Sex differences in humans

Sex determination occurs by the presence or absence of a Y in the 23rd pair of chromosomes in the human genome. 

Phenotypic sex refers to an individual’s sex as determined by their internal and external genitalia and expression of secondary sex characteristics.

Sex differences generally refer to traits that are sexually dimorphic, and such differences is hypothesized to be the product of the evolutionary process of sexual selection.

Sex differences in medicine include sex-specific diseases, which are diseases that occur only in people of one sex; and sex-related diseases, which are diseases that are more usual to one sex, or which manifest differently in each sex. 

Certain autoimmune diseases may occur predominantly in one sex, for unknown reasons. 90% of primary biliary cirrhosis cases are women, whereas primary sclerosing cholangitis is more common in men. 

Smptoms and responses to medical treatment may be very different between sexes.

Sex-related illnesses have various causes:

Sex-linked genetic illnesses.

Parts of the reproductive system that are specific to one sex.

Social causes that relate to the gender role expected of that sex in a particular society.

Different levels of prevention, reporting, diagnosis or treatment in each gender.

Sex differences in human physiology are the direct result of differences prescribed by the Y-chromosome, due to the SRY gene, and indirect being characteristics influenced indirectly by the Y-chromosome. 

Sexual dimorphism is a term for the genotypic and phenotypic differences between males and females.

Through the process of meiosis and fertilization each individual is created with zero or one Y-chromosome. 

The complementary result for the X-chromosome follows, either a double or a single X. 

Direct sex differences are usually binary in expression.

The most obvious differences between males and females include all the features related to reproductive roles, notably the endocrine systems and their physiological and behavioral effects, including gonadal differentiation, internal and external genital and breast differentiation, and differentiation of muscle mass, height, and hair distribution. 

There are differences in the structure of specific areas of the brain. 

The interstitial nucleus of the anterior hypothalamus (INAH33) has been repeatedly found to be considerably larger in males than in females.

A brain study done by the NIH showed that the females had greater volume in the prefrontal cortex, orbitofrontal cortex, superior temporal cortex, lateral parietal cortex, and insula, whereas males had greater volume in the ventral temporal and occipital regions.

Females typically have two X chromosomes while males typically have an X and a Y chromosome. 

The X chromosome is more active and encodes more information than the Y chromosome, which has been shown to affect behavior.

The X chromosome may contain a gene influencing social behaviors.

Most IQ tests are constructed so that there are no overall score differences between females and males. 

Areas where differences have been found include verbal and mathematical ability.

For grades 2 to 11, there were no significant gender differences in math skills among the general population.

Differences in variability of IQ scores have been observed in studies, with more men falling at the extremes of the spectrum.

Some differences are due to socially assigned roles (nurture), while other studies show that differences are due to innate inherent differences.

Stereotypes about differences between men and women have been shown to affect a person’s personality.

There are large differences in women’s and men’s preferences for realistic occupations (mechanic or carpenters) and moderate differences in their preferences for social and artistic occupations. 

Women tend to be more people-oriented and men more thing-oriented.

Many kinds of mental illnesses and behavioral problems show gender differences in prevalence and incidence. 

Of the 80 disorders diagnosed in adulthood for which sex ratios are provided, 35 are said to be more common in men than in women (17 of which are substance related or a paraphilia), 31 are said to be more common in women than men, and 14 are said to be equally common in both sexes.

Female jealousy is more likely to be inspired by emotional infidelity, male jealousy is most likely to be brought on by sexual infidelity: 

62% to 86% of women reported that they would be more bothered by emotional infidelity and 47% to 60% of men reported that they would be more bothered by sexual infidelity.

The gender similarities hypothesis, holds that that males and females are similar on most, but not all, psychological variables. 

The cognitive variables of reading comprehension, mathematics, communication (talkativeness, facial expressions), social and personality (aggression, sexuality), psychological well-being, and motor behaviors are similar among the genders: a review of 46 meta-analyses, found that 78% of gender differences are  small or close to zero. 

Some motor behaviors (such as throwing distance) and some aspects of sexuality (such as attitudes about casual sex), show the largest gender differences. 

Variations within genders are greater than variations between genders.

There is a significant female advantage in time on the lexicon  and on the temperament scale of social-verbal tempo, and a male advantage on the temperament scale of physical endurance which were more pronounced in young age groups and faded in older groups. 

A one-dimensional approach to sex differences overlooks a possible interaction of sex differences with age.

Men commit more criminal acts than women.

Self-reported delinquent acts are also higher for men than women across many different actions.

Evolutionary neuroandrogenic theory posits that sexual selection has led to increased exposure to testosterone in males, causing greater competitive behavior which could lead to criminality.

The difference in crime rates between men and women might be due to social and cultural factors, crimes going unreported, or to biological factors (testosterone or sociobiological theories). 

Men can have an overwhelming bias against reporting themselves to be the victims of a crime, particularly when victimized by a woman, and some studies have argued that men reporting intimate partner violence find disadvantageous biases in law enforcement.

Low levels of self control are associated with criminal activity.

Sex differences in educational achievement may be caused by sex discrimination in law or culture, or may reflect natural differences in the interests of the sexes.

Leadership positions continue to be dominated by men.

Sex differences in religion can be classified as internal or external.

Internal religious issues are studied from the perspective of a given religion, and include:  religious beliefs and practices about the roles and rights of men and women in government, education and worship; beliefs about the sex or gender of deities and religious figures; and beliefs about the origin and meaning of human gender. 

External religious issues are the examination of a given religion from an outsider’s perspective, including possible clashes between religious leaders and laity.

Religious perspectives have either endorsed or condemned alternative family structures, homosexual relationships, and abortion.

Sex differences in social capital relate to differences between men and women in their ability to coordinate actions and achieve their aims through trust, norms and networks.

There are highly asymmetric rates of suicide and suicide attempts between males and females: gender paradox of suicidal behavior.

Males die much more often by means of suicide than females do.

Numerous studies have found that women tend to be financially more risk-averse than men and hold safer portfolios.

Due to factors such as socialization, males are typically more likely to focus on self, upside potential, aggressiveness in investments, and females typically focus on others, downside potential, and nurturing, explaining many financial decision making outcomes.

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