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How Does Biology Contribute to Making Us Male or Female?

Gender differences


What is the difference between "sex" and "gender"?

What is the difference between "sex" and "gender"? How does biology contribute to making us male or female?

Gender differences:

I think it is necessary to clarify before beginning to comment on the differentiation between genders in normality and pathology, to clarify the distinction between sex and gender. These two concepts are often interchanged, undifferentiated, and even used synonymously, although it is not entirely correct. Sex, on the one hand, involves a biological difference. Gender, on the other hand, involves a cultural difference. Sex would be the biological aspects, that is to say, "the given", and gender the cultural factors, that is to say, "the built".

Both terms are frequently confused since it is agreed that when analyzing sex in its multiple aspects, its roots in the biological are verified, although its development is framed by the social "Sex. Abnormalities in the biological determination of sex also called sexual differentiation, usually occur in a very early stage of embryonic development and give rise to pathologies generically called "intersex". Regarding psychological sex, that is, the awareness or perception of belonging to certain sex occurs at 2.5-3 years and usually coincides with anatomical sex.

Regarding sexual orientation, it is understood as such the sexual preference that is established in adolescence coinciding with the time when brain development is completed: heterosexual preference (98%) or homosexual (2%).

Neurobiological and anthropological aspects of sexual differentiation

The morphological and functional differences that exist between men and women begin with the establishment of the chromosomal gender, during fertilization, followed by gonadal differentiation and, finally, the manifestation during puberty of the definitive male or female phenotype. This is a complex process that results from the interaction between the genome and the environment and takes place during the development of each individual and culminates in the expression of the phenotype, including behavior. An acolyte fertilized by a pair of X chromosomes determines the female sex. In blastocyst formation, one of the two X chromosomes is globally inactivated in all somatic cells, by the action of the XIST / Xist gene. This inactivation, possibly, makes it possible to equalize the amount of functional genetic material present in both genders. The chromosome combination of the XX or XY sex pair directs development to ovaries or testes respectively. In humans, during the first two months of gestation, both genders develop identically. In the male, the SRY gene, located on the short portion of the Y chromosome, is responsible for testicular differentiation through a protein called Testicular Determining Factor (TDF). Subsequently, the development of secondary sexual characteristics influenced by androgens occurs. On the other hand, in the female gender, the absence of TDF determines the formation of the ovaries and the subsequent expression of their phenotype.

In other words, in recent years the gene called SRY has been identified in region 1 of the short arm of the Y chromosome, which has information for the synthesis of a determining factor of the testis, TDF. This factor causes the masculinization process of the human embryo to begin in the seventh week of gestation, activating in a cascade the genes that cause the transformation of undifferentiated embryonic gonads into fetal testes. Once these have formed, they begin to secrete the hormone testosterone, which directs the development of the urogenital tract and male genitalia by transforming the embryonic structures known as the Wolffian ducts and the labioscrotal prominences. Also, the Sertoli cells of that embryonic testicle produce the antimullerian hormone, which destroys the embryonic structures called Müllerian ducts from which female organs would be generated, such as the uterus, vagina, and fallopian tubes, if of the chromosome And no back-up instructions will emanate.

For a long time it was thought that female development was not genetically determined, that is, Eve would only be NO Adam, It was believed that the differentiation of the zygote towards the female type was the spontaneous form, while the male development would come to be as a correction of this, due to the instructions written in the genes of the Y chromosome, however, recent data have made it possible to know that female differentiation is not a default differentiation, but that there is an embryogenetic pathway for the development of the ovary, parallel to the pathway commented for the development of the testicles. In 1994, the existence of a region of the ODF X chromosome was described, which favors the development of the ovary and inhibits the development of the testis. This zone would contain the genes for femininity, designated as Od or DSS. Once the ovary is formed in the female embryo, it begins to synthesize and secrete estrogens that direct the differentiation of the Müllerian duct and the labioscrotal prominences towards the female sexual organs.

There are therefore two perfectly differentiated pathways in the normal sexual development of the male or female embryo. In the Central Nervous System (CNS) the hormonal secretions of each sex in the early stages of embryonic development are largely the cause of the differences that affect it, being able to place them in three levels: cellular or synaptic ultrastructural differences, differences in organization synaptic or dendritic, and differences in the volume of defined groups of cells.

Nuclei with sexual dimorphism have been described in the human hypothalamus.

Le Vay's works are the best known and in them he shows that there is a NIH3 cell group (the third interstitial nucleus of the hypothalamus) that triples in men the size it presents in women; and in homosexuals, the NIH3 was the same size as in women. The preoptic region of the hypothalamus (SDNPOA) is the brain structure that shows a more noticeable generic dimorphism, with the size and number of cells in men being twice that in women of the same age. Differences were also found at the hypothalamic level. The volume of the posteromedial component of the nucleus of the stria terminalis bed (BNST-dspm) is two and a half times greater in men, and the suprachiasmatic subnucleus, which contains vasopressin, is more spherical in men and longer in women.

Women have more fibers in the corpus callosum and the anterior commissure (33%).

The man, on the other hand, needs "to lower the volume of the television to be able to answer the telephone. It is striking that male homosexuals also present greater interhemispheric communication than the rest of their peers. Perhaps, this fact is due to estrogen supplementation that takes place throughout life. To the differences at the ultrastructural, synaptogenic, and morphological levels, the influence of the environment must be added, as will be mentioned, determining differential psychological and behavioral aspects.

The main cognitive differences between men and women are manifested more in very specific activity patterns, not showing significant differences in terms of intelligence quotient (IQ).

Men, on average, perform better some spatial-type tasks such as tests that require imagining the rotation of an object or manipulating it in another way. They also outperform women in tests of mathematical reasoning and in taking trips following a certain route. For their part, women have greater perceptual speed and greater verbal fluency. They perform better in mathematical calculation tasks, remember the details of a given route better, and are faster at doing some precision manual work. They also have a better significance of facial expression and face recognition.

These differences are found in all cultures studied and are the result of exposure to androgens during prenatal development, but also vary with seasonal and diurnal fluctuations in sex hormones. In the same woman, differences are observed between the follicular phase with high levels of estrogens, associated with a facilitation of articulatory and fine motor efficiency, and the premenstrual or menstrual phase, with low estrogen levels, in which facilitation of the ability is observed space.

Women outperform men in perceiving fine visual details, in understanding the meaning of the facial expression, in recognizing faces, and in identifying the affective implications of the tone of voice. All these depend, basically, on the activity of the right hemisphere. This is not a sufficient reason to adduce a hemispheric functional difference between the two genders, but the cognitive differences strongly suggest that the intrahemispheric organization is different in each gender. To further clarify these concepts, we will detail the hemispheric functions and their differences. What follows is taken, almost verbatim, from a pioneering work by Jorge Forero, an excellent Colombian psychiatrist, and a great friend.

The main characteristic of the left hemisphere is the linguistic activity since this hemisphere controls linguistic behavior in its sensorimotor and audio verbal conditions. Also, it is where the prepositional language is elaborated, the words are emitted, the written expression is controlled, the capacity for numerical calculation and mathematical reasoning. It is also the dominant hemisphere of abstract verbal thinking. The left hemisphere controls the rational and abstract thinking of the subject, being dominant in activities that require the use of logical-deductive strategies in solving problems. It is the hemisphere where a preferentially analytical type of processing is carried out, especially in sequential and serial tasks. Analyzes time and perceives in detail, encodes sensory inputs in terms of linguistic descriptions, and lacks synthesizing ability. It prevails in verbal memory activities and is responsible for learning complex motor functions.

Meanwhile, the right cerebral hemisphere intervenes in literary creativity, in the melodic intonation of the language, identifies nouns and adjectives but not verbs, has little ability to read, and none to write. It is the hemisphere where the visual and geometric space is analyzed, through which we recognize faces (prosopagnosia), it is dominant in the perception of musical melodies, noises, and non-verbal sounds, it allows us to know objects through touch (stereognosis). He has been made responsible for creative artistic functions, specializes in the perception and expression of emotions, and controls gross motor activities and facial mimicry.

Anatomical differences of the female brain

As we said, the corpus callosum of women is comparatively larger than that of men and is the information channel that connects the cortical areas of the two hemispheres. The cerebral cortex is where higher cognitive functions are located. The right cerebral hemisphere is more emotionally sensitive, and through the rich pool of interhemispheric neurons located in the corpus callosum, information can be passed to the left cerebral hemisphere which is more analytical and where language resides. It appears that the corpus callosum allows emotions to be incorporated into the speech and thought processes.

The anterior commissure turns out to be more voluminous, this could explain why women seem to be more aware of their own emotions and those of others. The intermediate-mass that connects the two halves of the thalamus is also more voluminous in women. When women are asked to think of something sad, they generate more activity in the emotional hemisphere than men. The loss of functionally active neurons in the frontal and parietal lobes in women can lead to irritability and other personality changes. Women tend to lose more neurons in the hippocampus and parietal areas that have to do with memory and visuospatial skills, so they may have more difficulty remembering things and orienting them as they age. Girls have a greater aptitude for verbal and linguistic learning. The percentage of girls with difficulty in learning to read and write is lower and they learn to read more easily. Women are more proficient in comprehensive and expressive language tasks, and verbal creativity. Brain maturation rates are faster in women, which is why they have greater efficiency in language. They obtain better results in tests of verbal fluency, lower incidence of dyslexia, and delay in language acquisition.

When it comes to performing mental tasks, including dangerous situations, women have an innate condition that allows them to use both hemispheres of the brain simultaneously, configuring a functioning pattern that enables a greater area of ​​thought to be involved in their reasoning, which can be interpreted as the breadth of vision of life. This ancestral ability, coming from times in which humanity could be sedentary, made women, taking into account their physical condition, choose to be a farmer and gatherer, a job that transgenerationally earned her the acquisition and development of a broad vision for select and collects ripe fruits efficiently. Women consider a greater number of analysis variables when comparing two ideas to know and determine their relationships. They take into account a greater number of aspects in decision making. Her thought processes generally follow the circular operating pattern, which allows her to "hook" into her reflections several variables that make her judgments careful, detailed in detail, and guarantee a thorough review of possibilities. This capacity is used to add details contained in multiple memory files of both cerebral hemispheres in full exercise of their inferences to nourish their speech of details.

The woman can access countless files that contain information formatted by individual experiences, which are distributed throughout the cerebral cortex. This ability makes it easier for her to read the content of the brain folders contained in her files with unusual agility and to recruit an immense amount of information for the elaboration of ideas and therefore for the emission of her concepts. The way he conceives is subject to biological conditions and accumulated experience.

The understanding that she gives to her experiences is necessarily given by the exercise of contrasting the present experience with the information stored in previously formatted files and her thought expressed in words, it is the product of a complex process in which her entire cerebral cortex intervened. . Their opinions and judgments involve neural actions that engage wide areas of the cortex. Consult a greater number of files to make a decision and involve in it, all your higher cognitive functions. Examined the circumstances, the woman sets in motion an infinite network of brain circuits that transmit the most diverse information, mediated by the exquisite functioning of the neuronal synapse, with its component of neurotransmitters, neuroreceptors, and biochemical mediators to reach the brain files contained in the cerebral cortex of both hemispheres. There, it consults the information contained in the folders to produce an answer, from the simplest to the most complex. The acuity of her sentences is preceded by this complex operation.

Anatomical differences in the human brain

The man, as we said, has the preoptic nucleus of the hypothalamus 2.5 times larger, a nucleus that is responsible for typical male sexual behavior, which contains cells that are sensitive to androgens. Man is more prone to losing neurons in the frontal and temporal lobes in their natural aging process, these lobes are committed to thinking and feeling.

Functional differences in the human brain

Men turn out to be better in matters of mathematical reasoning, especially in geometry and mathematical language, as well as in tests that imply distinguishing between figure and ground, they have more facility to turn objects mentally, they are more effective in map interpretation and spatial perception. They more easily focus on a task, better detect a specific shape embedded within a complex pattern, and have better target shooting. Their male ancestors, hunters par excellence, had to learn to focus a point in space to hit the spear, arrow, or stone and be able to kill the animal while ignoring the environment. He spent generations training to develop and maintain tubular vision.

Male thinking tends to be unihemispheric and depending on dominance, their thought processes will be marked by the function of the dominant hemisphere. Taking into account that 93% of men are right-handed, the dominant hemisphere is the left one through which it handles logical processes, makes analytical inferences and deductions follow the linear thought model by a flow chart, thus adhering to the classic stimulus pattern- answer.

The number of consulted files, where the folders with the formatted information are found, turns out to be less in quantity and their answers are based on the information accumulated in the dominant hemisphere. In general terms, it involves fewer brain pathways through which it transmits the collected information in its thought processes. Use memory files as references to answer the present experience. If the current experience has characteristics similar to the one already formatted, issue a response that is similar to that obtained for previous experiences. The limited number of consulted files, which he uses as references, makes man especially predictable; the variety of responses to events of the same nature is less.

Remembering details turn out to be a costly exercise for the male brain, its memory files do not contain the minor details of previously formatted events, which is reflected when it comes to issuing its ideas and, given this limitation, it opts for more aggressive responses, giving Clear signs of the impact of hormonal influence, especially at the expense of testosterone.

Man, in general, has speeches with more concrete content; his linguistic creations contain fewer words and express his ideas more quickly. Look for speeches of practical results. The particularity of his logical and sequentially ordered thinking makes it more difficult for him to broaden his perspective. The ability to consult more files throughout the cerebral cortex is limited. Man is easily caught in a dead-end due to the difficulty of using new arguments that are efficiently articulated with his disciplined thought processes.