Tuesday, August 2, 2016
Biology and Gender
Sexual Reproduction in Humans "The human genome consists of two copies of each of 23 chromosomes (a total of 46). One set of 23 comes from the mother and one set comes from the father. Of these 23 pairs of chromosomes, 22 are autosomes, and one is a sex chromosome. There are two kinds of sex chromosomes- "X" and "Y". In humans and in almost all other mammals, females carry two X chromosomes, designated XX; and, males carry one X and one Y, designated XY." 1. "A human egg contains only one set of 23 chromosome and is said to be haploid. When an egg and sperm fuse at fertilization, the two sets of chromosomes come together for form a unique "diploid" individual with 46 chromosomes." 2. (Sex Differences in Humans- Wikipedia). "The sex chromosome in a human egg is always an X chromosome since a female only has X chromosomes. In sperm, about half the sperm have an X chromosome and half have a Y chromosome. If an egg fuses with a sperm with a Y chromosome, the resulting individual is usually male. If the egg fuses with a sperm with an X chromosome, the resulting individual is usually female. An egg's sex chromosome is always an X so it is the sperm's sex chromosome that determines an individual's sex. There are rare exceptions to this rule in which, for example, XX individuals develop as men or XY individuals develop as females." 3. "In mankind, the sex of an individual is generally determined at the time of fertilization by the genetic material carried in the sperm cell. If a sperm cell carrying an X chromosome fertilizes the egg, the offspring will typically be female (XX); if a sperm cell carrying a Y chromosome fertilizes the egg, the offspring will typically be male (XY)." 4. "The SRY gene on the Y chromosome interferes with the process of creating a female, causing a chain of events that leads to testes formation, androgen production, and a range of both natal and post-natal hormonal effects." 5. "Persons whose anatomy or chromosomal makeup differ from this pattern are referred to as intersex. This is referred to as the XY sex-determination system and is typical of most mammals, but quite a few other sex-determination systems exist, including some that are non-genetic." 6. "The X-chromosome carries a larger number of genes in comparison to the Y-chromosome. In humans, X-chromosome inactivation enables males and females to have equal expression of the genes on the X-chromosome since females have two X-chromosomes while males have a single X and a Y chromosome. X-chromosome inactivation is random in the somatic cells of the body as either the maternal or paternal X-chromosome can become inactivated in each cell. Thusly, females are genetic mosaics. (Sex differences in humans-Wikipedia) This process is seen in all mammals and is, also, referred to as lyonisation ( after Mary Lyon who described the process in 1962). In the somatic cells of a developing female child, one of the X-chromosomes is shortened and condensed. The genes on this chromosome, therefore, can not be transcribed into an mRNA transcript and remain unread. These condensed structures can be seen as dark bodies under the microscope and and are commonly referred to as Barr bodies. In individuals with Klinefelter's syndrome (females:XXX, males:XXY) the extra X-chromosome is inactivated, resulting in two bar bodies." 7. Prominent Physical and Biological Differences Between Men and Women "A great deal is now known about the development of masculine characteristics and the process of sexual differentiation specific to the reproductive system of Homo Sapiens." 8. "Humans exhibit sexual dimorphism (two forms)(a term for the phenotypic differences between the males and females of the same species) in many characteristics, many of which have no direct link to reproductive ability, although most of these characteristics do have a role in sexual attraction. Most expressions of sexual dimorphism in humans are found in height, weight, and body structure, though there are always examples that do not follow the overall pattern. Obvious differences between men and women include all the features related to reproductive role, notably the endocrine (hormonal) systems and their physical, psychological and behavioral effects. For example, men tend to be taller than women but there are many people of both genders who are in the mid-height range for the species. Some examples of male secondary sexual characteristics in humans, those acquired as boys become men or even later in life are: 1. More pubic hair 2. More facial hair 3. Larger hands and feet than women 4. Broader shoulders and chest 5. Greater muscle mass 6. A more prominent Adam's apple and deeper voice 7. A longer shinbone." 9. Size, weight, and body shape "Externally, the most sexually dimorphic portions of the human body are the chest, the lower half of the face, and the area between the waist and the knees. Males weigh about 15% more than females, on average. For those older than 20 years of age, males in the US have an average weight of 86.1 kg (190 lbs). Whereas, females have an average weight of 74 kg (163 lbs). On average, men are taller than women, by about 15 cm ( 6 inches) American males who are 20 years of age or older have an average height of 175.8 cm ( 5.9 in). The average height of corresponding females is 162 cm ( 5 ft 4 in). On average, men have a larger waist in comparison to their hips (waist-hip ratio) than women. Women have a larger hip section than men, an adaption for giving birth to infants with large skulls. (Wikipedia-Sex Differences in Humans) Although sex is a binary dichotomy, with "male" and "female" representing opposite and complementary sex categories for the purpose of reproduction, a small number of individuals have an anatomy that does not conform to either male or female standards or contains features closely associated with both. Such individuals, described as intersexuals, are sometimes infertile but are often capable of reproducing." 10.(Wikipedia-Sex Differences in Humans) "The most obvious differences between males and females include all the features related to the reproductive role, notably the endocrine (hormonal) 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." 11. (Wikipedia- Sex Differences in Humans) "The male reproductive system includes the penis, testicles, scrotum, prostate and other organs." 12. Skeletal and Muscular System Strength, Power and Muscle Mass "On average, males are physically stronger than females. The difference is due to females, on average, having less total muscle mass than males; and, also, having lower muscle mass in comparison to total body mass. While individual muscle fibers have similar strength, males have more fibers due to their greater total muscle mass. The greater muscle mass of males is, in turn, due to a greater capacity for muscular hypertrophy as a result of men's higher level of testosterone. Males remain stronger than females when adjusting for total body mass. This is due to the higher male muscle-mass to body-mass ratio. (Wikipedia- Sex Differences in Humans). As a result, gross measurements of body strength suggest an average 40-50% difference in upper body strength between the sexes as a result of this difference and a 20-30% difference in lower body strength. This is supported by another study that found that females are about 52-66 percent as strong as males in the upper body and about 70-80 percent as strong in the lower body. One study of muscle strength in the elbows and knees- in 45 and older males and females-found the strength of females to range from 42 to 63% of male strength." 13. (Sex Differences in Humans-Wikipedia) Skeleton "1. Males, on average, have denser, stronger bones, tendons, and ligaments. 2. In men, the second digit (index finger) tends to be shorter than the fourth digit (ring finger). While, in women, the second digit tends to be longer than the fourth. 3. Men have a more pronounced "Adam's Apple" or thyroid cartilage (and deeper voices) due to larger vocal cords. 4. On average, men have longer canine teeth than women. 5. Male skulls and head bones have a different shape than female skulls. One difference is in the roundness of the eye cavities. Another is the male's bony brow. Another is the shape of the jaw. 6. Male and female pelvises are shaped differently. The female pelvis features a wider pelvic cavity which is necessary when giving birth. The female pelvis has evolved to its maximum width for childbirth. An even wider pelvis would make women unable to walk. In contrast, human male pelves did not evolve to give birth and are, therefore, slightly more optimized for walking. The female pelvis is larger and broader than the male pelvis which is taller, narrower, and more compact. The female inlet is larger and oval in shape. While the male inlet is more heart shaped. 7. Contrary to popular belief, however, males and females do not differ in the number of ribs. Both have twelve pairs." 14. (Sex Differences in Humans-Wikipedia) Respiratory System "Males typically have larger tracheae and branching bronchi, with about 56 greater lung volume per body mass. They, also, have larger hearts, 10 percent higher red blood cell count, and higher haemoglobin, hence greater oxygen- carrying capacity. They, also, have higher circulating clotting factors (Vitamin K, prothrombin and platelets). These differences lead to faster healing of wounds and higher peripheral pain tolerance." 15. (Sex Differences in Humans-Wikipedia) Skin and Hair Skin "Male skin is thicker (more collagen) and oiler (more sebum) than female skin. The skin of females is warmer on average than that of males. Females tend to have more pain receptors per cm of skin than males." 16. Hair "On average, males have more body hair than females. Males have relatively more of the type of hair called terminal hair, especially on the face, chest, abdomen and back. In contrast, females have more vellus hair. Vellus hairs are smaller and, therefore, less visible. Baldness is much more common in males than in females. The main cause for this is male pattern baldness or androgenic alopecia. Male pattern baldness is a condition where hair starts to get lost in a typical pattern of receding hairline and hair thinning on the crown. It is causes by hormones and genetic predisposition. 17. (Sex Differences in Humans-Wikipedia) Color "On average and after the end of puberty, males have darker hair than females and , according to most studies, they, also, have darker skin (male skin is, also, redder but this is due to greater blood volume rather than melanin). Male eyes are, also, more likely to be one of the darker eye colors. Conversely, women are lighter-skinned than men in all human populations. The differences in color are mainly caused by higher levels of melanin in the skin, hair and eyes in males. In one study, almost twice as many females as males had red or auburn hair. A higher proportion of females were also found to have blond hair, whereas males were more likely to have black or dark brown hair. Another study found green eyes, which are the result of lower melanin levels, to be much more common in women than in men by at least a factor of two. However, a more recent study found that while women, indeed, tend to have a lower frequency of black hair, men, on the other hand, had a higher frequency of red-blond hair, blue eyes and lighter skin. According to one theory, the cause for this is a higher frequency of genetic recombination in women than in men, possibly due to sex-linked genes, and as a result, women tend to show less phenotypical variation in any given population. Also, women tend to bleach or color their hair while men tend not to which would make the population of blond or red-haired women seem higher than what it is naturally. The human sexual dimorphism in color seems to be greater in populations that are medium in skin color than in very light or very dark colored populations." 18. (Sexual Differences in Humans-Wikipedia) Sexual Organs and reproductive systems "Men and women have different sex organs. Women have two ovaries that store the eggs and a uterus which is connected to the vagina. Men have testicles that produce sperm. The testicles are placed in the scrotum behind the penis. The male penis and scrotum are external extremities whereas the female sex organs are placed "inside" the body. Men's orgasm is nearly essential ( "nearly" as small groups of sperm can escape the penis before orgasm is reached) for production whereas female orgasm is not. The female orgasm was believed to have no obvious function other than to be pleasurable, although some evidence suggests that it may have evolved as a discriminatory advantage in regard to mate selection." 19. (Wikipedia- Sex Differences in Humans) Reproductive capacity and cost "Men typically produce billions of sperm each month many of which are capable of fertilization. Women typically produce one egg a month that can be fertilized into an embryo. Thus, during a lifetime, men are able to father a significantly greater number of children than women can give birth to. The most fertile woman, according to the Guinness Book of World Records, was the wife of Feodor Vassilyev of Russia (1707-1782), who had 69 surviving children. The most prolific father of all time is believed to be the last Sharifian Emperor of Morocco, Mulai Ismail (1646-1727) who reportedly fathered more than 800 children from a harem of 500 women." 20. Fertility "Female fertility declines after age 30 and ends with menopause. Pregnancy in the 40s or later has been associated with increased chance of Down's Syndrome in children. Men are capable of fathering children into old age. Parental age effects in the children include multiple sclerosis, autism,breast cancer, schizophrenia, and reduced intelligence. Adriana Ilescu was reported as the world's oldest woman to give birth at age 66. Her record stood until Maria del Carmen Bousada de Lara gave birth to twin sons at Sant Pau Hospital in Barcelona, Spain on December 29, 2006, at the age of 67. In both cases, IVF (In Vitro Fertilization) was used. The oldest known father was former Australian miner Les Colley who fathered a child at age 93." 21. (Sex Differences in Humans-Wikipedia) The Brain and Nervous System "Both genes and hormones affect the formation of human brains before birth as well as the behavior of adult individuals. Several genes that code for differences between male and female brains have been identified. In the human brain, a difference between the sexes was observed in the transcription of the PCDH11X/Y gene pair, a pair unique to Homo sapiens." 22. "Using brain mapping, it was shown that men have more than six times the amount of grey matter related to intelligence than women, and women have nearly ten times the amount of white matter related to intelligence than men." 23. "Notably, male brains contain about 6.5 times more gray matter--sometimes called "thinking matter" --than women. Female brains have more than 9.5 as much white matter, the stuff that connects various parts of the brain than male brains. That's not all. "The frontal area of the cortex and the temporal area of the cortex are more precisely organized in women, and are bigger in volume, "Geary tells WebMD. This difference in form may explain a lasting functional advantage that females seem to have over males: dominant language skills." 24. "Gray matter is responsible for processing information in the brain and white matter 'represents the connections between these processing centers,' according to the study. These differences might explain why men ' excel in tasks requiring more local processing like mathematics-while women tend to excel at integrating and assimilating information.' Women tend to process more information in their frontal lobes but this activity is dispersed through the male brain. ' " 25. "Other differences that have been established include greater length in males of myelinated axons in their white matter (176,000 km compared to 146,000 km); and 33% more synapses per mm (cube) of cerebral cortex. Another difference is that females, generally, have faster blood flow to their brains and lose less brain tissue as they age than males do." 26. "The amygdala, which is the structure that responds to emotionally arousing information, responds to the environment and reacts with stress.The male amygdala is proportionately larger in men than in women causing sex to be a determining factor in reactions to stress. In studies of rats, there are more numerous interconnections seen in males in regard to this structure, suggesting the same pattern in humans." 27. "The hippocampus is proven by imaging to be larger in women than men. The hippocampus is crucial for memory storage and spatial mapping of the physical environment. A difference in behavior shown may be because of this particular structure variation between the sexes. Studies show that women are more likely to navigate using land marks while men are more likely to estimate distance in space or orientation.----- Chronic stress is dealt with better by females." 28. "It has been argued that the Y chromosome is primarily responsible for males being more susceptible to mental illness. Several psychological studies contradict this, however, as it has been found that women are, actually, more than twice as likely as men to be susceptible to depressive episodes and generalized anxiety and additionally that progesterone levels in females actually stall the body's ability to turn off stressor hormones resulting women entering depressive episodes at even lower levels of stress than men." 29. (Wikipedia- Sex Differences in Humans) "There is a mean difference in mean IQ in favor of men of about 5 points. The further you go up the distribution the more skewed it becomes. There are twice as many men with an IQ of 120 plus as there are women, There are 30 times the number of men with an IQ of 170-plus as there are women." 30. (Irwing 2006) "Almost 40,000 selected seventh-grade students from the Middle Atlantic region of the United States took the College Board Scholastic Aptitude Test as part of the Johns Hopkins regional talent search in 1980, 1981, and 1982. A separate nationwide talent search was conducted in which any student under age 13 who was willing to take the test was eligible. The results obtained by both procedures establish that by age 13 a large sex difference in mathematical reasoning ability exists and that it is especially pronounced at the high end of the distribution: among students who scored greater than or equal to 700, boys outnumbered girls 13 to 1. Some hypothesized explanations of such differences were not supported by the data." 31. "IQ stands for intelligence quotient. Supposedly, it is a score that tells one how "bright" a person is compared to other people. The average IQ is by definition 100. Scores above 100 indicate a higher than average IQ. Scores below 100 indicate a lower than average IQ. Theoretically, scores can range any amount below or above 100; however, in practice,they do not meaningfully go much below 50 or above 150. Half of the population have IQ's of between 90 and 110. Twenty five percent have higher IQ's and twenty five percent have lower IQ's. Descriptive Classification of Intelligence Quotients IQ Description % of Population 130 plus Very Superior 2.2% 120-129 Superior 6.7% 110-119 High average 16.1% 90-109 Average 50% 80-89 Low average 16.1% 70-79 Borderline 6.7% Below 70 Extremely low 2.2% Apparently, the IQ gives a good indication of the occupational group that a person will end up in, though not, of course, the specific occupation. In their book, Know Your Child's IQ, Glen Wilson and Diana Grylls outline occupations typical of various IQ levels: 140 Top Civil Servants; Professors and Research Scientists. 130 Physicians and Surgeons; Lawyers; Engineers (Civil and Mechanical). 120 School Teachers; Pharmacists; Accountants; Nurses; Stenographers; Managers. 110 Foreman; Clerks; Telephone Operators; Salesmen; Policemen; Electricians. 100 plus Machine Operators; Shopkeepers; Butchers; Welders; Sheet Metal Workers. 100 minus Warehouse men; Carpenters; Cooks and Bakers; Small Farmers; Truck and Van Drivers. 90 Laborers; Gardeners; Upholsterers; Farm hands; Miners; Factory Packers." 32. Given the relative and absolute number of men in the higher IQ ranges, one would expect a disproportionate relative and absolute number of men in those occupations associated with the same. However, feminists, jurists, and the political body of the USA and other nations have unjustly attributed this disparity to intentional and or unintentional gender discrimination against women. Dramatic Orwellian Affirmative action and other overt and covert programs to unjustly give women those educational and employment opportunities that justly, because of both ability and effort, belong to men have resulted in significant decreases in productivity and efficiency through out the American economy and those of other nations which had adapted these authoritarian and Machiavellian precepts. Associated with the same are socio-cultural break down and decreased and/or stagnant average incomes, income growths, job security, the average wealth of all Americans, and well as the stagnation of and/or decline of other economic indicators. All male fitness and well being indicators are in a drastic decline. Though all aspects of male health and well being are in decline, there is no Council On Men and Boys nor a Federal Office On Mens Health while women now have at least seven.
Posted by Marcus Aurelius at 8:10 PM