Based on Gregg Johnson, in Recovering Biblical manhood and womanhood, ch. 16.  1997.  Available online.

1. Ethological observations

Among most higher social mammals males

• are more aggressive
• take dominant leadership roles
• are more territorial and competitive
• are more reactive and less cautious

Females:

• are more involved in parenting
• tend to socialise more horizontally and equally with other females
• are cautious in mating, seeking out more dominant males
• are more concerned with parenting, nurturing and maintaing pair bonds
• are less confrontative and combative and more interested in building and maintaing social bonds
• are peacemakers, seeking conformity to group expectations

From anthropological studies:

• ‘Males are almost always the rule makers, hunters, builders, fashioners of weapons, workers in metal, wood, or stone.’
• ‘Women are primary care givers and most involved in child rearing. Their activities center on maintenance and care of home and family. They are more often involved in making pottery, baskets, clothes, blankets, etc. They gather food, preserve and prepare food, obtain and carry firewood and water. They collect and grind grain.’

2. Physiology (other than nervous system)

Males

• have higher metabolic rate
• convert more energy into muscle and circulating reserves
• have 50% more muscle bulk at age 18
• have denser, stronger bones, tendons and ligaments
• have more sweat glands and can dissipate heat faster
• retain significant advantage in sports requiring short bursts of strength
• have 30% greater lung capacity, larger hearts, higher red cell and haemoglobin levels
• have higher blood clotting factors
• have fewer sensory nerve endings in the skin
• have a more active digestive system, with larger teeth, more salivary glands and higher production of gastric acid.  Their circulating blood sugar, cholesterol and amino acids are higher.
• are more at risk from hypertension, heart attacks and strokes
• Males begin production of gonadal testosterone at about 6th week of gestation.  This has a significant effect on the development of many organ systems.  Until puberty, male testosterone level is 2-3 times that of female, rising to 15 times post-puberty.

Females

• convert more energy into stored fat
• have twice the amount body fat at age 18
• have a thicker layer of subutaneous fat, acting as insulation and energy reserve
• are near-equals with men in endurance sports
• have higher levels of white blood cells and other factors leading to greater resistance of infection
• Females produce twice the amount of oestrogen until puberty; 8-10 times thereafter (varying with the stage of the menstrual cycle).

Studies of castrated or oestrogen-treated males, and of males with Klinefelter’s syndrome (XXY), tend to support a biological, rather than a purely cultural, explanation for sex differences.

3. Peripheral nervous system

Females

• have more acute senses of touch, hearing, smell and taste
• have better colour discrimination, and can see better in dim light
• appear better able to read facial expression

Males

• are better able to see fine detail
• have better night vision

These differences are consistent with the historical roles of women and men, as nurturers and hunters respectively.

4. Limbic system

Includes the hypothalamus and amygdala and several other nuclei of the midbrain and lower forebrain.  Is the seat of drives and emotions, including hunger, thirst, sex, fight and flight.

Males

• have a lower response threshold, due to effect of testosterone.
• have higher levels of various forms of aggression
• tend to leave the family group after puberty
• are more prone to wanterlust and adventure-seeking
• are more likely to commit violent crimes (especially so in XYY syndrome, which is associated with a particularly high level of testosterone

Females

• have a higher response threshold, due to effect of oestrogen
• are more likely to remain in the family group bonded to their mother
• exhibit maternal aggression, which is particularly strong during lactation
• appear to have an innate disposition to bond with their babies
• tend to cradle babies using the left arm, positioning the child closest to the strongest heartbeat and thus reinforcing the comfort that was imprinted during gestation

5. Central nervous system

Given that:

‘The left hemisphere controls the right side of the body, written and spoken language, numerical calculation, logic, and reasoning. The right hemisphere controls the left side of the body and processes artistic and musical stimuli, visual spatial patterning, insight, imagination, and emotional responses.’

Males

• are characterised by lateral organisation of functions (i.e. across both hemispheres)
• suffer a greater incidence of aphasia following stroke
• have a less developed left hemisphere, associated with a higher incidence of dyslexia and stutter
• have a greater aptitude for maths and visual-spacial skills
• tend towards convergent, categorical, thinking, suitable for quick decision-making

‘The more lateralized male brain would be expected to be more single-minded, focused, less distractable, and perhaps less socially aware. This, coupled with the hot-wired limbic system, may increase males’ competitive, goal-setting, rule-making, hierarchical approach to social interaction.’

Females

• are less lateralised, with verbal and visual/spacial centres in both hemispheres
• are more able to retain or recover verbal skills following stroke
• have a larger brain relative to body weight
• have a larger corpus callosum
• have a greater aptitude for verbal and social skills
• tend towards divergent, holistic, thinking

6. Sex differences at birth

It is clear enough that both ‘nature’ and ‘nurture’ have a part to play in brain development and function.  However, evidence of sex differences at birth tends to strengthen the case for the importance of biological influences.

Female infants

• tend to focus more on faces
• vocalise more
• respond earlier to smells and sounds
• when learning to draw, tend to draw people subjects

Male infants

• orient more to objects, lights and toys
• are comforted more by patterned mobiles and ticking clocks
• develop speech later
• draw objects more than faces
• learn three-dimensional drawing earlier

Men whose mothers were treated with diethylstilbestrol during pregnancy tend to be less aggressive, less athletically coordinated, and less given to masculine interests.

Women whose mothers were given androgens during pregnancy tend to be more masculine in aptitude and behaviour (e.g. energetic, tomboyish behaviour).

7. Stress management

‘After long-term stress, higher social animals often react with these types of responses: (1) heightened aggressive behavior, particularly among males, often resulting in fighting and death, (2) elevated abuse and even eating of young, (3) homosexual behavior, (4) miscarriage of and reabsorption of fetuses, and (5) discontinuance of ovulation and infertility.  By many measures, human beings in modern societies are living in stressful conditions. Many of the same behavioral anomalies we see in animals have begun to manifest themselves in the human population.’

The reaction to stress is, however, somewhat different in males and females, both in humans and in higher social animals.

The initial response is the same in both males and females – an increase in metabolic rate and sensory responsiveness as a result of elevated adrenalin output.  After that, females produce more cortisol and oestrogen, together increasing the likelihood of depressive disorders.  Males, on the other hand respond to chronic stress by producing more testosterone, leading to a general hyper-reactivity, but at the cost of increased risk of cardiovascular disease.

Men and women tend to be stressed by different sorts of factors.

‘By virtue of their gifts in language, their more networked nervous system, their acuity of perception, and their patience, women are more comfortable with and gravitate to social interaction and communication. They have physiologies and temperament traits that prepare them uniquely for child care. Their maternal instincts and bonding facility are stronger. Breeches of relationships, especially within the family, are particularly stressful for females. Inability to have children or to provide basic needs for a child are also common sources of feminine stress. Women need a sense that their social sphere of significant others is intact. They find fulfillment in caring for others and meeting needs.’

According to Willard Harley:

‘Women are stressed and vulnerable to an extramarital affair when one of these five needs is not met in their marriages: (1) need for affection, (2) need for conversation, (3) need for honesty, (4) need for minimal financial well-being, and (5) need for family commitment.’

Men, on the other hand:

‘appear to be more stressed when frustrated in goal achievement or when they feel a lack of control of their surroundings. They are stressed when frustrated in sexual fulfillment or when they sense a lack of support or respect from their wife and family. Harley proposes five reasons why a man would violate his marriage and seek fulfillment in an affair: (1) lack of sexual fulfillment, (2) lack of recreational companionship, (3) lack of an attractive spouse, (4) lack of domestic support, and (5) lack of admiration.’

All of this is consistent with the biblical admonition for husbands to love their wives, and for wives to respect their husbands (Eph 5:28-32).

Comment

This whole approach is sharply disputed.   Not so much the biological data, but the implications for male and female behaviour.  My reading of the works of evangelical feminists suggests that they often neglect evidence of biological differences between males and females in order to (over-)emphasise their similarities.  Alternatively, they ‘acknowledge that differences exist, but…don’t believe they’re linked to God-ordained “roles.”’ (Source)

In the case of feminists generally, my impression is that there exists a deep suspicion of such biological evidence. They will use every possible stragety to pursue a critique which is, essentially, ideologically-driven.  In the words of Cliodhna O’Connor:

‘The way much research on sexual differentiation is conducted and communicated has come under intense criticism from scholars in both the natural and social sciences. Scrutiny of the evidence-base for many claims of sex difference produces plentiful examples of methodological weakness and interpretative bias. In particular, neuroscientific studies of sex difference

1. routinely presume a simplistic gender binary in research design and interpretation;
2. ignore large within-sex variation in favour of emphasising small differences between the sexes; and
3. privilege determinist biogenetic explanations for brain differences over the equally plausible explanation that plastic brains are shaped by systematically different sociocultural experience.’

(Numbering added.)

More specifically:

The hormone oxytocin has, in recent years, received considerable attention in relation to sex differences.

Johnson is careful to point out that cultural and environmental factors are by no means irrelevant in this discussion.

I suspect that the implications of the biological evidence summarised above have been suppressed by an overwhelming weight of concern about ‘gender stereotypes’.

These data describe trends and general characteristics.  Exceptions can always be found.

We should be wary about turning an ‘is’ into an ‘ought’.

This whole area is riddled with exaggerations and denials on both sides of the argument.  In public discourse, the adage that ‘men are from Mars, women are from Venus’ is still believed.

These considerations would tend, to most readers, to suggest an evolutionary link between humans and (higher) animals.  But such a link is unexplored in this article.

See also

Can brain biology explain why men and women think and act differently? Online.

Glenda Cooper – ‘Male’ and ‘female’ brains aren’t real: time to rethink gender stereotypes.  The Telegraph, 1 December 2015.  Online.

Cliodhna O’Connor – “Brain Study Confirms Gender Stereotypes”: How science communication can fuel modern sexism. Online.

Cliodhna O’Connor – Gender on the Brain: A Case Study of Science Communication in the New Media Environment. Online.