→Skin and hair: reverting Blueeyedturk (again); please stop; this stuff is sourced to leading researchers in the field, your comment about blogspot is in error |
WeijiBaikeBianji (talk | contribs) →Color: When the paragraph text reads "one study found" repeatedly, the proper sourcing guideline is not being followed. Find some reliable secondary sources. |
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[[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, and is caused by hormones and genetic predisposition.<ref>[http://www.nlm.nih.gov/medlineplus/ency/article/001177.htm Male Pattern Baldness]</ref> |
[[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, and is caused by hormones and genetic predisposition.<ref>[http://www.nlm.nih.gov/medlineplus/ency/article/001177.htm Male Pattern Baldness]</ref> |
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=== Color === |
=== Color === |
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⚫ | 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 eyes are also more likely to be one of the darker eye colors. Conversely, women are lighter-skinned than men in all human populations.<ref name="frost3">Frost, P. (2007). [http://evoandproud.blogspot.com/2007/11/sex-linkage-of-human-skin-hair-and-eye.html Sex linkage of human skin, hair, and eye color]</ref> The differences in color are mainly caused by higher levels of [[melanin]] in the skin, hair and eyes in males.<ref name="frost1">Frost, P. (1988). Human skin color: A possible relationship between its sexual dimorphism and its social perception. Perspectives in Biology and Medicine, 32, 38–58.</ref><ref name="frost2">{{Cite journal | doi = 10.1016/j.evolhumbehav.2005.07.002 | last1 = Frost | first1 = P. | year = 2006 | title = European hair and eye color - A case of frequency-dependent sexual selection? | url = | journal = Evolution and Human Behavior | volume = 27 | issue = | pages = 85–103 }}</ref> 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.<ref name=OCA2>{{cite journal |author=Duffy DL, Montgomery GW, Chen W, ''et al.'' |title=A three-single-nucleotide polymorphism haplotype in intron 1 of OCA2 explains most human eye-color variation |journal=Am. J. Hum. Genet. |volume=80 |issue=2 |pages=241–52 |year=2007 |month=February |pmid=17236130 |pmc=1785344 |doi=10.1086/510885 }}</ref> Another study found [[green eyes]], which are a result of lower melanin levels, to be much more common in women than in men, at least by a factor of two.<ref name="frost3" /><ref>Patrick, S. et. al (2007). Genetic determinants of hair, eye and skin pigmentation in Europeans. Nature Genetics Published online: 21 October 2007 doi:10.1038/ng.2007.13</ref> 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 then in men and as a result women tends to show less phenotypical variation in any given population.<ref>http://onlinelibrary.wiley.com/doi/10.1111/j.1469-1809.2009.00504.x/abstract</ref><ref name="dienekes">[http://dienekes.blogspot.com/2009/02/interaction-between-loci-affecting.html Interaction between loci affecting human pigmentation in Poland]</ref> |
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⚫ | 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 eyes are also more likely to be one of the darker eye colors. Conversely, women are lighter-skinned than men in all human populations.<ref name="frost3">Frost, P. (2007). [http://evoandproud.blogspot.com/2007/11/sex-linkage-of-human-skin-hair-and-eye.html Sex linkage of human skin, hair, and eye color]</ref>{{primary source claim}} The differences in color are mainly caused by higher levels of [[melanin]] in the skin, hair and eyes in males.<ref name="frost1">Frost, P. (1988). Human skin color: A possible relationship between its sexual dimorphism and its social perception. Perspectives in Biology and Medicine, 32, 38–58.</ref><ref name="frost2">{{Cite journal | doi = 10.1016/j.evolhumbehav.2005.07.002 | last1 = Frost | first1 = P. | year = 2006 | title = European hair and eye color - A case of frequency-dependent sexual selection? | url = | journal = Evolution and Human Behavior | volume = 27 | issue = | pages = 85–103 }}</ref>{{primary source claim}} 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.<ref name=OCA2>{{cite journal |author=Duffy DL, Montgomery GW, Chen W, ''et al.'' |title=A three-single-nucleotide polymorphism haplotype in intron 1 of OCA2 explains most human eye-color variation |journal=Am. J. Hum. Genet. |volume=80 |issue=2 |pages=241–52 |year=2007 |month=February |pmid=17236130 |pmc=1785344 |doi=10.1086/510885 }}</ref>{{primary source claim}} Another study found [[green eyes]], which are a result of lower melanin levels, to be much more common in women than in men, at least by a factor of two.<ref name="frost3" /><ref>Patrick, S. et. al (2007). Genetic determinants of hair, eye and skin pigmentation in Europeans. Nature Genetics Published online: 21 October 2007 doi:10.1038/ng.2007.13</ref>{{primary source claim}} 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 then in men and as a result women tends to show less phenotypical variation in any given population.<ref>http://onlinelibrary.wiley.com/doi/10.1111/j.1469-1809.2009.00504.x/abstract</ref><ref name="dienekes">[http://dienekes.blogspot.com/2009/02/interaction-between-loci-affecting.html Interaction between loci affecting human pigmentation in Poland]</ref>{{primary source claim}} |
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== Sexual organs and reproductive systems == |
== Sexual organs and reproductive systems == |
Revision as of 02:26, 19 November 2010
A sex difference is a distinction of biological and/or physiological characteristics typically associated with either males or females of a species in general. This article focuses on quantitative differences which are based on a gradient and involve different averages. For example, males are taller than females on average,[1] but an individual female may be taller than an individual male.
Obvious differences between males and females include all the features related to reproductive role, notably the endocrine (hormonal) systems and their physiological and behavioural effects. Such undisputed sexual dimorphism include gonadal differentiation, internal genital differentiation, external genital differentiation, breast differentiation, muscle mass differentiation, height differentiation, and hair differentiation.
Sex Determination
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.
A human egg contains only one set of chromosomes (23) and is said to be haploid. Sperm also have only one set of 23 chromosomes and are therefore haploid. When an egg and sperm fuse at fertilization, the two sets of chromosomes come together to form a unique "diploid" individual with 46 chromosomes.
The sex chromosome in a human egg is always an X chromosome, since a female only has X sex 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 an 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 males or XY individuals develop as females.
Sexual dimorphism
- For information about how males and females develop differences throughout the lifespan, see sexual differentiation.
Sexual dimorphism (two forms) refers to the general phenomenon in which male and female forms of an organism display distinct morphological characteristics or features.
Sexual dimorphism in humans is the subject of much controversy, especially relating to mental ability and psychological gender. (For a discussion, see biology of gender, sex and intelligence, gender, and transgender.) 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. Although sex is a binary dichotomy, with "male" and "female" representing opposite and complementary sex categories for the purpose of reproduction, there are a small number of individuals whose anatomy does not conform to either male or female standards. Such individuals, called intersexuals, are sometimes infertile but are often capable of reproducing.
Some biologists[who?] theorise that a species' degree of sexual dimorphism is inversely related to the degree of paternal investment in parenting. Species with the highest sexual dimorphism, such as the pheasant, tend to be those species in which the care and raising of offspring is done only by the mother, with no involvement of the father (low degree of paternal investment). This would also explain the moderate degree of sexual dimorphism in humans, who have a moderate degree of paternal investment compared to most other mammals.
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.[2]
- 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).[3]
- On average, men are taller than women, by about 15 cm (half a foot).[1] American males who are 20 years old or older have an average height of 175.8 cm (5 ft 9 in). The average height of corresponding females is 162 cm (5 ft 4in).[3]
- On average, men have a larger waist in comparison to their hips (see waist-hip ratio) than women.[citation needed]
- On average, men have a greater capacity for cardiovascular endurance[citation needed]. This is due to the enlargement of the lungs of boys during puberty, characterized by a more prominent chest.[citation needed]
- Women have a larger hip section than men, an adaptation for giving birth to infants with large skulls.[citation needed]
Skeleton and muscular system
Strength, power and muscle mass
On average, males are stronger than females. The differences in strength are due to females, on average, having less total muscle mass than males. Females also have lower muscle mass in comparison to total body weight. Gross measures of upper body strength suggest an average 40-50% difference between the sexes, compared to a 30% difference in lower body strength.[4] In another, similar, estimate females are about 52 percent as strong as males in the upper body, and about 66 percent as strong in the lower.[5] 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.[6] Males are not stronger due to greater strength of individual muscle fibers, but due to more fibers: a 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 levels of testosterone. Males remain stronger than females, when adjusting for differences in total body weight. This is due to the higher male muscle-mass to body-weight ratio.[7]
The uterus—as it is a part of the female reproductive system—is a muscle found only in females. The uterus may be the single strongest muscle in comparison to body weight across both sexes.[citation needed]
Comparison between a male (left) and a female pelvis (right). |
Skeleton
- Males, on average, have denser, stronger bones, tendons, and ligaments.
- 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 (see digit ratio).[8]
- Men have a more pronounced 'Adam's Apple' or thyroid cartilage due to larger vocal cords (and deeper voices).[9]
- On average, men have longer canine teeth than women.
- Female skulls and head bones have a different shape than male skulls. One difference is in the roundness of the eye cavities, another is the male's bony brow, and a third difference is the shape of the jaw.
- 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 are not constrained by the need to give birth and are therefore more optimized for walking.[10] As a result, 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.[11]
- However, contrary to popular belief, males and females do not differ in the number of ribs; both have twelve pairs.[12]
Respiratory system
Males typically have larger tracheae and branching bronchi, with about 30 percent greater lung volume per body mass. They also have larger hearts, 10 percent higher red blood cell count, 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.[13]
Skin and hair
Skin
Male skin is thicker (more collagen) and oilier (more sebum) than female skin.[14]
The skin of females is warmer on average than that of males.
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, and is caused by hormones and genetic predisposition.[15]
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 eyes are also more likely to be one of the darker eye colors. Conversely, women are lighter-skinned than men in all human populations.[16][non-primary source needed] The differences in color are mainly caused by higher levels of melanin in the skin, hair and eyes in males.[17][18][non-primary source needed] 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.[19][non-primary source needed] Another study found green eyes, which are a result of lower melanin levels, to be much more common in women than in men, at least by a factor of two.[16][20][non-primary source needed] 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 then in men and as a result women tends to show less phenotypical variation in any given population.[21][22][non-primary source needed]
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.[16][non-primary source needed]
Sexual organs and reproductive systems
Men and women have different sex organs. Women have two ovaries that produce eggs, and uterus which is connected to a 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.
Reproductive capacity and cost
Men typically produce billions of sperm each month,[23] 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 67 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.
Fertility
Female fertility declines after age 30 and ends with the menopause.[24][25] Pregnancy in the 40s or later has been correlated with increased chance of Down's Syndrome in the children.[26] Men are capable of fathering children into old age. Paternal age effects in the children include multiple sclerosis,[27] autism,[28] breast cancer [29] and schizophrenia,[30] as well as reduced intelligence.[31] Adriana Iliescu 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 was used. The oldest known father was former Australian miner Les Colley, who fathered a child at age 93.[32]
Brain and nervous system
Brain
The brains of many animals, including humans, are significantly different for males and females of the species.[33]
Brain size
Human males, on average, have larger brains than females.
In 1861, Paul Broca examined 432 human brains and found that the brains of males had an average weight of 1325 grams, while the brains of females had an average weight of 1144 grams. More recently, a 1992 study of 6,325 Army personnel found that men's brains had an average volume of 1442 cm³, while the women averaged 1332 cm³. These differences were shown to be smaller but to persist even when adjusted for body size measured as body height or body surface, such that women averaged 100 g less brain mass than men of equal size.[34]
According to another estimate, on average, male brains have approximately 4 % more cells and weigh 100 grams more than female brains do. However, both sexes have a similar brain weight to body weight ratio. Female brains are more compact than male brains in that, though smaller, they are more densely packed with neurons, particularly in the region responsible for language.[35]
In studies concerning intelligence, it has been suggested that the ratio of brain weight to body weight is more predictive of IQ levels, rather than actual brain weight. While men's brains are an average of 10-15% larger and heavier than women's brains, some researchers propose that the ratio of brain to body size does not differ between the sexes.[36][37] However, some argue that since brain-to-body-size ratios tend to decrease as body size increases, a sex difference in brain-weight ratios still exists between men and women of the same size.[34]
Brain structure
There are also differences in the structure of and in specific areas of the brain. For instance, males have larger left inferior parietal lobes.[38] At the same time females have larger Wernicke's and Broca's areas, areas responsible for language processing.[39] Also, females may have their language functions more evenly distributed in both cerebral hemispheres, while in males they are more concentrated in the left hemisphere.[dubious ] This puts males more at risk for language disorders like dyslexia. Evidence of gender differences in the size of the corpus callosum is ambiguous.[citation needed]
A proposed alternative way of measuring intelligence is by using gray matter or white matter volume in the brain as an indicator. The former used for information processing, whereas the latter makes up the connections between processing centers. In 2005, Haier et al. reported that, compared with men, women show more white matter and fewer gray matter areas as related to intelligence.[40] Using brain mapping, it was shown that men have more than six times the amount of gray matter related to general intelligence than women, and women have nearly ten times the amount of white matter related to intelligence than men.[41] They also report that the brain areas correlated with IQ differ between the sexes. In short, men and women apparently achieve similar IQ results with different brain regions.[42]
In total and on average, females have a higher percentage of gray matter in comparison to males, and males a higher percentage of white matter.[43][44] However some researchers maintain that as males have larger brains on average than females, when adjusted for total brain volume the gray matter differences between sexes is small or nonexistent. Thus, the percentage of gray matter appears to be more related to brain size than it is to gender.[45][46]
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);[43] and 33% more synapses per mm3 of cerebral cortex.[47] Another difference is that females generally have faster blood flow to their brains and lose less brain tissue as they age than males do.[48] Additionally, depression and chronic anxiety are much more common in women than in men, and it has been speculated, by some, that this is due to differences in the brain's serotonin system).[49]
Genetic and hormonal causes
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 sexes was observed in the transcription of the PCDH11X/Y gene pair, a pair unique to Homo sapiens.[50] It has been argued[by whom?] that the Y chromosome is primarily responsible for males being more susceptible to mental illnesses.
Hormones significantly affect human brain formation, as well as brain development at puberty. A 2004 review in Nature Reviews Neuroscience observed that "because it is easier to manipulate hormone levels than the expression of sex chromosome genes, the effects of hormones have been studied much more extensively, and are much better understood, than the direct actions in the brain of sex chromosome genes." It concluded that while "the differentiating effects of gonadal secretions seem to be dominant," the existing body of research "support the idea that sex differences in neural expression of X and Y genes significantly contribute to sex differences in brain functions and disease."[51]
Sensory systems
- Females have a more sensitive sense of smell than males, both in the differentiation of odors, and in the detection of slight or faint odors.[52]
- There is also indication that females are better at discerning differences in colours, while males are more aware of, and capable of discerning movement.[citation needed]
- Females have more pain receptors in the skin. That may contribute to the lower pain tolerance of women.[53]
- Males have stronger spatial analysis capabilities, in both navigation[54] and awareness.[55]
Tissues and hormones
- Women generally have a higher body fat percentage than men.[1]
- Women usually have lower blood pressure than men, and women's hearts beat faster, even when they are asleep.[56]
- Men generally have more muscle tissue mass, particularly in the upper body.[citation needed]
- Men and women have different levels of certain hormones. Men have a higher concentration of androgens while women have a higher concentration of estrogens. The main male-associated hormone is testosterone.
- Adult men have approximately 5.2 million red blood cells per cubic millimeter of blood, whereas women have approximately 4.6 million.[57]
- Females typically have more white blood cells (stored and circulating), more granulocytes and B and T lymphocytes. Additionally, they produce more antibodies at a faster rate than males. Hence they develop fewer infectious diseases and succumb for shorter periods.[13]
- Males dissipate heat faster than females through their sweat glands.[citation needed] Females have a greater insulation and energy reserves stored in subcutaneous fat, absorbing exothermic heat less and retaining endothermic heat to a greater degree.[citation needed]
Health
Life span
Females live longer than males in most countries around the world. One possible explanation is the generally more risky behavior engaged in by males. More males than females die young because of war, criminal activity, and accidents. However, the gap between males and females is decreasing in many developed countries as more women take up unhealthy practices that were once considered masculine like smoking and drinking alcohol,[58] and more men practice healthier living. In Russia, however, the sex-associated gap has been increasing as male life expectancy declines.[59]
Health issues
Chromosome linked
Certain diseases and conditions are clearly sex related in that they are caused by the chromosomes that regulate sex differentiation. Some conditions are X-linked recessive, in that the gene is carried on the X chromosome. Genetic females (XX) will show symptoms of the disease only if both their X chromosomes are defective with a similar deficiency, whereas genetic males (XY) will show symptoms of the disease if their only X chromosome is defective. (A woman may carry such a disease on one X chromosome but not show symptoms if the other X chromosome works sufficiently.) For this reason, such conditions are far more common in males than in females. Examples of X-linked recessive conditions are color blindness, hemophilia, and Duchenne muscular dystrophy.
No vital genes reside only on the Y chromosome, since roughly half of humans (females) do not have Y chromosomes. Still there are diseases that are caused by a defective y-chromosome or of a defective number of them. One human disease linked to a defect on the Y chromosome is defective testicular development. Other conditions include Klinefelter's syndrome and XX male syndrome.
General health differences
The World Health Organization (WHO) has produced a number of reports on gender and health.[60] The following trends are shown:
- Overall rates of mental illness are similar for men and women. There is no significant gender difference in rates of schizophrenia and bipolar depression. Women are more likely to suffer from unipolar depression, anxiety, eating disorders, and post-traumatic stress disorder. Men are more likely to suffer from alcoholism and antisocial personality disorder.
- Worldwide, more men than women are infected with HIV. The exception is sub-Saharan Africa, where more women than men are infected.
- Adult males are more likely to be diagnosed with tuberculosis.
- Before menopause, women are less likely to suffer from cardiovascular disease. However, after age 60, the risk for both men and women is the same.
- Overall, men are more likely to suffer from cancer, with much of this driven by lung cancer. In most countries, more men than women smoke, although this gap is narrowing especially among young women.
- Women are twice as likely to be blind as men. In developed countries, this may be linked to higher life expectancy and age-related conditions. In developing countries, women are less likely to get timely treatments for conditions that lead to blindness such as cataracts and trachoma.
- Women are more likely to suffer from osteoarthritis and osteoporosis.
Some other sex related health differences include:
- Anterior cruciate ligament injuries, especially in basketball, occur more often in women than in men.
- From conception to death, but particularly before adulthood, females are generelly less vulnerable than males to developmental difficulties and chronic illnesses.[61][62] This could be due to females having two x chromosomes instead of just one,[63] or in the reduced exposure to testosterone.[64]
See also
- Gender-based medicine
- Genetics of gender
- Sexual dimorphism
- Sex differentiation
- Sex and intelligence
- Virilization
- List of homologues of the human reproductive system
References
Notes
- ^ a b Gustafsson A & Lindenfors P (2004). "Human size evolution: no allometric relationship between male and female stature". Journal of Human Evolution. 47 (4): 253–266. doi:10.1016/j.jhevol.2004.07.004. PMID 15454336.
- ^ Gray 1918, Nowell 1926, Green 2000, et al.
- ^ a b Ogden et al (2004). Mean Body Weight, Height,and Body Mass Index, United States 1960–2002 Advance Data from Vital and Health Statistics, Number 347, October 27, 2004.
- ^ Gender Differences in Endurance Performance and Training
- ^ http://www.ncbi.nlm.nih.gov/pubmed/8477683
- ^ Frontera, Hughes, Lutz & Evans (1991). A cross-sectional study of muscle strength and mass in 45- to 78-yr-old men and women. J Appl Physiol.;71(2):644-50.
- ^ R J Maughan, J S Watson and J Weir(1983). Strength and cross-sectional area of human skeletal muscle. The Journal of Physiology, 338, 37-49.
- ^ Churchchill, AJG; Manning, JT; Peters, M. (2007). "The effects of sex, ethnicity, and sexual orientation on self-measured digit ratio (2D:4D)". Archives of Sexual Behavior. 36 (2): 251–260. doi:10.1007/s10508-006-9166-8. PMID 17394056.
- ^ http://wiki.answers.com/Q/Why_do_men_have_Adam's_apples
- ^ Merry (2005), p 48
- ^ Thieme Atlas of Anatomy (2006), p 112
- ^ Number of Ribs
- ^ a b Glucksman, A. (1981) Sexual Dimorphism in Human and Mammalian Biology and Pathology (Academic Press, 1981), pp. 66-75
- ^ Gender-related features of skin Procter & Gamble Haircare Research Centre 1997
- ^ Male Pattern Baldness
- ^ a b c Frost, P. (2007). Sex linkage of human skin, hair, and eye color
- ^ Frost, P. (1988). Human skin color: A possible relationship between its sexual dimorphism and its social perception. Perspectives in Biology and Medicine, 32, 38–58.
- ^ Frost, P. (2006). "European hair and eye color - A case of frequency-dependent sexual selection?". Evolution and Human Behavior. 27: 85–103. doi:10.1016/j.evolhumbehav.2005.07.002.
- ^ Duffy DL, Montgomery GW, Chen W; et al. (2007). "A three-single-nucleotide polymorphism haplotype in intron 1 of OCA2 explains most human eye-color variation". Am. J. Hum. Genet. 80 (2): 241–52. doi:10.1086/510885. PMC 1785344. PMID 17236130.
{{cite journal}}
: Explicit use of et al. in:|author=
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ignored (help)CS1 maint: multiple names: authors list (link) - ^ Patrick, S. et. al (2007). Genetic determinants of hair, eye and skin pigmentation in Europeans. Nature Genetics Published online: 21 October 2007 doi:10.1038/ng.2007.13
- ^ http://onlinelibrary.wiley.com/doi/10.1111/j.1469-1809.2009.00504.x/abstract
- ^ Interaction between loci affecting human pigmentation in Poland
- ^ MedlinePlus Encyclopedia: Semen analysis
- ^ Graph @ FertilityLifelines.
- ^ Graph @ Epigee.org.
- ^ Age and Fertility: A Guide for Patients, American Society for Reproductive Medicine, 2003.
- ^ Montgomery SM, Lambe M, Olsson T, Ekbom A (2004). "Parental age, family size, and risk of multiple sclerosis". Epidemiology. 15 (6): 717–23. doi:10.1097/01.ede.0000142138.46167.69. PMID 15475721.
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ignored (help)CS1 maint: multiple names: authors list (link) - ^ Reichenberg A, Gross R, Weiser M; et al. (2006). "Advancing paternal age and autism". Arch. Gen. Psychiatry. 63 (9): 1026–32. doi:10.1001/archpsyc.63.9.1026. PMID 16953005.
{{cite journal}}
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ignored (help)CS1 maint: multiple names: authors list (link) - ^ Choi JY, Lee KM, Park SK; et al. (2005). "Association of paternal age at birth and the risk of breast cancer in offspring: a case control study". BMC Cancer. 5: 143. doi:10.1186/1471-2407-5-143. PMC 1291359. PMID 16259637.
{{cite journal}}
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(help)CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link) - ^ Sipos A, Rasmussen F, Harrison G; et al. (2004). "Paternal age and schizophrenia: a population based cohort study". BMJ. 329 (7474): 1070. doi:10.1136/bmj.38243.672396.55. PMC 526116. PMID 15501901.
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ignored (help)CS1 maint: multiple names: authors list (link) - ^ Saha S, Barnett AG, Foldi C; et al. (2009). "Advanced paternal age is associated with impaired neurocognitive outcomes during infancy and childhood". PLoS Med. 6 (3): e40. doi:10.1371/journal.pmed.1000040. PMC 2653549. PMID 19278291.
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ignored (help)CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link) - ^ oldest birth parents
- ^ Robert W Goy and Bruce S McEwen. Sexual Differentiation of the Brain: Based on a Work Session of the Neurosciences Research Program. MIT Press Classics. Boston: MIT Press, 1980.
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Ho, K.C.; Roessmann, U.; Straumfjord, J.V.; Monroe, G. (1980). "Analysis of brain weight. I. Adult brain weight in relation to sex, race, and age". Arch. Pathol. Lab. Med. 104 (12): 635–9. PMID 6893659.
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ignored (help)CS1 maint: multiple names: authors list (link) - ^ Frederikse ME, Lu A, Aylward E, Barta P, Pearlson G (1999). "Sex differences in the inferior parietal lobule". Cereb. Cortex. 9 (8): 896–901. doi:10.1093/cercor/9.8.896. PMID 10601007.
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ignored (help)CS1 maint: multiple names: authors list (link) - ^ Harasty J, Double KL, Halliday GM, Kril JJ, McRitchie DA (1997). "Language-associated cortical regions are proportionally larger in the female brain". Arch. Neurol. 54 (2): 171–6. PMID 9041858.
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Haier, R.J.; Jung, R.E.; Yeo, R.A.; et al. (2005). "The neuroanatomy of general intelligence: sex matters". NeuroImage. 25 (1): 320–327. doi:10.1016/j.neuroimage.2004.11.019. PMID 15734366.
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Haier, R.J.; Jung, R.E.; Yeo, R.A.; Head, K.; Alkire, M.T. (2004). "Structural brain variation and general intelligence" (PDF). Neuroimage. 23 (1): 425–33. doi:10.1016/j.neuroimage.2004.04.025. PMID 15325390.
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ignored (help)CS1 maint: multiple names: authors list (link) - ^ "Intelligence in men and women is a gray and white matter: Men and women use different brain areas to achieve similar IQ results, UCI study finds" University of California, Irvine. Press release. January 20, 2005.
- ^ a b Marner L, Nyengaard JR, Tang Y, Pakkenberg B. (2003). Marked loss of myelinated nerve fibers in the human brain with age. J Comp Neurol. 462(2):144-52. PMID 12794739 Cite error: The named reference "Marner" was defined multiple times with different content (see the help page).
- ^ Gur, Ruben C. (1999-05-15). "Sex Differences in Brain Gray and White Matter in Healthy Young Adults: Correlations with Cognitive Performance". The Journal of Neuroscience. 19 (10): 4065–4072. PMID 10234034. Retrieved 2008-05-24.
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suggested) (help) - ^ Leonard, C. M., Towler, S., Welcome, S., Halderman, L. L., Otto, R. Eckert, M. A., & Chiarello, C. (2008) Size matters: Cerebral volume influences sex differences in neuroanatomy. Cerebral Cortex, 18(12), 2920-2931.
- ^ Luders, E., Steinmetz, H., & Jancke, L. (2002). Brain size and grey matter volume in the healthy human brain. NeuroReport, 13(17), 2371-2374.
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- ^ Marano, Hara Estroff (2003). "The New Sex Scorecard". Psychology Today.
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ignored (help) - ^ Sex differences in the brain's serotonin system
- ^ Alexandra M. Lopes and others,'Inactivation status of PCDH11X: sexual dimorphisms in gene expression levels in brain', Human Genetics 119 (2006): 1–9.
- ^ Arnold, A. P. Sex chromosomes and brain gender. Nature Rev. Neurosci. 5, 701-708 (2004)
- ^ "Women nose ahead in smell tests". BBC News. 2002-02-04. Retrieved 2010-05-23.
- ^ http://www.sciencedaily.com/releases/2005/10/051025073319.htm
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- ^ Bren, Linda (2005). "Does Sex Make a Difference?". FDA Consumer magazine.
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ignored (help) - ^ Howstuffworks "Red Blood Cells"
- ^ Lifestyle 'hits life length gap' BBC September 16, 2005
- ^ A Country of Widows Viktor Perevedentsev, New Times, May 2006
- ^ Gender, women, and health Reports from WHO 2002–2005
- ^ Neurologic and Developmental Disability at Six Years of Age after Extremely Preterm Birth / Neil Marlow et al. / New England Journal of Medicine 352 #1 (2005)
- ^ The Fragile Male / Sebastien Kraemer / British Medical Journal 321 (2000)
- ^ Pas De Deux of Sexuality is Written in the Genes / Nicholas Wade / New York Times, 10 April 2007
- ^ Men: Evolutionary and Life History / Richard Bribiescas (2008) ISBN 0-674-03034-6
Sources
- Merry, Clare V. (2005). "Pelvic Shape". Mind - Primary Cause of Human Evolution. Trafford Publishing. ISBN 1412054575.
- Thieme Atlas of Anatomy: General Anatomy and Musculoskeletal System. Thieme. 2006. ISBN 1-58890-419-9.
Further reading
- Geary DC (2006). "Sex differences in social behavior and cognition: utility of sexual selection for hypothesis generation". Horm Behav. 49 (3): 273–5. doi:10.1016/j.yhbeh.2005.07.014. PMID 16137691.
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External links
- Brin, David (1996). "Neoteny and Two-Way Sexual Selection in Human Evolution: A Paleo-Anthropological Speculation on the Origins of Secondary-Sexual Traits, Male Nurturing and the Child as a Sexual Image". Journal of Social and Evolutionary Systems. 18: 257–76. doi:10.1016/1061-7361(95)90006-3.: .