Social-Neuroscience-of-Sex.pdf

Social Neuroscience of Sex;

Human Male-Female Similarities and Differences from Neurological

Biochemistry to Social Behavior

Jonathan Cachat

Denison University ‘08

Dr. Susan Kennedy – Dr. Kristina Mead – Dr. Frank Hassebrock

 Jonathan Cachat 2008

Table of Contents 

1 – Introduction ...........................................................................................................4  

2 – A Brief Intellectual History of Science .....................................................................7  

2.1 – The ‘Two‐Cultures’ ...................................................................................................................................... 11  

2.2 – The Middle Ground ..................................................................................................................................... 16  

2.2.1 – The Natural Sciences ............................................................................................................................... 17  

2.2.2 – The Social Sciences ................................................................................................................................... 19  

2.3 – Meeting at the Brain ................................................................................................................................... 23  

3 – Social Neuroscience..............................................................................................25  

3.1 – The Dialectical Model of Human Nature............................................................................................ 26  

3.2 – Conceptual and Methodological Issues .............................................................................................. 29  

4 – Orienting Concepts and Definitions ......................................................................33  

4.1 – The Mind and The Brain ........................................................................................................................... 33  

4.2 – Society and Culture ..................................................................................................................................... 34  

4.3 – Enculturation, Socialization, Indoctrination or Assimilation ................................................... 35  

4.4 – Sex and Gender ............................................................................................................................................. 36 

5 – Human Sexual Dimorphisms in CNS Anatomy and Physiology...............................37  

5.1 – Central Nervous System: Anatomy and Physiology...................................................................... 39  

5.2 – Cerebral Cortex: Anatomy and Physiology....................................................................................... 51  

5.2.1 – Microlevel: Anatomy and Connectivity within Cortical Layers............................................. 52  

5.2.2 – Macrolevel: Anatomy and Physiology of Cortical Areas .......................................................... 56  

5.3 – The Central Nervous System and Hormones................................................................................... 60  

6 – Sexual Reproduction.............................................................................................62  

6.1 – Evolutionary Theory & The Social Dynamics of Sexual Reproduction................................. 62  

6.2 – Physiology of Sexual Reproduction ..................................................................................................... 67  

6.2.1 – Puberty .......................................................................................................................................................... 67  

6.2.2 – Orientation................................................................................................................................................... 69  

6.2.3 – Attraction ..................................................................................................................................................... 72  

6.2.4 – Arousal........................................................................................................................................................... 74  

6.2.5 – Climax............................................................................................................................................................. 76  

7 – Sexual Differentiation, Ontogenetic Development & Brain Evolution....................76  

7.1 – Sexual Differentiation ................................................................................................................................ 76  

7.1.1 – Intersex Syndromes .................................................................................................................................. 78  

7.2 – Neocortical Evolution ................................................................................................................................ 81  

7.3 – Cortical Development ................................................................................................................................ 87  

7.3.1 – Cortical Layers ........................................................................................................................................... 87  

7.3.2 – Cortical Networks ..................................................................................................................................... 88  

8 – Enculturation........................................................................................................90  

9 – Evolution & Phenomenology of Consciousness .....................................................91  

9.1 – Evolutionary Theory and The Feminine Role in Sexual Selection.......................................... 91  

9.2 – Natural History of Parenting Dynamics and The Reduction of Sexual Dimorphisms.... 94  

9.3 – The Elaboration of Social Cognition and The Emergence of Consciousness...................... 94  

10 – Conclusion ..........................................................................................................95  

Jonathan Cachat – www.jcachat.com - Social Neuroscience of Sex 2

11 – References..........................................................................................................95  

Cachat 3

1 – Introduction

Mars and Venus, Iron and Copper, Male and Female. Stereotypes that

characterize the genders have persisted throughout history, from archaic astronomy and

medieval alchemy through the present (Stearn, 1962). The Roman god of war, an

aggressive and physically strong warrior; the Roman goddess of love, beauty and

fertility depicted as fragile yet seductively powerful. Iron is strong and hard, forged into

weaponry; Copper is malleable yet sturdy, crafted into adornments.

Stereotypes, although broad generalizations, often do contain accurate

descriptions of observable differences in behavior and thought patterns across sex lines,

which have been studied and described by numerous academic disciplines. Gender

Archeology, interested in the differences between sex roles throughout ancient history;

Political Science, interested in predicting and influencing behavior and choice of either

sex; Women’s Studies, interested in studying women’s history and the feminine role in

contemporary society while shedding an androcentric intellectual inheritance; Gender

Studies, interested in the way society constructs and instructs ‘acceptable’ behavior for

both men, women and those do not prefer such strict classification; Feminist Philosophy,

Gender Anthropology, Sexual Psychology and even Sexual Biology. The combinations of

words for sex or gender paired with an academic discipline are practically endless, each

with their point of origin, intellectual traditions, and conventional tools or methodologies

aimed at teasing out the empirically validated from the pseudoscientific beliefs.

Knowledge of the similarities and differences between a human male’s and

female’s biology, behavior and psychology is in the end, quite important. Medical

procedures, pharmacological treatment or use, psychological counseling, product design

Jonathan Cachat – www.jcachat.com - Social Neuroscience of Sex 4

and marketing, career decisions, law enforcement – there are really few aspects of daily

life where the impact of sex or gender is not explicitly or implicitly evident.

Social neuroscience is an emerging academic discipline that has the potential to

offer great insight to the study of human sexual dimorphisms. The unique

interdisciplinary philosophy of social neuroscience emphasizes the synthesis of

knowledge, tools and methodologies from multiple and even

S EXUAL D IMORPHISM

A formally observed, statistically

verified difference in the biology,

behavior or cognition between

individual sexes within a species.

divergent academic disciplines in order to develop a

comprehensive and more accurate model of human nature and

sociality. As we learn more about the brain, one of the most significant insights social

neuroscience has already illuminated is that that strict and robust categories of male or

female may accurately distinguish reproduction organs, but may not be as applicable to

brain anatomy and physiology. Accordingly, Melissa Hines in Brain Gender (2004),

comments that although most humans are distinctly male or female, we are truly “each

complex mosaics of male and female characteristics” (Hines 2004, 19).

Embracing the ethos of social neuroscience, the goal of this research is to

combine knowledge and analyze research from biochemistry, evolutionary biology,

archeology, neuroscience, psychology, sociology, anthropology, political science,

economics and philosophy in order to establish the origin and existence of human sexual

dimorphisms. Using the Dialectical Model of Human Nature ( 3.1 ), I will trace the

prevalence sexual dimorphisms across Homo sapiens’ shared evolutionary, ( 7.0 ) and

social history ( 6.1 & 8.0 ) while paralleling this discussion to the ontogenetic

O NTOGENETIC

The development of an individual

from fertilization to death, as

contrasted with the development of

a group or species (phylogenetic)

development of sexually dimorphic traits ( 6.2, 7.0 ). I

will begin with an intellectual history of social

neuroscience in order to further elucidate the merits of

Cachat 5

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