural differences in odor hedonics are explained by
odor-associated classical conditioning. The roles of chemicals now
known to function as human pheromones and of putative human pheromones
in fragrances for commercial use is discussed. A brief summation of
current research supporting the hypothesis that human pheromones are a
primary influence on human sexuality is provided.
22. I believe that “the pheromones of other mammals are the only
social-environmental stimuli to influence genes [in GnRH neurons].”
Accordingly, human pheromones are the most likely link between the
“nature” and the “nurture” of human sexuality. However, a typographical
error: insertion of “not” on page 189, in paragraph 2, line 4 (intended
to read as above) detracts from the concluding paragraphs.
REFERENCES
Thomas, L. (1980) Notes of a biology-watcher: on smell. New England
Journal of Medicine 302: 731-733.
Hamer, D. & Copeland, P. (1994) The Science of Desire, Simon &
Schuster: 163.
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Marts, S. A., & Resnick, E. (2007). Sex Differences and the FDA Critical Path Initiative: Society for Women’s Health Research.
Wizemann, T. M., & Pardue, M.-L. (2001). Exploring the Biological Contributions to Human Health: Does Sex Matter? Washington D.C.: National Academy Press.
