Sexual intercourse

From Wikipedia, the free encyclopedia
Jump to: navigation, search
This article is primarily about sexual intercourse among humans. For sexual intercourse among other animals, see Animal sexual behaviour.
Sexual intercourse in the missionary position, the most common human sex position,[1][2] depicted by Édouard-Henri Avril

Sexual intercourse, or coitus or copulation, is principally the insertion and thrusting of a male's penis, usually when erect, into a female's vagina for the purposes of sexual pleasure or reproduction.[3] This is also known as vaginal intercourse or vaginal sex.[2][4] Other forms of penetrative sexual intercourse include penetration of the anus by the penis (anal sex), penetration of the mouth by the penis or oral penetration of the female genitalia (oral sex), sexual penetration by the fingers (fingering), and penetration by use of a strap-on dildo.[5][6][7] These activities involve physical intimacy between two or more individuals and are usually used among humans solely for physical or emotional pleasure and commonly contribute to human bonding.[5][8]

A variety of views concern what constitutes sexual intercourse or other sexual activity,[9][10] which can also impact views on sexual health.[11] Although the term sexual intercourse, particularly the variant coitus, generally denotes penile-vaginal penetration and the possibility of creating offspring (which is the fertilization process known as reproduction),[3] it also commonly denotes penetrative oral sex and particularly penile-anal sex.[12] Non-penetrative sex acts, such as non-penetrative forms of cunnilingus or mutual masturbation, have been termed outercourse,[13] but may additionally be among the sexual acts contributing to human bonding and considered sexual intercourse.[5][14] The term sex, often a shorthand for sexual intercourse, can mean any form of sexual activity.[15][16] Because people can be at risk of contracting sexually transmitted infections during these activities,[11][17] though the transmission risk is significantly reduced during non-penetrative sex,[18][19] safe sex practices are advised.[11]

Various jurisdictions have placed restrictive laws against certain sexual acts, such as incest, sexual activity with minors, extramarital sex, prostitution, sodomy, rape and zoophilia. Religious beliefs also play a role in personal decisions about sexual intercourse or other sexual activity, such as decisions about virginity,[10][20] or legal and public policy matters. Religious views on sexuality vary significantly between different religions and sects of the same religion, though there are common themes, such as prohibition of adultery.

Reproductive sexual intercourse between non-human animals is more often termed copulation, and sperm may be introduced into the female's reproductive tract in non-vaginal ways among the animals, such as by cloacal copulation. For most non-human mammals, mating and copulation occur at the point of estrus (the most fertile period of time in the female's reproductive cycle), which increases the chances of successful impregnation.[21][22] However, bonobos, dolphins and chimpanzees are known to engage in sexual intercourse regardless of whether or not the female is in estrus, and to engage in sex acts with same-sex partners.[23] Like humans engaging in sexual activity primarily for pleasure,[8] this behavior in the aforementioned animals is also presumed to be for pleasure,[24] and a contributing factor to strengthening their social bonds.[8]

Behaviors

Definitions

19th-century painting of a couple engaged in vaginal intercourse, by Achille Devéria
19th-century erotic interpretation of Hadrian and Antinous engaged in anal intercourse, by Édouard-Henri Avril

Behaviors termed sexual intercourse may be defined by different words, including coitus, copulation, coition or intercourse (which is typically shorthand for sexual intercourse). The term coitus is derived from the Latin word coitio or coire, meaning "a coming together or joining together" or "to go together"; it describes a variety of sexual activities under ancient Latin terms, but usually refers exclusively to penile-vaginal penetration,[25] which is often termed vaginal intercourse or vaginal sex.[4][26] Vaginal sex, and less often vaginal intercourse, may also refer to any vaginal sexual activity, particularly if penetrative, including vaginal sexual activity between lesbian couples.[27][28] Copulation, by contrast, most often means the mating process of non-human animals; it is generally defined as the sexually reproductive act of transferring sperm from a male to a female or sexual procreation between a man and a woman,[29][30][31] but may also denote any sexual activity between opposite-sex or same-sex pairings.[31]

Although use of the terms sexual intercourse and sex to denote penile-vaginal intercourse are the prevalent usages of the words in common discourse,[32] sex and the phrase "have sex" can mean any penetrative or non-penetrative sexual activity between two or more people.[15][16][33] The World Health Organization (WHO) states that non-English languages and cultures "use different terms for sexual activity, with slightly different meanings".[16] Various vulgar or slang words and euphemisms are also used to describe sexual intercourse or other sexual activity, such as the term fuck and the phrase "sleep together".[34][35] Penetration of the vagina by the erect penis is additionally known as intromission, or by the Latin name immissio penis (Latin for "insertion of the penis").[36]

Commonly, researchers define sexual intercourse as penile-vaginal intercourse while using specific terms, such as anal sex or oral sex, for other sexual activities.[37] Scholars Richard M. Lerner and Laurence Steinberg state that researchers also "rarely disclose how they define sex or even whether they resolved potential discrepancies in definitions of sex".[9] Learner and Steinberg attribute researchers' focus on penile-vaginal sex to "the larger culture's preoccupation with this form of sexual activity," and have expressed concern that the "widespread, unquestioned equation of penile-vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question [about sexual activity] matches what the researcher had in mind'".[9] This focus also relegates other forms of mutual sexual activity to foreplay or regards them as not being "real sex" and additionally limits how rape is defined.[38][39][40][41] There is also concern among scholars that conceptually conflating sexual activity with vaginal intercourse and sexual function hinders and limits information about sexual behavior that non-heterosexual people may be engaging in, or information about heterosexuals who may be engaging in non-vaginal sexual activity.[39]

Vaginal, anal and oral sex, especially their penetrative forms, are the sexual activities most commonly recognized as sexual intercourse.[42] Though non-penetrative and non-penile-vaginal sexual activities may be regarded as sexual intercourse,[5][6][14] they may also be regarded as maintaining "technical virginity" or as "outercourse," regardless of any penetrative aspects; this is more often the case for oral sex than for anal sex.[43] Virginity loss is often based on penile-vaginal intercourse partly because heterosexual couples may engage in anal or oral sex not only for sexual pleasure, but as ways of maintaining that they are virgins if they have not engaged in the reproductive act of coitus.[43] Similarly, gay men may consider frotting or oral sex as ways of maintaining their virginities, with penile-anal penetration defined as sexual intercourse and resulting in virginity loss, while other gay men may define frotting or oral sex as their main forms of sexual intercourse.[10][44][45] Lesbians may define oral sex or fingering as sexual intercourse and resulting in virginity loss,[9][10][46] and may also regard tribadism as a primary form of sexual activity.[2][47]

Studies regarding the definition of sexual intercourse sometimes conflict. A 1999 study by the Kinsey Institute examined the definition of sex based on a 1991 random sample of 599 college students from 29 U.S. states; it reported that while "virtually every college student they surveyed considered penile-vaginal intercourse to be sex," and 19–20% said that anal intercourse was not sex, 60% said oral-genital contact (fellatio, cunnilingus) did not constitute having sex.[33][48][49] Similarly, a 2003 study published in the Canadian Journal of Human Sexuality focusing on definitions of having sex and noting studies concerning university students from the United States, the United Kingdom, and Australia reported that "[w]hile the vast majority of respondents (more than 97%) in these three studies included penile-vaginal intercourse in their definition of sex, fewer (between 70% and 90%) respondents considered penile-anal intercourse to constitute having sex" and that "oral-genital behaviours were defined as sex by between 32% and 58% of respondents".[15] The Centers for Disease Control and Prevention (CDC) stated in 2009 that "[a]lthough there are only limited national data about how often adolescents engage in oral sex, some data suggest that many adolescents who engage in oral sex do not consider it to be 'sex'; therefore they may use oral sex as an option to experience sex while still, in their minds, remaining abstinent".[50]

The specificity of questions concerning sexual activity can additionally affect definitions of sexual intercourse or other sexual behaviors. Another study by the Kinsey Institute sampled 484 people, ranging in ages 18–96. The study reported that nearly 95% of its participants "agreed that penile-vaginal intercourse meant 'had sex.' But the numbers changed as the questions got more specific". 11% of respondents based "had sex" on whether the man had achieved an orgasm, concluding that absence of an orgasm does not constitute "having had" sex; "[a]bout 80 percent of respondents said penile-anal intercourse meant 'had sex.' About 70 percent of people believed oral sex was sex."[33] Condom use is also a factor, with some men stating that sexual activity involving the protection of a condom is not "real sex" or "the real thing".[33][51][52] One study reported that older generations of men (65 or older) in particular do not view sexual activity involving the protection of a condom to be sex.[33] This view is common among men in Africa,[51][52] where sexual activity involving the protection of a condom is often associated with emasculation because condoms prevent direct penile–to–skin genital contact.[51]

Bonding and stimulus variation

Copulation ranges from a purely reproductive activity to one of emotional bonding. For example, sexual intercourse and sexual activity in general often play a strong role in human bonding.[8] In many societies, it is normal for couples to have sexual intercourse while using some method of birth control (contraception), sharing pleasure and strengthening their emotional bond through sexual activity even though they are deliberately avoiding pregnancy.[8]

In humans and bonobos, the female undergoes relatively concealed ovulation so that male and female partners commonly do not know whether she is fertile at any given moment. One possible reason for this distinct biological feature may be formation of strong emotional bonds between sexual partners important for social interactions and, in the case of humans, long-term partnership rather than immediate sexual reproduction.[8][53] For humans in particular, cooperative behavior in a community and, by extension, sexual activity reinforce social bonds between individuals and may form larger social structures. The resulting cooperation encourages collective tasks that promote the survival of each member of the group.[23]

Édouard-Henri Avril depiction of a woman on top position, a position that is more likely to stimulate the clitoris[1]

Sexual intercourse or other sexual activity can encompass various sexually stimulating factors (physical stimulation or psychological stimulation), including different sex positions or the use of sex toys.[2][6][54] Foreplay may precede particular sexual activities, often leading to sexual arousal of the partners and resulting in the erection of the penis or natural lubrication of the vagina.[55] It is also common for people to be as sexually satisfied by being kissed, touched erotically, or held as they are by sexual intercourse.[56]

During coitus, the partners move their hips to move the penis backward and forward inside the vagina to cause friction, typically without fully removing the penis. In this way, they stimulate themselves and each other, often continuing until orgasm in either or both partners is achieved.[14][57]

For human females, stimulation of the clitoris plays a significant role in sexual activity; 70–80% of women require direct clitoral stimulation to achieve orgasm,[58][59][60] though indirect clitoral stimulation (for example, via vaginal intercourse) may also be sufficient (see orgasm in females).[61][62] Because of this, some couples may engage in the woman on top position or the coital alignment technique, a technique combining the "riding high" variation of the missionary position with pressure-counterpressure movements performed by each partner in rhythm with sexual penetration, to maximize clitoral stimulation.[1][6][63]

Édouard-Henri Avril depiction of cunnilingus in the life of Sappho

Anal sex involves stimulation of the anus, anal cavity, sphincter valve or rectum; it most commonly means the insertion of a man's penis into another person's rectum, but may also mean pegging, the use of other sex toys or fingers to penetrate the anus, or anilingus.[64]

Oral sex consists of all the sexual activities that involve the use of the mouth and throat to stimulate genitalia or anus. It is sometimes performed to the exclusion of all other forms of sexual activity, and may include the ingestion or absorption of semen or vaginal fluids.[2][65]

Fingering (or digital penetration or digital intercourse) involves the manual manipulation of the clitoris, rest of the vulva, vagina or anus for the purpose of sexual arousal and sexual stimulation; it may constitute the entire sexual encounter or it may be part of mutual masturbation, foreplay or other sexual activities.[28][66][67]

Reproduction

Sexual intercourse is perhaps 385 million years old, and it is likely that the oldest jawed fish on Earth was the first animal to reproduce by copulation.[68] Reproduction among humans usually occurs with penile-vaginal penetration.[69] Male orgasm usually includes ejaculation, a series of muscular contractions that deliver semen containing male gametes known as sperm cells or spermatozoa from the penis into the vagina. The subsequent route of the sperm from the vault of the vagina is through the cervix and into the uterus, and then into the fallopian tubes. Millions of sperm are present in each ejaculation, to increase the chances of one fertilizing an egg or ovum (see sperm competition). When a fertile ovum from the female is present in the fallopian tubes, the male gamete joins with the ovum, resulting in fertilization and the formation of a new embryo. When a fertilized ovum reaches the uterus, it becomes implanted in the lining of the uterus (the endometrium) and a pregnancy begins.[69] Unlike most species, human sexual activity is not linked to periods of estrus and can take place at any time during the reproductive cycle, even during pregnancy.[53][70]

When a sperm donor has sexual intercourse with a woman who is not his partner and for the sole purpose of impregnating the woman, this may be known as natural insemination, as opposed to artificial insemination. Artificial insemination is a form of assisted reproductive technology, which are methods used to achieve pregnancy by artificial or partially artificial means.[71] For artificial insemination, sperm donors may donate their sperm through a sperm bank, and the insemination is performed with the express intention of attempting to impregnate the female; to this extent, its purpose is the medical equivalent of sexual intercourse.[72][73]

Reproductive methods also extend to gay and lesbian couples. For gay male pairings, there is the option of surrogate pregnancy; for lesbian couples, there is donor insemination in addition to choosing surrogate pregnancy.[74][75] Surrogacy and donor insemination remain the primary methods. Surrogacy is an arrangement in which a woman carries and delivers a child for another couple or person. The woman may be the child's genetic mother (traditional surrogacy) or she may carry a pregnancy to delivery after having another woman's eggs transferred to her uterus (gestational surrogacy). Gay or lesbian pairings who want the host to have no genetic connection to the child may choose gestational surrogacy and enter into a contract with an egg donor. Gay male couples might decide that they should both contribute semen for an in vitro fertilisation (IVF) process, which further establishes the couple's joint intention to become parents.[75] Lesbian couples often have contracts drafted to extinguish the legal rights of the sperm donor, while creating legal rights for the parent who is not biologically related to the child.[76]

Safe sex and contraception

There are a variety of safe sex methods that are practiced by heterosexual and same-sex couples, including non-penetrative sex acts,[19][77] and heterosexual couples may use oral or anal sex (or both) as a means of birth control (contraception).[78][79] However, pregnancy can still occur with anal sex or other forms of sexual activity if the penis is near the vagina (such as during intercrural sex or other genital-genital rubbing) and its sperm is deposited near the vagina's entrance and travels along the vagina's lubricating fluids; the risk of pregnancy can also occur without the penis being near the vagina because sperm may be transported to the vaginal opening by the vagina coming in contact with fingers or other non-genital body parts that have come in contact with semen.[80][81]

Safe sex is a relevant harm reduction philosophy,[11][82] and condoms are used as a form of safe sex and contraception. Condoms are widely recommended for the prevention of sexually transmitted infections (STIs).[11][82] According to reports by the National Institutes of Health (NIH) and World Health Organization (WHO), correct and consistent use of latex condoms reduces the risk of HIV/AIDS transmission by approximately 85–99% relative to risk when unprotected.[83][84] The most effective way to avoid sexually transmitted infections is to abstain from sexual intercourse, especially vaginal, anal, and oral sexual intercourse.[82]

Decisions and options concerning birth control can be affected by cultural reasons, such as religion, gender roles or folklore.[18] In the predominantly Catholic countries Ireland, Italy and the Philippines, fertility awareness and the rhythm method are emphasized while disapproval is expressed with regard to other contraceptive methods.[18] Worldwide, sterilization is a more common birth control method,[18] and use of the intrauterine device (IUD) is the most common and effective way of reversing contraception.[18][85] Conception and contraception are additionally a life-and-death situation in developing countries, where one in three women give birth before age 20; however, 90% of unsafe abortions in these countries could be prevented by effective contraception use.[18]

In 2004, the Guttmacher Institute indicated in 2002 that 62% of the 62 million women aged 15–44 are currently using a contraceptive method, that among U.S. women who practice contraception, the birth-control pill is the most popular choice (30.6%), followed by tubal sterilization (27.0%) and the male condom (18.0%), and that 27% of teenage women using contraceptives choose condoms as their primary method.[86] A 2006 Kaiser Family Foundation report stated that among sexually active 15- to 19-year-olds in the U.S., 83% of females and 91% of males reported using at least one method of birth control during last intercourse.[87]

The National Survey of Sexual Health and Behavior (NSSHB) indicated in 2010 that "1 of 4 acts of vaginal intercourse are condom-protected in the U.S. (1 in 3 among singles)," that "condom use is higher among black and Hispanic Americans than among white Americans and those from other racial groups," and that "adults using a condom for intercourse were just as likely to rate the sexual extent positively in terms of arousal, pleasure and orgasm than when having intercourse without one".[88]

Prevalence

Penile-vaginal penetration is the most common form of sexual intercourse.[4][26] Studies indicate that most heterosexual couples engage in vaginal intercourse "almost every time they have sex".[26] The National Survey of Sexual Health and Behavior (NSSHB) reported in 2010 that vaginal intercourse is "the most prevalent sexual behavior among men and women of all ages and ethnicities".[26] In 2013, Clint E. Bruess et al. stated that vaginal sex "is the most frequently studied behavior" and, besides in many cultures being what is usually meant when people refer to "having sex" or "sexual intercourse," is "often the focus of sexuality education programming for youth."[89]

Regarding oral or anal intercourse, the CDC stated in 2009, "Studies indicate that oral sex is commonly practiced by sexually active male-female and same-gender couples of various ages, including adolescents."[50] The 2010 NSSHB study reported that vaginal intercourse was practiced more than insertive anal intercourse among men, but that 13% to 15% of men aged 25 to 49 practiced insertive anal intercourse. Receptive anal intercourse was infrequent among men, with approximately 7% of men aged 14 to 94 years old having said that they were a receptive partner during anal intercourse. It said that women engage in anal intercourse less commonly than men, but that the practice is not uncommon among women; it was estimated that 10% to 14% of women aged 18 to 39 years old practiced anal sex in the past 90 days, and that most of the women said they practiced it once a month or a few times a year.[26]

The prevalence of sexual intercourse has been compared cross-culturally. In 2003, Michael Bozon of the French Institut national d'études démographiques conducted a cross-cultural study titled "At what age do women and men have their first sexual intercourse?." In the first group of the contemporary cultures he studied, which included sub-Saharan Africa (listing Mali, Senegal and Ethiopia), the data indicated that the age of men at sexual initiation in these societies is at later ages than that of women, but is often extra-marital; the study considered the Indian subcontinent to also fall into this group, though data was only available from Nepal.[90][91]

In the second group, the data indicated families encouraged daughters to delay marriage, and to abstain from sexual activity before that time. However, sons are encouraged to gain experience with older women or prostitutes before marriage. Age of men at sexual initiation in these societies is at lower ages than that of women; this group includes Latin cultures, both from southern Europe (Portugal, Greece and Romania are noted) and from Latin America (Brazil, Chile, and the Dominican Republic). The study considered many Asian societies to also fall into this group, although matching data was only available from Thailand.[90][91]

In the third group, age of men and women at sexual initiation was more closely matched; there were two sub-groups, however. In non-Latin, Catholic countries (Poland and Lithuania are mentioned), age at sexual initiation was higher, suggesting later marriage and reciprocal valuing of male and female virginity. The same pattern of late marriage and reciprocal valuing of virginity was reflected in Singapore and Sri Lanka. The study considered China and Vietnam to also fall into this group, though data were not available.[90][91] In northern and eastern European countries, age at sexual initiation was lower, with both men and women involved in sexual intercourse before any union formation; the study listed Switzerland, Germany and the Czech Republic as members of this group.[90][91]

Concerning United States data, national surveys in 1995 indicated that at least 3/4 of all men and women in the U.S. engaged in sexual intercourse by their late teenage years, and more than 2/3 of all sexually experienced teens had two or more partners.[92] Based on the 2002 National Survey of Family Growth, published by the U.S. Department of Health and Human Services, the average age of first sexual intercourse in U.S. participants aged 15 to 44 was 17.3 years for females and 17.0 years for males.[93][94][95] Special tabulations by the National Center for Health Statistics suggest that this figure changed between 2006 and 2010 to 17.1 years for both males and females.[96] The Centers for Disease Control and Prevention (CDC) stated that 45.5 percent of girls and 45.7 percent of boys had engaged in sexual activity by 19 in 2002; in 2011, reporting their research from 2006–2010, they stated that 43% of American unmarried teenage girls and 42% of American unmarried teenage boys have ever engaged in sexual intercourse.[97] The CDC also reports that American girls will most likely lose their virginity to a boy who is 1 to 3 years older than they are.[97]

The U.S. Department of Health and Human Services reported in 2002 that teenagers are delaying sexual intercourse and other sexual activity until older ages.[98] Between 1988 and 2002, the percentage of people in the U.S. who had sexual intercourse between the ages of 15 to 19 fell from 60 to 46 percent for never-married males, and from 51 to 46 percent for never-married females.[98] Similarly, a 2006 survey conducted by The Observer suggested that most adolescents in Britain were waiting longer to have sexual intercourse than they were only a few years earlier.[99] For example, it was reported in 2002 that 32% of British teenagers were having sex before the age of 16; in 2006, however, it was only 20%. The average age a British teenager lost his or her virginity was reportedly 17.13 years in 2002, and 17.44 years in 2006 on average for girls and 18.06 for boys. The most notable drop among teens who reported having sex was 14 and 15-year-olds.[99] A 2008 survey conducted by YouGov for Channel 4 suggested that 40% of all 14 to 17-year-olds are sexually active, 74% of sexually active 14 to 17-year-olds have had a sexual experience under the age of consent, and 6% of teens would wait until marriage before having sex.[100]

Health effects

General benefits

In humans, sexual intercourse and sexual activity in general have been reported as having health benefits as varied as increased immunity by increasing the body's production of antibodies and subsequent lower blood pressure,[101][102] and decreased risk of prostate cancer.[101] Sexual intimacy and orgasms increase levels of the hormone oxytocin (also known as "the love hormone"), which can help people bond and build trust.[102][103] A long-term study of 3,500 people between ages 30 and 101 by clinical neuropsychologist David Weeks indicated that "sex helps you look between four and seven years younger", based on impartial ratings of the subjects' photographs. Although no study has proven a causal relationship between sex and longevity, Weeks theorized that the benefits indicated by this study are indirectly related to sex but rather a result of any stress reduction, greater contentment, and improved sleep that sex can promote.[104]

General risks

Sexually transmitted infections (STIs) are bacteria, viruses and parasites, which are passed from person to person during sexual contact, especially penetrative sexual intercourse. Some, in particular HIV and syphilis, can also be passed in other ways, including from mother to child during pregnancy and childbirth, through blood products, and by shared hypodermic needles.[105] Gonococcal or chlamydia infections often produce no symptoms. Untreated chlamydia infection can lead to female infertility and ectopic pregnancy. Human papillomavirus can lead to genital and cervical cancers. Syphilis can result in stillbirths and neonatal deaths. Untreated gonococcal infections result in miscarriages, preterm births and perinatal deaths. Infants born to mothers with untreated gonorrhea or chlamydia can develop neonatal conjunctivitis (a serious eye infection), which can lead to blindness.[105] Hepatitis B can also be transmitted through sexual contact.[106] Globally, there are about 350 million chronic carriers of hepatitis B.[107]

There are 19 million new cases of sexually transmitted infections every year in the U.S.,[108] and, in 2005, the World Health Organization estimated that 448 million people aged 15–49 were being infected a year with curable STIs (such as syphilis, gonorrhea and chlamydia).[105] Some STIs can cause a genital ulcer; even if they do not, they increase the risk of both acquiring and passing on HIV up to ten-fold.[105] HIV is one of the world's leading infectious killers; in 2010, approximately 30 million people were estimated to have died because of it since the beginning of the epidemic. Of the 2.7 million new HIV infections estimated to occur worldwide in 2010, 1.9 million (70%) were in Africa. "The estimated 1.2 million Africans who died of HIV-related illnesses in 2010 comprised 69% of the global total of 1.8 million deaths attributable to the epidemic."[109] It is diagnosed by blood tests, and while no cure has been found, it can be controlled by management through antiretroviral drugs for the disease, and patients can enjoy healthy and productive lives.[110]

In cases where infection is suspected, early medical intervention is highly beneficial in all cases. The CDC stated "[t]he risk of HIV transmission from an infected partner through oral sex is much less than the risk of HIV transmission from anal or vaginal sex," but that "[m]easuring the exact risk of HIV transmission as a result of oral sex is very difficult" and that this is "because most sexually active individuals practice oral sex in addition to other forms of sex, such as vaginal and/or anal sex, when transmission occurs, it is difficult to determine whether or not it occurred as a result of oral sex or other more risky sexual activities". They added that "several co-factors may increase the risk of HIV transmission through oral sex"; this includes ulcers, bleeding gums, genital sores, and the presence of other STIs.[50]

In 2005, the World Health Organization (WH0) estimated that 123 million women become pregnant world-wide each year, and around 87 million of those pregnancies or 70.7% are unintentional. Approximately 46 million pregnancies per year reportedly end in induced abortion.[111] Approximately 6 million U.S. women become pregnant per year. Out of known pregnancies, two-thirds result in live births and roughly 25% in abortions; the remainder end in miscarriage. However, many more women become pregnant and miscarry without even realizing it, instead mistaking the miscarriage for an unusually heavy menstruation.[112] The U.S. teenage pregnancy rate fell by 27 percent between 1990 and 2000, from 116.3 pregnancies per 1,000 girls aged 15–19 to 84.5. This data includes live births, abortions, and fetal losses. Almost 1 million American teenage women, 10% of all women aged 15–19 and 19% of those who report having had intercourse, become pregnant each year.[113] Britain has been stated to have a teenage pregnancy rate similar to America's.[114]

Sexual activity can directly cause death, particularly due to coronary circulation complications, which is sometimes termed coital death, coital sudden death or coital coronary.[14][115][116] However, coital deaths are significantly rare.[115] People, especially those who get little or no physical exercise, have a slightly increased risk of triggering a heart attack or sudden cardiac death when they engage in sexual intercourse or any vigorous physical exercise that is engaged in on a sporadic basis.[116] Increased risk is temporary with incidents occurring within a few hours of the activity. Regular exercise reduces, but does not eliminate, the increased risk.[116] In a study in Switzerland of emergency department admissions for conditions related to sexual intercourse, less than 1% had cardiovascular emergencies, 10% had trauma and 12% had neurological emergencies whereof the most frequent were headaches (in 49% of neurological emergencies), followed by subarachnoid hemorrhage (22%) and transient global amnesia (20%).[117]

Sexual activity increases the expression of a gene transcription factor called ΔFosB (Delta FosB) in the brain's reward center;[118][119][120] consequently excessively frequent engagement in sexual activity on a regular (daily) basis can lead to the overexpression of ΔFosB, inducing an addiction to sexual activity.[118][119][120]

Duration and sexual difficulties

Sexual intercourse, when involving a male participant, often ends when the male has ejaculated, and thus the partner might not have time to reach orgasm.[121] In addition, premature ejaculation (PE) is common, and women often require a substantially longer duration of stimulation with a sexual partner than men do before reaching an orgasm.[55][122][123] Masters and Johnson found that men took approximately 4 minutes to reach orgasm with their partners; women took approximately 10–20 minutes to reach orgasm with their partners, but 4 minutes to reach orgasm when they masturbated.[55] Scholars state "many couples are locked into the idea that orgasms should be achieved only through intercourse [penile-vaginal sex]," that "the word foreplay suggests that any other form of sexual stimulation is merely preparation for the 'main event'" and that "[b]ecause women reach orgasm through intercourse less consistently than men," they are likelier than men to fake an orgasm to satisfy their sexual partners.[55]

Painting of an Indian couple (a prince and lady) prolonging sexual intercourse

In 1991, scholars from the Kinsey Institute stated, "The truth is that the time between penetration and ejaculation varies not only from man to man, but from one time to the next for the same man." They added that the appropriate length for sexual intercourse is the length of time it takes for both partners to be mutually satisfied, emphasizing that Kinsey "found that 75 percent of men ejaculated within two minutes of penetration. But he didn't ask if the men or their partners considered two minutes mutually satisfying" and "more recent research reports slightly longer times for intercourse".[124] A 2008 survey of Canadian and American sex therapists stated that the average time for heterosexual intercourse (coitus) was 7 minutes and that 1 to 2 minutes was too short, 3 to 7 minutes was adequate and 7 to 13 minutes desirable, while 10 to 30 minutes was too long.[26][125]

Anorgasmia is regular difficulty reaching orgasm after ample sexual stimulation, causing personal distress.[126] This is significantly more common in women than in men,[127][128] which has been attributed to the lack of sex education with regard to women's bodies, especially in sex-negative cultures, such as clitoral stimulation usually being key for women to orgasm.[128] The physical structure of coitus favors penile stimulation over clitoral stimulation; the location of the clitoris then usually necessitates manual or oral stimulation in order for the female to achieve orgasm.[55] Approximately 20% of women report difficulties with orgasm,[26] 10% of women have never had an orgasm,[129] and 40% or 40–50% have either complained about sexual dissatisfaction or experienced difficulty becoming sexually aroused at some point in their lives.[130]

Vaginismus is involuntary tensing of the pelvic floor musculature, making coitus, or any form of penetration of the vagina, distressing, painful and sometimes impossible for women. It is a conditioned reflex of the pubococcygeus muscle, and is sometimes referred to as the PC muscle. Vaginismus can be a vicious cycle for women; they expect to experience pain during sexual intercourse, which then causes a muscle spasm, which leads to painful sexual intercourse.[128][131] Treatment of vaginismus often includes both psychological and behavioral techniques, including the use of vaginal dilators.[132] Additionally, the use of Botox as a medical treatment for vaginismus has been tested and administered.[133] Painful or uncomfortable sexual intercourse may also be categorized as dyspareunia.[132]

Approximately 40% of males reportedly suffer from some form of erectile dysfunction (ED) or impotence, at least occasionally.[134] Premature ejaculation has been reported to be more common than erectile dysfunction, although some estimates suggest otherwise.[134][122][123] Due to various definitions of the disorder, estimates for the prevalence of premature ejaculation vary significantly more than for erectile dysfunction.[122][123] For example, the Mayo Clinic states, "Estimates vary, but as many as 1 out of 3 men may be affected by [premature ejaculation] at some time."[135] Further, "Masters and Johnson speculated that premature ejaculation is the most common sexual dysfunction, even though more men seek therapy for erectile difficulties" and that this is because "although an estimated 15 percent to 20 percent of men experience difficulty controlling rapid ejaculation, most do not consider it a problem requiring help, and many women have difficulty expressing their sexual needs".[124] The American Urological Association (AUA) estimates that premature ejaculation could affect 21 percent of men in the United States.[136]

For those whose impotence is caused by medical conditions, prescription drugs such as Viagra, Cialis, and Levitra are available. However, doctors caution against the unnecessary use of these drugs because they are accompanied by serious risks such as increased chance of heart attack.[137] The selective serotonin reuptake inhibitor (SSRI) and antidepressant drug dapoxetine has been used to treat premature ejaculation.[138] In clinical trials, those with PE who took dapoxetine experienced sexual intercourse three to four times longer before orgasm than without the drug.[139] Another ejaculation-related disorder is delayed ejaculation, which can be caused as an unwanted side effect of antidepressant medications such as Fluvoxamine; however, all SSRIs have ejaculation-delaying effects, and Fluvoxamine has the least ejaculation-delaying effects.[140]

Although disability-related pain, including as a result of cancer, and mobility impairment can hamper sexual intercourse, in many cases, the most significant impediments to sexual intercourse for individuals with a disability are psychological.[141][142] In particular, people who have a disability can find sexual intercourse daunting due to issues involving their self-concept as a sexual being, or a partner's discomfort or perceived discomfort.[141][142] Temporary difficulties can arise with alcohol and sex, as alcohol can initially increase interest through disinhibition but decrease capacity with greater intake; however, disinhibition can vary depending on the culture.[143][144]

Social effects

Adults

Some researchers, such as Alex Comfort, posit three potential advantages or social effects of sexual intercourse in humans, which are not mutually exclusive; these are reproductive, relational, and recreational.[8][145] While the development of the birth-control pill and other highly effective forms of contraception in the mid to late 20th century increased people's ability to segregate these three functions, they still significantly overlap and in complex patterns. For example: A fertile couple may have sexual intercourse while contracepting not only to experience sexual pleasure (recreational), but also as a means of emotional intimacy (relational), thus deepening their bonding, making their relationship more stable and more capable of sustaining children in the future (deferred reproductive). This couple may emphasize different aspects of sexual intercourse on different occasions, being playful during one episode of sexual intercourse (recreational), experiencing deep emotional connection on another occasion (relational), and later, after discontinuing contraception, seeking to achieve pregnancy (reproductive, or more likely reproductive and relational).[145]

Sexual dissatisfaction due to the lack of sexual intercourse is associated with increased risk of divorce and relationship dissolution, especially for men.[146][147][148] Some research, however, indicates that general dissatisfaction with marriage for men results if their wives flirted with, erotically kissed or became romantically or sexually involved with another man (infidelity),[146][147] and that this is especially the case for men with a lower emotional and composite marital satisfaction.[148] Other studies report that the lack of sexual intercourse does not significantly result in divorce, though it is commonly one of the various contributors to it.[149][150] According to the 2010 National Survey of Sexual Health and Behavior (NSSHB), men whose most recent sexual encounter was with a relationship partner reported greater arousal, greater pleasure, fewer problems with erectile function, orgasm, and less pain during the event than men whose last sexual encounter was with a non-relationship partner.[151]

For women, there is often a complaint about the lack of their spouses' sexual spontaneity. Decreased sexual activity among these women may be the result of their perceived failure to maintain ideal physical attractiveness or because their sexual partners' health issues have hindered sexual intercourse.[152] Some women express that their most satisfying sexual experiences entail being connected to someone, rather than solely basing satisfaction on orgasm.[121][153] With regard to divorce, women are more likely to divorce their spouses for a one-night stand or various infidelities if they are in less cooperative or high-conflict marriages.[148]

Research additionally indicates that non-married couples who are cohabiting engage in sexual intercourse more often than married couples, and are more likely to participate in sexual activity outside of their sexual relationships; this may be due to the "honeymoon" effect (the newness or novelty of sexual intercourse with the partner), since sexual intercourse is usually practiced less the longer a couple is married, with couples engaging in sexual intercourse or other sexual activity once or twice a week, or approximately six to seven times a month.[154] Sexuality in older age also affects the frequency of sexual intercourse, as older people generally engage in sexual intercourse less frequently than younger people do.[154]

Adolescents

Regarding adolescent sexuality, sexual intercourse is usually for relational and recreational purposes as well. However, teenage pregnancy is often disparaged, and research suggests that the earlier onset of puberty for children puts pressure on children and teenagers to act like adults before they are emotionally or cognitively ready.[155] Some studies have concluded that engaging in sexual intercourse leaves adolescents, especially girls, with higher levels of stress and depression, and that girls may be likelier to engage in sexual risk (such as sexual intercourse without the use of a condom),[156][157] but it may be that further research is needed in these areas.[157] In some countries, such as the United States, sex education and abstinence-only sex education curricula are available to educate adolescents about sexual activity; these programs are controversial, as debate exists as to whether or not teaching children and adolescents about sexual intercourse or other sexual activity should only be left up to parents or other caregivers.[158]

One group of Canadian researchers found a relationship between self-esteem and sexual activity. They found that students, especially girls, who were verbally abused by teachers or rejected by their peers were more likely than other students to engage in sex by the end of Grade 7. The researchers speculate that low self-esteem increases the likelihood of sexual activity: "low self-esteem seemed to explain the link between peer rejection and early sex. Girls with a poor self-image may see sex as a way to become 'popular', according to the researchers".[159]

In India, there is evidence that adolescents are becoming more sexually active outside of marriage, which is feared to lead to an increase in the spread of HIV/AIDS among adolescents, as well as the number of unwanted pregnancies and abortions, and add to the conflict between contemporary social values. In India, adolescents have relatively poor access to health care and education, and with cultural norms opposing extramarital sexual behavior, "these implications may acquire threatening dimensions for the society and the nation".[160]

Positive views on adolescent sexual intercourse and other sexual behavior among adolescents have also been expressed. Psychiatrist Lynn Ponton writes, "All adolescents have sex lives, whether they are sexually active with others, with themselves, or seemingly not at all," and that viewing adolescent sexuality as a potentially positive experience, rather than as something inherently dangerous, may help young people develop healthier patterns and make more positive choices regarding sexual activity.[155] Similarly, researchers state that long-term romantic relationships allow adolescents to gain the skills necessary for high-quality relationships later in life[161] and develop feelings of self-worth. Overall, positive romantic relationships among adolescents can result in long-term benefits. High-quality romantic relationships are associated with higher commitment in early adulthood[162] and are positively associated with self-esteem, self-confidence, and social competence.[163][164]

Ethical, religious, and legal views

Erotic painting on ancient Greek kylix

While sexual intercourse, as coitus, is the natural mode of reproduction for the human species, humans have intricate moral and ethical guidelines which regulate the practice of sexual intercourse and vary according to religious and governmental laws. Some governments and religions also have strict designations of "appropriate" and "inappropriate" sexual behavior, which include restrictions on the types of sex acts which are permissible. A historically prohibited or regulated sex act is anal sex.[165][166]

Consent and sexual offenses

Sexual intercourse with a person against their will, or without their informed legal consent, is rape, but may also be termed sexual assault; it is considered a serious crime in most countries.[167][168] More than 90% of rape victims are female, 99% of rapists male, and only about 5% of rapists are strangers to the victims.[168]

Most developed countries have age of consent laws specifying the minimum legal age a person may engage in sexual intercourse with substantially older persons, usually set at about 16–18, while the legal age of consent ranges from 12–20 years of age or is not a matter of law in other countries.[169] Sex with a person under the age of consent, regardless of their stated consent, is often considered to be sexual assault or statutory rape depending on differences in ages of the participants. Some countries treat any sex with a person of diminished or insufficient mental capacity to give consent, regardless of age, as rape.[170]

Max Slevogt depiction of rape

Scholars state that "[p]rior to the 1970s, rape definitions of sex often included only penile-vaginal sexual intercourse"[171] and that if "sex means penile-vaginal intercourse, then rape means forced penile-vaginal intercourse, and other sexual behaviors – such as fondling a person's genitals without her or his consent, forced oral sex, and same-sex coercion – are not considered rape"; they state that "[a]lthough some other forms of forced sexual contact are included within the legal category of sodomy (e.g., anal penetration and oral-genital contact), many unwanted sexual contacts have no legal grounding as rape in some states".[41]

While Robert Francoeur et al. state that there is a broad "conceptualization of sex, including many kinds of sexual penetration (e.g., penile-vaginal intercourse, fellatio, cunnilingus, anal intercourse, or penetration of the genitals or rectum by an object)" for most definitions of rape,[171] scholar Ken Plumber argues that "the legal definition of rape in most countries is unlawful sexual intercourse which means the penis must penetrate the vagina" and that "[o]ther forms of sexual violence towards women such as forced oral sex or anal intercourse, or the insertion of other objects into the vagina, constitute the 'less serious' crime of sexual assault".[38]

Another sexual matter concerning consent is zoophilia, a paraphilia involving sexual activity between human and non-human animals, or a fixation on such practice.[172][173][174] Human sexual activity with non-human animals is not outlawed in some jurisdictions, but it is illegal in others under animal abuse laws or laws dealing with crimes against nature.[175]

Romantic relationships

Sexual orientation and gender

There are various legal positions regarding the definition and legality of sexual intercourse between persons of the same sex or gender. For example, in the 2003 New Hampshire Supreme Court case Blanchflower v. Blanchflower, it was held that female same-sex sexual relations, and same-sex sexual practices in general, did not constitute sexual intercourse, based on a 1961 definition from Webster's Third New International Dictionary that defines sexual intercourse as coitus; and thereby an accused wife in a divorce case was found not guilty of adultery.[176][177] Some countries, such as Islamic countries, consider same-sex sexual behavior an offense punishable by imprisonment or execution.[178]

Marriage and relationships

Sexual intercourse has traditionally been considered an essential part of a marriage; many religious customs required consummation of the marriage by sexual intercourse, and the failure for any reason to consummate the marriage was a ground for annulment, which did not require a divorce process. Annulment declaration implied that the marriage was void from the start; for example, there was no marriage in law. Furthermore, continuing sexual relations between the marriage partners is commonly considered a "marital right" by many religions, permissible to married couples, generally for the purpose of reproduction. There is wide variation with regard to religious or legal opinions about sexual intercourse in marriage. The following are examples:

  • Most denominations of Christianity, including Catholicism, have strict views or rules on what sexual practices are and are not acceptable.[179] Most Christian views on sexual intercourse are formed influenced by various interpretations of the Bible.[180] Sexual intercourse outside of marriage, for example, is considered a sin in some churches; in such cases, sexual intercourse may be referred to as a sacred covenant, holy or as a holy sacrament between husband and wife.[179][180] Historically, Christian teachings often promoted celibacy,[181] although today usually only certain members (for example, certain religious leaders) of some groups take a vow of celibacy, forsaking both marriage and any type of sexual or romantic activity.[180] The Bible may be interpreted as endorsing penile-vaginal penetration as the only form of acceptable sexual activity,[182][183] while other interpretations view the Bible as not being clear on oral sex or other particular sexual behaviors and that it is a personal decision as to whether or not oral sex is acceptable within marriage.[182][184][185] The Bible also prohibits sexual intercourse during menstruation.[185]
  • In The Church of Jesus Christ of Latter-day Saints, or Mormonism, sexual relations within the bonds of matrimony are seen as sacred. Mormons consider sexual relations to be ordained of God for the creation of children and for the expression of love between husband and wife. Members are discouraged from having any sexual relations before marriage, and from being unfaithful to their spouses after marriage.[186]
  • In Judaism, a married Jewish man is required to provide his wife with sexual pleasure called onah (literally, "her time"), which is one of the conditions he takes upon himself as part of the Jewish marriage contract, ketubah, that he gives her during the Jewish wedding ceremony. In Jewish views on marriage, sexual desire is not evil, but must be satisfied in the proper time, place and manner.[187]
  • Islam views sex within marriage as something pleasurable, a spiritual activity, and a duty.[188][189][190] In Shi'ia Islam, men are allowed to enter into an unlimited number of temporary marriages, which are contracted to last for a period of minutes to multiple years and permit sexual intercourse. Shi'ia women are allowed to enter only one marriage at a time, whether temporary or permanent.
  • Wiccans believe that, as declared within the Charge of the Goddess, to "Let my [the Goddess] worship be within the heart that rejoiceth; for behold, all acts of love and pleasure are my rituals." This statement appears to allow one freedom to explore sensuality and pleasure, and mixed with the final maxim within the Wiccan Rede – "26. Eight words the Wiccan Rede fulfill – an' it harm none, do what ye will."[191] – Wiccans are encouraged to be responsible with their sexual encounters, in whatever variety they may occur.[192]
  • Hinduism has varied views about sexuality, but Hindu society, in general, perceives extramarital sex to be immoral and shameful.[188]
  • Buddhist ethics, in its most common formulation, holds that one should neither be attached to nor crave sensual pleasure.
  • In the Bahá'í Faith, sexual relationships are permitted only between a husband and wife.[193]
  • Unitarian Universalists, with an emphasis on strong interpersonal ethics, do not place boundaries on the occurrence of sexual intercourse among consenting adults.[194]
  • According to the Brahma Kumaris and Prajapita Brahma Kumaris religion, the power of lust is the root of all evil and worse than murder.[195] Purity (celibacy) is promoted for peace and to prepare for life in forthcoming Heaven on earth for 2,500 years when children will be created by the power of the mind.[196][197]
  • Shakers believe that sexual intercourse is the root of all sin and that all people should therefore be celibate, including married couples. Predictably, the original Shaker community that peaked at 6,000 full members in 1840 dwindled to three members by 2009.[198]

In some cases, the sexual intercourse between two people is seen as counter to religious law or doctrine. In many religious communities, including the Catholic Church and Mahayana Buddhists, religious leaders are expected to refrain from sexual intercourse in order to devote their full attention, energy, and loyalty to their religious duties.[199]

Opposition to same-sex marriage is largely based on the belief that sexual intercourse and sexual orientation should be of a heterosexual nature.[200][201][202][203] The recognition of such marriages is a civil rights, political, social, moral and religious issue in many nations, and the conflicts arise over whether same-sex couples should be allowed to enter into marriage, be required to use a different status (such as a civil union, which either grant equal rights as marriage or limited rights in comparison to marriage), or not have any such rights. A related issue is whether the term marriage should be applied.[204][205][206]

Other animals

See also: Sexual coercion
Mating houseflies

With regard to zoology, copulation is often termed the process in which a male introduces sperm into the female's body, especially directly into her reproductive tract.[21][29] Spiders have separate male and female sexes. Before mating and copulation, the male spider spins a small web and ejaculates on to it. He then stores the sperm in reservoirs on his large pedipalps, from which he transfers sperm to the female's genitals. The females can store sperm indefinitely.[207]

Many animals that live in water use external fertilization, whereas internal fertilization may have developed from a need to maintain gametes in a liquid medium in the Late Ordovician epoch. Internal fertilization with many vertebrates (such as reptiles, some fish, and most birds) occur via cloacal copulation (see also hemipenis), while mammals copulate vaginally, and many basal vertebrates reproduce sexually with external fertilization.[208][57]

For primitive insects, the male deposits spermatozoa on the substrate, sometimes stored within a special structure; courtship involves inducing the female to take up the sperm package into her genital opening, but there is no actual copulation.[209][210] In groups that have reproduction similar to spiders, such as dragonflies, males extrude sperm into secondary copulatory structures removed from their genital opening, which are then used to inseminate the female. In dragonflies, it is a set of modified sternites on the second abdominal segment.[211] In advanced groups of insects, the male uses its aedeagus, a structure formed from the terminal segments of the abdomen, to deposit sperm directly (though sometimes in a capsule called a spermatophore) into the female's reproductive tract.[212]

Bonobos, chimpanzees and dolphins are species known to engage in heterosexual behaviors even when the female is not in estrus, which is a point in her reproductive cycle suitable for successful impregnation. These species are also known to engage in same-sex sexual behaviors.[23] In these animals, the use of sexual intercourse has evolved beyond reproduction to apparently serve additional social functions (such as bonding).[8]

See also

References

  1. ^ a b c Keath Roberts (2006). Sex. Lotus Press. p. 145. ISBN 8189093592. Retrieved August 17, 2012. 
  2. ^ a b c d e Wayne Weiten, Margaret A. Lloyd, Dana S. Dunn, Elizabeth Yost Hammer (2008). Psychology Applied to Modern Life: Adjustment in the 21st Century. Cengage Learning. pp. 422–423. ISBN 0495553395. Retrieved January 5, 2012. Vaginal intercourse, known more technically as coitus, involves inserting the penis into the vagina and (typically) pelvic thrusting. ... The man-above, or "missionary," position is the most common [sex position]. 
  3. ^ a b Sexual intercourse most commonly means penile-vaginal penetration for sexual pleasure and/or sexual reproduction; dictionary sources state that it especially means this, and scholarly sources over the years agree. See, for example;
    • "Sexual intercourse". Merriam-Webster. Retrieved December 5, 2014. 
    • "Sexual intercourse". Collins English Dictionary. Retrieved September 5, 2012. 
    • Richard M. Lerner, Laurence Steinberg (2004). Handbook of Adolescent Psychology. John Wiley & Sons. pp. 193–196. ISBN 0471690449. Retrieved April 29, 2013. When researchers use the term sex, they nearly always mean sexual intercourse – more specifically, penile-vaginal intercourse... The widespread, unquestioned equation of penile-vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question matches what the researcher had in mind.' 
    • Fedwa Malti-Douglas (2007). Encyclopedia of Sex and Gender: A-C. Macmillan Reference. p. 308. ISBN 0028659619. Sexual intercourse. [T]he term coitus indicates a specific act of sexual intercourse that also is known as coition or copulation. This 'coming together' is generally understood in heteronormative terms as the penetration of a woman's vagina by a man's penis. 
    • Irving B. Weiner, W. Edward Craighead (2010). The Corsini Encyclopedia of Psychology, Volume 4. John Wiley & Sons. p. 1577. ISBN 0470170239. Retrieved August 21, 2013. Human sexual intercourse, or coitus, is one of the most common sexual outlets among adults. Sexual intercourse generally refers to penile penetration of the vagina... 
    • Clint E. Bruess, Elizabeth Schroeder (2013). Sexuality Education Theory and Practice. Jones & Bartlett Publishers. p. 152. ISBN 1449649289. Retrieved December 5, 2014. Vaginal sex is defined as when a penis or sex toy is inserted into a vagina for pleasure. In many cultures around the world, vaginal sex is what is usually implied when people refer to 'having sex' or 'sexual intercourse.' It is the most frequently studied behavior and is often the focus of sexuality education programming for youth. 
  4. ^ a b c Sandra Alters, Wendy Schiff (2012). Essential Concepts for Healthy Living. Jones & Bartlett Publishers. pp. 180–181. ISBN 1449630626. Retrieved August 31, 2013. Most heterosexuals are familiar with the notion of 'having sex' or sexual intercourse as vaginal sex, the insertion of a penis into a vagina. Vaginal sex, or coitus, is the most common and popular form of intimate sexual activity between partners. 
  5. ^ a b c d "Sexual Intercourse". Discovery.com. Archived from the original on 2008-08-22. Retrieved 2008-01-12. 
  6. ^ a b c d Nilamadhab Kar, Gopal Chandra Kar (2005). Comprehensive Textbook of Sexual Medicine. Jaypee Brothers Publishers. pp. 107–112. ISBN 8180614050. Retrieved September 4, 2012. 
  7. ^ Virginia Rutter, Pepper Schwartz (2011). The Gender of Sexuality: Exploring Sexual Possibilities. Rowman & Littlefield Publishers. p. 76. ISBN 0742570053. 
  8. ^ a b c d e f g h Diamond, Jared (1991). The Rise and Fall of the Third Chimpanzee. Radius. pp. 360 pages. ISBN 0091742684. 
  9. ^ a b c d Richard M. Lerner, Laurence Steinberg (2004). Handbook of Adolescent Psychology. John Wiley & Sons. pp. 193–196. ISBN 0471690449. Retrieved April 29, 2013. When researchers use the term sex, they nearly always mean sexual intercourse – more specifically, penile-vaginal intercourse... The widespread, unquestioned equation of penile-vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question matches what the researcher had in mind.' 
  10. ^ a b c d See page 11 onwards and pages 47–49 for views on what constitutes virginity loss and therefore sexual intercourse or other sexual activity; source discusses how gay and lesbian individuals define virginity loss, and how the majority of researchers and heterosexuals define virginity loss/"technical virginity" by whether or not a person has engaged in penile-vaginal sex. Laura M. Carpenter (2005). Virginity Lost: An Intimate Portrait of First Sexual Experiences. NYU Press. pp. 295 pages. ISBN 0-8147-1652-0. Retrieved October 9, 2011. 
  11. ^ a b c d e "Global strategy for the prevention and control of sexually transmitted infections: 2006–2015. Breaking the chain of transmission". World Health Organization. 2007. Retrieved November 26, 2011. 
  12. ^
  13. ^
  14. ^ a b c d Ada P. Kahn, Jan Fawcett (2008). The Encyclopedia of Mental Health. Infobase Publishing. p. 111. ISBN 0816064547. Retrieved September 5, 2012. 
  15. ^ a b c Randall, H. E., & Byers, S. E. (2003). "What is sex? Students' definitions of having sex, sexual partner, and unfaithful sexual behaviour". The Canadian Journal of Human Sexuality 12: 87–96. Recently, researchers in the United States, the United Kingdom, and Australia have investigated university students' definitions of having sex. These studies found that students differ in their opinions of what sexual behaviours constitute having sex (Pitts & Rahman, 2001; Richters & Song, 1999; Sanders & Reinisch, 1999). While the vast majority of respondents (more than 97%) in these three studies included penile-vaginal intercourse in their definition of sex, fewer (between 70% and 90%) respondents considered penile-anal intercourse to constitute having sex. Oral-genital behaviours were defined as sex by between 32% and 58% of respondents. 
  16. ^ a b c "Defining sexual health: Report of a technical consultation on sexual health". World Health Organization. January 2002. p. 4. Retrieved September 5, 2012. In English, the term 'sex' is often used to mean 'sexual activity' and can cover a range of behaviours. Other languages and cultures use different terms, with slightly different meanings. 
  17. ^ "Sexually Transmitted Disease Surveillance". Centers for Disease Control and Prevention (CDC). 2008. Retrieved December 6, 2011.  Also see Fact Sheet
  18. ^ a b c d e f Dianne Hales (2008). An Invitation to Health Brief 2010–2011. Cengage Learning. pp. 269–271. ISBN 0495391921. Retrieved August 29, 2013. 
  19. ^ a b Bhushan Kumar, Somesh Gupta (2014). Sexually Transmitted Infections. Elsevier Health Sciences. p. 237. ISBN 8131229785. Retrieved December 6, 2014. 
  20. ^ Bryan Strong, Christine DeVault, Theodore F. Cohen (2010). The Marriage and Family Experience: Intimate Relationship in a Changing Society. Cengage Learning. p. 186. ISBN 0-534-62425-1. Retrieved October 8, 2011. Most people agree that we maintain virginity as long as we refrain from sexual (vaginal) intercourse. ...But occasionally we hear people speak of 'technical virginity' ... Other research, especially research looking into virginity loss, reports that 35% of virgins, defined as people who have never engaged in vaginal intercourse, have nonetheless engaged in one or more other forms of heterosexual activity (e.g. oral sex, anal sex, or mutual masturbation). ... Data indicate that 'a very significant proportion of teens ha[ve] had experience with oral sex, even if they haven't had sexual intercourse, and may think of themselves as virgins'. 
  21. ^ a b Michael Kent (2000). Advanced biology. Oxford University Press. pp. 250–253. ISBN 0199141959. 
  22. ^ Showick Thorpe, Edgar Thorpe (2009). The Pearson General Studies Manual 2009, 1/e. Pearson Education India. p. page 17 (xvii). ISBN 8131721337. 
  23. ^ a b c
  24. ^ Balcombe, Jonathan (2006). Pleasurable Kingdom: Animals and the Nature of Feeling Good. Palgrave Macmillan. pp. 106–118. ISBN 0230552277. 
  25. ^
  26. ^ a b c d e f g See page 302 for orgasm information, and pages 285–286 for definitions, prevalence and length of sexual intercourse. Janell L. Carroll (2012). Discovery Series: Human Sexuality, 1st ed.. Cengage Learning. pp. 656 pages. ISBN 1111841896. Retrieved August 25, 2013. 
  27. ^ Harvey B. Milkman, Kenneth W. Wanberg (2004). Pathways to Self-Discovery and Change: Criminal Conduct and Substance Abuse Treatment for Adolescents. SAGE. pp. 254–255. ISBN 1412906148. Retrieved September 6, 2013. 
  28. ^ a b Human Kinetics (2009). Health and Wellness for Life. Human Kinetics. p. 207. ISBN 0736068503. Retrieved October 11, 2013. 
  29. ^ a b "Copulation". Dorland's Medical Dictionary for Health Consumers, 2007/TheFreeDictionary.com for various dictionary definitions. Retrieved September 6, 2012. 
  30. ^ "Copulation". The American Heritage Dictionary of the English Language, Fifth Edition. 2011. Retrieved August 23, 2013. 
  31. ^ a b Edward M. Barrows (2011). Animal Behavior Desk Reference: A Dictionary of Animal Behavior, Ecology, and Evolution. Taylor & Francis. pp. 122–124. ISBN 1439836515. Retrieved August 25, 2013. 
  32. ^
    • Ken Plummer (2002). Modern Homosexualities: Fragments of Lesbian and Gay Experiences. Routledge. pp. 187–191. ISBN 1134922426. Retrieved August 24, 2013. [S]ome sexual practices are regarded as inherently better (normal, natural, more satisfying) than others, with vaginal intercourse privileged as the 'Real Thing.' Such beliefs, influenced by views about sex as ultimately a reproductive function, continue to be perpetuated through discourses on sex despite a number of important contradictions. 
    • Richard M. Lerner, Laurence Steinberg (2004). Handbook of Adolescent Psychology. John Wiley & Sons. pp. 193–196. ISBN 0471690449. Retrieved April 29, 2013. When researchers use the term sex, they nearly always mean sexual intercourse – more specifically, penile-vaginal intercourse... The widespread, unquestioned equation of penile-vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question matches what the researcher had in mind.' 
    • See page 11 onwards and pages 47–49 for views on what constitutes virginity loss and therefore sexual intercourse or other sexual activity; source discusses how gay and lesbian individuals define virginity loss, and how the majority of researchers and heterosexuals define virginity loss/"technical virginity" by whether or not a person has engaged in penile-vaginal sex. Laura M. Carpenter (2005). Virginity Lost: An Intimate Portrait of First Sexual Experiences. NYU Press. pp. 295 pages. ISBN 0-8147-1652-0. Retrieved October 9, 2011. 
    • Fedwa Malti-Douglas (2007). Encyclopedia of Sex and Gender: A-C. Macmillan Reference. p. 308. ISBN 0028659619. Sexual intercourse. [T]he term coitus indicates a specific act of sexual intercourse that also is known as coition or copulation. This 'coming together' is generally understood in heteronormative terms as the penetration of a woman's vagina by a man's penis. 
    • Irving B. Weiner, W. Edward Craighead (2010). The Corsini Encyclopedia of Psychology, Volume 4. John Wiley & Sons. p. 1577. ISBN 0470170239. Retrieved August 21, 2013. Human sexual intercourse, or coitus, is one of the most common sexual outlets among adults. Sexual intercourse generally refers to penile penetration of the vagina... 
    • Clint E. Bruess, Elizabeth Schroeder (2013). Sexuality Education Theory and Practice. Jones & Bartlett Publishers. p. 152. ISBN 1449649289. Retrieved December 5, 2014. Vaginal sex is defined as when a penis or sex toy is inserted into a vagina for pleasure. In many cultures around the world, vaginal sex is what is usually implied when people refer to 'having sex' or 'sexual intercourse.' It is the most frequently studied behavior and is often the focus of sexuality education programming for youth. 
  33. ^ a b c d e Cox, Lauren (March 8, 2010). "Study: Adults Can't Agree What 'Sex' Means". ABC.com. Retrieved September 5, 2012. 
  34. ^ "Fuck". Merriam-Webster. Retrieved March 30, 2013. 
  35. ^ "Sleep together". TheFreeDictionary.com. Retrieved March 30, 2013. 
  36. ^ "Intromission". Merriam-Webster. Retrieved December 26, 2012. 
  37. ^
  38. ^ a b Ken Plummer (2002). Modern Homosexualities: Fragments of Lesbian and Gay Experiences. Routledge. pp. 187–191. ISBN 1134922426. Retrieved August 24, 2013. [S]ome sexual practices are regarded as inherently better (normal, natural, more satisfying) than others, with vaginal intercourse privileged as the 'Real Thing.' Such beliefs, influenced by views about sex as ultimately a reproductive function, continue to be perpetuated through discourses on sex despite a number of important contradictions. 
  39. ^ a b Andrew Baum, Tracey A. A. Revenson, Jerome Singer (2012). Handbook of Health Psychology, 2nd Edition. Psychology Press. pp. 259–260. ISBN 080586461X. Retrieved April 30, 2013. 
  40. ^ Arthur G. Miller (1999). Perspectives on Evil and Violence. Psychology Press. p. 240. ISBN 0805897844. Retrieved April 29, 2013. Many people consider penile-vaginal intercourse the only form of 'real' sex. 
  41. ^ a b Pamela J. Kalbfleisch, Michael J. Cody (2012). Gender Power and Communication in Human Relationships. Routledge. p. 218. ISBN 1136480501. Retrieved April 30, 2013. 
  42. ^
  43. ^ a b
    • Ken Plummer (2002). Modern Homosexualities: Fragments of Lesbian and Gay Experiences. Routledge. pp. 187–191. ISBN 1134922426. Retrieved August 24, 2013. The social construction of 'sex' as vaginal intercourse affects how other forms of sexual activity are evaluated as sexually satisfying or arousing; in some cases whether an activity is seen as a sexual act at all. For example, unless a woman has been penetrated by a man's penis she is still technically a virgin even if she has had lots of sexual experience. 
    • Randall, H. E., & Byers, S. E. (2003). "What is sex? Students' definitions of having sex, sexual partner, and unfaithful sexual behaviour". The Canadian Journal of Human Sexuality 12: 87–96. Recently, researchers in the United States, the United Kingdom, and Australia have investigated university students' definitions of having sex. These studies found that students differ in their opinions of what sexual behaviours constitute having sex (Pitts & Rahman, 2001; Richters & Song, 1999; Sanders & Reinisch, 1999). While the vast majority of respondents (more than 97%) in these three studies included penile-vaginal intercourse in their definition of sex, fewer (between 70% and 90%) respondents considered penile-anal intercourse to constitute having sex. Oral-genital behaviours were defined as sex by between 32% and 58% of respondents. 
    • See page 11 onwards and pages 47–49 for views on what constitutes virginity loss and therefore sexual intercourse or other sexual activity; source discusses how gay and lesbian individuals define virginity loss, and how the majority of researchers and heterosexuals define virginity loss/"technical virginity" by whether or not a person has engaged in penile-vaginal sex. Laura M. Carpenter (2005). Virginity Lost: An Intimate Portrait of First Sexual Experiences. NYU Press. pp. 295 pages. ISBN 0-8147-1652-0. Retrieved October 9, 2011. 
    • Bryan Strong, Christine DeVault, Theodore F. Cohen (2010). The Marriage and Family Experience: Intimate Relationship in a Changing Society. Cengage Learning. p. 186. ISBN 0-534-62425-1. Retrieved October 8, 2011. Most people agree that we maintain virginity as long as we refrain from sexual (vaginal) intercourse. ...But occasionally we hear people speak of 'technical virginity' ... Other research, especially research looking into virginity loss, reports that 35% of virgins, defined as people who have never engaged in vaginal intercourse, have nonetheless engaged in one or more other forms of heterosexual activity (e.g. oral sex, anal sex, or mutual masturbation). ... Data indicate that 'a very significant proportion of teens ha[ve] had experience with oral sex, even if they haven't had sexual intercourse, and may think of themselves as virgins'. 
    • Robert Crooks, Karla Baur (2010). Our Sexuality. Cengage Learning. pp. 286–289. ISBN 0495812943. Retrieved August 30, 2012. Noncoital forms of sexual intimacy, which have been called outercourse, can be a viable form of birth control. Outercourse includes all avenues of sexual intimacy other than penile–vaginal intercourse, including kissing, touching, mutual masturbation, and oral and anal sex. 
  44. ^ Joseph Gross, Michael (2003). Like a Virgin. The Advocate/Here Publishing. pp. 44–45. 0001-8996. Retrieved 2011-03-13. 
  45. ^ Dolby, Tom (February 2004). "Why Some Gay Men Don't Go All The Way". Out. pp. 76–77. Retrieved 2011-02-12. 
  46. ^ Karen Bouris (1995). What Parents and Teenage Girls Should Know about "Losing Your Virginity". Conari Press. pp. 133–134. ISBN 0-943233-93-3. 
  47. ^ Jerrold S. Greenberg, Clint E. Bruess, Sarah C. Conklin (2007). Exploring the Dimensions of Human Sexuality. Jones & Bartlett Learning. p. 429. ISBN 0-7637-4148-5. 9780763741488. Retrieved 2010-12-19. 
  48. ^ Michael R Kauth (2000). True Nature: A Theory of Sexual Attraction. Springer. p. 74. ISBN 0306463903. Retrieved August 30, 2012. 
  49. ^ Jayson, Sharon (October 19, 2005). "'Technical virginity' becomes part of teens' equation". USA Today. Retrieved August 7, 2009. 
  50. ^ a b c "Oral Sex and HIV Risk". Centers for Disease Control and Prevention (CDC). June 2009. Retrieved August 30, 2013. 
  51. ^ a b c Jonathan Engel (2009). The Epidemic: A History of Aids. HarperCollins. p. 242. ISBN 0061856762. Retrieved August 30, 2013. Many men simply did not like the feel of condoms, or associated them with emasculation. They say, 'Unless it's flesh on flesh, it's not real sex... 
  52. ^ a b Naomi N. Wekwete (2010). Adolescent Pregnancy Challenges in the Era of HIV and AIDS: A Case Study of a Selected Rural Area in Zimbabwe. African Books Collective. p. 49. ISBN 9994455486. Retrieved August 30, 2013. 
  53. ^ a b Harry T. Reis, Susan Sprecher, Susan K. Sprecher (2009). Encyclopedia of Human Relationships, Volume 1. SAGE. pp. 541–543. ISBN 1412958466. 
  54. ^ Taormino, Tristan (2009). The Big Book of Sex Toys. Quiver. p. 52. ISBN 978-1-59233-355-4. Retrieved June 9, 2014. 
  55. ^ a b c d e Wayne Weiten, Dana S. Dunn, Elizabeth Yost Hammer (2011). Psychology Applied to Modern Life: Adjustment in the 21st Century. Cengage Learning. pp. 384–386. ISBN 1-111-18663-4. Retrieved January 5, 2012. 
  56. ^ Sandra Alters, Wendy Schiff (2011). Essential Concepts for Healthy Living Update. Jones & Bartlett Publishers. p. 154. ISBN 144965374X. Retrieved December 9, 2014. 
  57. ^ a b Cecie Starr, Beverly McMillan (2008). Human Biology. Cengage Learning. p. 314. ISBN 0495561819. Retrieved April 30, 2013. 
  58. ^ Joseph A. Flaherty, John Marcell Davis, Philip G. Janicak (1993). Psychiatry: Diagnosis & therapy. A Lange clinical manual. Appleton & Lange (Original from Northwestern University). pp. 544 pages. ISBN 0-8385-1267-4. The amount of time of sexual arousal needed to reach orgasm is variable — and usually much longer — in women than in men; thus, only 20–30% of women attain a coital climax. b. Many women (70–80%) require manual clitoral stimulation... 
  59. ^ Mah K, Binik YM (January 7, 2001). "The nature of human orgasm: a critical review of major trends". Clinical Psychology Review 21 (6): 823–856. doi:10.1016/S0272-7358(00)00069-6. PMID 11497209. Women rated clitoral stimulation as at least somewhat more important than vaginal stimulation in achieving orgasm; only about 20% indicated that they did not require additional clitoral stimulation during intercourse. 
  60. ^ Kammerer-Doak D, Rogers RG (June 2008). "Female Sexual Function and Dysfunction". Obstetrics and Gynecology Clinics of North America 35 (2): 169–183. doi:10.1016/j.ogc.2008.03.006. PMID 18486835. Most women report the inability to achieve orgasm with vaginal intercourse and require direct clitoral stimulation ... About 20% have coital climaxes... 
  61. ^ Elisabeth Anne Lloyd (2005). The case of the female orgasm: bias in the science of evolution. Harvard University Press. p. 53. ISBN 0-674-01706-4. Retrieved January 5, 2012. 
  62. ^ O'Connell HE, Sanjeevan KV, Hutson JM (October 2005). "Anatomy of the clitoris". The Journal of Urology 174 (4 Pt 1): 1189–95. doi:10.1097/01.ju.0000173639.38898.cd. PMID 16145367. Lay summaryBBC News (11 June 2006). 
  63. ^ Hurlbert DF, Apt C (1995). "The coital alignment technique and directed masturbation: a comparative study on female orgasm". Journal of Sex & Marital Therapy. 21(1) (1): 21–29. doi:10.1080/00926239508405968. PMID 7608994. 
  64. ^ Barry R. Komisaruk, Beverly Whipple, Sara Nasserzadeh, Carlos Beyer-Flores (2009). The Orgasm Answer Guide. JHU Press. pp. 108–109. ISBN 0-8018-9396-8. Retrieved November 6, 2011. 
  65. ^ Paula Kamen (2000). Her Way: Young Women Remake the Sexual Revolution. New York University Press. pp. 74–77. ISBN 0814747337. Retrieved September 5, 2012. 
  66. ^ Hite, Shere (2003). The Hite Report: A Nationwide Study of Female Sexuality. New York, NY: Seven Stories Press. pp. 512 pages. ISBN 1-58322-569-2. Retrieved March 2, 2012. 
  67. ^ Carroll, Janell L. (2009). Sexuality Now: Embracing Diversity. Cengage Learning. pp. 118, 252, and 264. ISBN 978-0-495-60274-3. Retrieved 23 June 2012. The majority of women enjoy a light caressing of the shaft of the clitoris, together with an occasional circling of the [clitoral glans], and maybe digital (finger) penetration of the vagina. Other women dislike direct stimulation and prefer to have the [clitoral glans] rolled between the lips of the labia. Some women like to have the entire area of the vulva caressed, whereas others like the caressing to be focused on the [clitoral glans]. Women report that clitoral stimulation feels best when the fingers are well lubricated. 
  68. ^ Pappas, Stephanie (October 22, 2014). "Sex Is 385 Million Years Old, and It Looked Like Square Dancing". Live Science. Retrieved October 27, 2014. 
  69. ^ a b Richard Evan Jones, Kristin H. López (2006). Human Reproductive Biology. Academic Press. pp. 604 pages. ISBN 0120884658. Retrieved November 8, 2012. 
  70. ^ Jared Diamond (1997). Why Is Sex Fun?. Basic Books. ISBN 0-465-03127-7. 
  71. ^ James Bobick, Naomi Balaban (2008). The Handy Anatomy Answer Book. Visible Ink Press. pp. 306–307. ISBN 157859328X. Retrieved August 21, 2013. 
  72. ^ R.K. Sharma (2007). Concise Textbook Of Forensic Medicine & Toxicology. Elsevier India. pp. 113–116. ISBN 8131211452. Retrieved October 13, 2013. 
  73. ^ Mosby, Marie T. O'Toole (2013). Mosby's Medical Dictionary. Elsevier Health Sciences. p. 138. ISBN 0323112587. Retrieved October 13, 2013. 
  74. ^ Berkowitz D, Marsiglio W (2007). "Gay Men: Negotiating Procreative, Father, and Family Identities". Journal of Marriage and Family 69 (2): 366–381. doi:10.1111/j.1741-3737.2007.00371.x. 
  75. ^ a b Joan M. Burda (2008). Gay, lesbian, and transgender clients: a lawyer's guide. American Bar Association. pp. 69–74. ISBN 1-59031-944-3. Retrieved July 28, 2011. 
  76. ^ Elizabeth Bernstein, Laurie Schaffner (2005). Regulating sex: the politics of intimacy and identity. Perspectives on gender. Psychology Press. p. 22. ISBN 0-415-94869-X. Retrieved July 28, 2011. 
  77. ^ Jerry D. Durham, Felissa R. Lashley (2000). The Person With HIV/AIDS: Nursing Perspectives, 3rd Edition. Springer Publishing Company. p. 103. ISBN 8122300049. Retrieved January 29, 2012. 
  78. ^ Robert Crooks, Karla Baur (2010). Our Sexuality. Cengage Learning. pp. 286–289. ISBN 0495812943. Retrieved August 30, 2012. Noncoital forms of sexual intimacy, which have been called outercourse, can be a viable form of birth control. Outercourse includes all avenues of sexual intimacy other than penile–vaginal intercourse, including kissing, touching, mutual masturbation, and oral and anal sex. 
  79. ^ Feldmann J, Middleman AB (2002). "Adolescent sexuality and sexual behavior". Current opinion in obstetrics & gynecology 14 (5): 489–493. doi:10.1097/00001703-200210000-00008. PMID 12401976. 
  80. ^ Thomas, R. Murray (2009). Sex and the American teenager seeing through the myths and confronting the issues. Lanham, Md.: Rowman & Littlefield Education. p. 81. ISBN 9781607090182. 
  81. ^ Edlin, Gordon (2012). Health & Wellness.. Jones & Bartlett Learning. p. 213. ISBN 9781449636470. 
  82. ^ a b c Chin HB, Sipe TA, Elder R, Mercer SL, Chattopadhyay SK, Jacob V, Wethington HR, Kirby D, Elliston DB, Griffith M, Chuke SO, Briss SC, Ericksen I, Galbraith JS, Herbst JH, Johnson RL, Kraft JM, Noar SM, Romero LM, Santelli J (2012). "The Effectiveness of Group-Based Comprehensive Risk-Reduction and Abstinence Education Interventions to Prevent or Reduce the Risk of Adolescent Pregnancy, Human Immunodeficiency Virus, and Sexually Transmitted Infections". American Journal of Preventive Medicine 42 (3): 272–294. doi:10.1016/j.amepre.2011.11.006. PMID 22341164. 
  83. ^ National Institute of Allergy and Infectious Diseases; National Institutes of Health, Department of Health and Human Services (July 20, 2001). "Workshop Summary: Scientific Evidence on Condom Effectiveness for Sexually Transmitted Disease (STD) Prevention" (PDF). Hyatt Dulles Airport, Herndon, Virginia. pp. 13–15. Archived from the original on March 15, 2010. Retrieved March 20, 2009. 
  84. ^ "Effectiveness of male latex condoms in protecting against pregnancy and sexually transmitted infections". World Health Organization. 2000. Retrieved July 23, 2013. 
  85. ^ Winner B, Peipert JF, Zhao Q, Buckel C, Madden T, Allsworth JE, Secura GM (2012). "Effectiveness of long-acting reversible contraception". N. Engl. J. Med. 366 (21): 1998–2007. doi:10.1056/NEJMoa1110855. PMID 22621627. 
  86. ^ "Contraceptive Use". Guttmacher Institute. 2010. Retrieved March 4, 2011. 
  87. ^ "Sexual Health Statistics for Teenagers and Young Adults in the United States" (PDF). Kaiser Family Foundation. September 2006. Retrieved 2008-07-02. 
  88. ^ "Findings from the National Survey of Sexual Health and Behavior, Centre for Sexual Health Promotion, Indiana University". The Journal of Sexual Medicine. 7, Supplement 5.: 4 2010. Retrieved March 4, 2011. 
  89. ^ Clint E. Bruess, Elizabeth Schroeder (2013). Sexuality Education Theory and Practice. Jones & Bartlett Publishers. p. 152. ISBN 1449649289. Retrieved December 5, 2014. 
  90. ^ a b c d Bozon, Michael (2003). "At what age do women and men have their first sexual intercourse? World comparisons and recent trends". Population and Societies 391: 1–4. 
  91. ^ a b c d Graziella Caselli, Guillaume Wunsch, Daniel Courgeau, Jacques Vallin (2005). Demography – Analysis and Synthesis: A Treatise in Population. Academic Press. pp. 490–501. ISBN 012765660X. Retrieved September 6, 2013. 
  92. ^ "Sexual and Reproductive Health: Women and Men". Guttmacher Institute. 2002. Archived from the original on July 26, 2011. Retrieved December 26, 2012. 
  93. ^ "Seventeen Is the Average Age at First Sexual Intercourse" (pdf). American Sexual Behavior. newstrategist.com. Archived from the original on January 24, 2013. Retrieved March 23, 2013. 
  94. ^ "Fertility, Family Planning, and Reproductive Health of U.S.Women: Data From the 2002 National Survey of Family Growth". Centers for Disease Control and Prevention (CDC). Retrieved 9 February 2013. 
  95. ^ "Fertility, Contraception, and Fatherhood: Data on Men and Women From Cycle 6 (2002) of the National Survey of Family Growth". Centers for Disease Control and Prevention (CDC). Retrieved 9 February 2013. 
  96. ^ "Key Statistics from the National Survey of Family Growth". Centers for Disease Control and Prevention (CDC). Retrieved 9 February 2013. 
  97. ^ a b "Teenagers in the United States: Sexual Activity, Contraceptive Use, and Childbearing, 2006–2010 National Survey of Family Growth" (pdf). Centers for Disease Control and Prevention (CDC). Retrieved December 26, 2012. 
  98. ^ a b "Teenagers in the United States: Sexual Activity, Contraceptive Use, and Childbearing, 2002". Centers for Disease Control and Prevention (CDC). Retrieved 9 February 2013. 
  99. ^ a b Denis Campbell (January 22, 2006). "No sex please until we're at least 17 years old, we're British". The Observer. Retrieved March 14, 2013. 
  100. ^ "Teen Sex Survey". Channel 4. 2008. Retrieved August 5, 2011. 
  101. ^ a b Andrew Steptoe, Kenneth Freedland, J. Richard Jennings, Maria M. Llabre, Stephen B Manuck, Elizabeth J. Susman (2010). Handbook of Behavioral Medicine: Methods and Applications. Springer Science & Business Media. pp. 60–61. ISBN 0387094881. Retrieved December 7, 2014. 
  102. ^ a b Theresa Hornstein, Jeri Schwerin (2012). Biology of Women. Cengage Learning. p. 205. ISBN 1285401026. Retrieved December 7, 2014. 
  103. ^ Carol Sigelman, Elizabeth Rider (2011). Life-Span Human Development. Cengage Learning. p. 452. ISBN 1111342733. Retrieved December 7, 2014. 
  104. ^ Northrup, Christiane (2010). Women's Bodies, Women's Wisdom: Creating Physical and Emotional Health and Healing. Bantam. p. 960. ISBN 978-0-553-80793-6. 
  105. ^ a b c d "Sexually transmitted infections". Fact sheet N° 110. World Health Organization. August 2011. Retrieved 8 September 2012. 
  106. ^ CDC Hepatitis B Information for Health Professionals Accessed May 27, 2010
  107. ^ "Hepatitis B". World Health Organization. Retrieved 15 September 2012. 
  108. ^ "STD Trends in the United States: 2010 National Data for Gonorrhea, Chlamydia, and Syphilis". Centers for Disease Control and Prevention. Retrieved 15 September 2012. 
  109. ^ "HIV/AIDS". World Health Organization. Retrieved 15 September 2012. 
  110. ^ "HIV/AIDS". Fact sheet N° 360. World Health Organization. July 2012. Retrieved 8 September 2012. 
  111. ^ "Not Every Pregnancy is Welcome". The world health report 2005 – make every mother and child count. World Health Organization. Retrieved 6 December 2011. 
  112. ^ "Get "In the Know": 20 Questions About Pregnancy, Contraception and Abortion". Guttmacher Institute. 2005. Retrieved March 4, 2011. 
  113. ^ Ventura, SJ, Abma, JC, Mosher, WD, & Henshaw, S. (2007-11-16). "Estimated pregnancy rates for the United States, 1990–2000: An Update. National Vital Statistics Reports, 52 (23)". Centers for Disease Control and Prevention. Retrieved March 4, 2011. 
  114. ^ Christine Webber, psychotherapist and Dr David Delvin. "Talking to pre-adolescent children about sex". Broaching the subject. Net Doctor. Retrieved August 5, 2011. 
  115. ^ a b Nicolas Kipshidze, Jawad Fareed, Patrick W. Serruys, Jeff Moses (2007). Textbook of Interventional Cardiovascular Pharmacology. CRC Press. p. 505. ISBN 0203463048. 
  116. ^ a b c Dahabreh, Issa J. (23 March 2011). "Association of Episodic Physical and Sexual Activity With Triggering of Acute Cardiac Events. Systematic Review and Meta-analysis.". JAMA: The Journal of the American Medical Association 305 (12): 1225. doi:10.1001/jama.2011.336. Acute cardiac events were significantly associated with episodic physical and sexual activity; this association was attenuated among persons with high levels of habitual physical activity. 
  117. ^ Pfortmueller CA, Koetter JN, Zimmermann H, Exadaktylos AK (2012). "Sexual activity-related emergency department admissions: Eleven years of experience at a Swiss university hospital". Emergency Medicine Journal 30 (10): 846–850. doi:10.1136/emermed-2012-201845. PMID 23100321. 
  118. ^ a b Blum K, Werner T, Carnes S, Carnes P, Bowirrat A, Giordano J, Oscar-Berman M, Gold M (2012). "Sex, drugs, and rock 'n' roll: hypothesizing common mesolimbic activation as a function of reward gene polymorphisms". J. Psychoactive Drugs 44 (1): 38–55. doi:10.1080/02791072.2012.662112. PMC 4040958. PMID 22641964. It has been found that deltaFosB gene in the NAc is critical for reinforcing effects of sexual reward. Pitchers and colleagues (2010) reported that sexual experience was shown to cause DeltaFosB accumulation in several limbic brain regions including the NAc, medial pre-frontal cortex, VTA, caudate, and putamen, but not the medial preoptic nucleus. Next, the induction of c-Fos, a downstream (repressed) target of DeltaFosB, was measured in sexually experienced and naive animals. The number of mating-induced c-Fos-IR cells was significantly decreased in sexually experienced animals compared to sexually naive controls. Finally, DeltaFosB levels and its activity in the NAc were manipulated using viral-mediated gene transfer to study its potential role in mediating sexual experience and experience-induced facilitation of sexual performance. Animals with DeltaFosB overexpression displayed enhanced facilitation of sexual performance with sexual experience relative to controls. In contrast, the expression of DeltaJunD, a dominant-negative binding partner of DeltaFosB, attenuated sexual experience-induced facilitation of sexual performance, and stunted long-term maintenance of facilitation compared to DeltaFosB overexpressing group. Together, these findings support a critical role for DeltaFosB expression in the NAc in the reinforcing effects of sexual behavior and sexual experience-induced facilitation of sexual performance. ... both drug addiction and sexual addiction represent pathological forms of neuroplasticity along with the emergence of aberrant behaviors involving a cascade of neurochemical changes mainly in the brain's rewarding circuitry. 
  119. ^ a b Olsen CM (December 2011). "Natural rewards, neuroplasticity, and non-drug addictions". Neuropharmacology 61 (7): 1109–1122. doi:10.1016/j.neuropharm.2011.03.010. PMC 3139704. PMID 21459101. 
  120. ^ a b Pitchers KK, Vialou V, Nestler EJ, Laviolette SR, Lehman MN, Coolen LM (February 2013). "Natural and drug rewards act on common neural plasticity mechanisms with ΔFosB as a key mediator". J. Neurosci. 33 (8): 3434–42. doi:10.1523/JNEUROSCI.4881-12.2013. PMC 3865508. PMID 23426671. Together, these findings demonstrate that drugs of abuse and natural reward behaviors act on common molecular and cellular mechanisms of plasticity that control vulnerability to drug addiction, and that this increased vulnerability is mediated by ΔFosB and its downstream transcriptional targets. 
  121. ^ a b John Wincze (2009). Enhancing Sexuality : A Problem-Solving Approach to Treating Dysfunction. Oxford University Press. pp. 56–57. ISBN 0199718024. 
  122. ^ a b c Hartmut Porst, Jacques Buvat (2008). Standard Practice in Sexual Medicine. John Wiley & Sons. p. 189. ISBN 1405178728. Retrieved October 22, 2013. 
  123. ^ a b c Emmanuele A. Jannini, Chris G. McMahon, Marcel D. Waldinger (2012). Premature Ejaculation: From Etiology to Diagnosis and Treatment. Springer. pp. 159–162. ISBN 8847026466. Retrieved October 22, 2013. 
  124. ^ a b June M. Reinisch, Ruth Beasley (1991). The Kinsey Institute New Report On Sex. Macmillan. pp. 129–130. ISBN 0312063865. Retrieved August 30, 2012. 
  125. ^ Corty EW, Guardiani JM (2008). "Canadian and American Sex Therapists' Perceptions of Normal and Abnormal Ejaculatory Latencies: How Long Should Intercourse Last?". The Journal of Sexual Medicine 5 (5): 1251–1256. doi:10.1111/j.1743-6109.2008.00797.x. PMID 18331255. 
  126. ^ Vern L Bullough, RN, PhD, Faan, Vern L. Bullough, Bonnie Bullough (2014). Human Sexuality: An Encyclopedia. Routledge. p. 32. ISBN 1135825025. Retrieved December 6, 2014. 
  127. ^ Rosenthal, Martha (2012). Human Sexuality: From Cells to Society. Cengage Learning. p. 150. ISBN 9780618755714. Retrieved October 22, 2013. 
  128. ^ a b c Irving B. Weiner, George Stricker, Thomas A. Widiger (2012). Handbook of Psychology, Clinical Psychology. John Wiley & Sons. pp. 172–175. ISBN 1118404432. Retrieved October 22, 2013. 
  129. ^ Rod Plotnik, Haig Kouyoumdjian (2010). Introduction to Psychology. Cengage Learning. p. 344. ISBN 0495903442. Inhibited female orgasm refers to a persistent delay or absence of orgasm after becoming aroused and excited. About 10% of women never reach orgasm... 
  130. ^ Knoepp LR, Shippey SH, Chen CC, Cundiff GW, Derogatis LR, Handa VL (2010). "Sexual complaints, pelvic floor symptoms, and sexual distress in women over forty". The Journal of Sexual Medicine 7 (11): 3675–82. doi:10.1111/j.1743-6109.2010.01955.x. PMC 3163299. PMID 20704643. 
  131. ^ Fred F. Ferri (2012). Ferri's Clinical Advisor 2013,5 Books in 1, Expert Consult - Online and Print,1: Ferri's Clinical Advisor 2013. Elsevier Health Sciences. p. 1134. ISBN 0323083730. Retrieved November 29, 2014. 
  132. ^ a b Marlene B. Goldman, Rebecca Troisi, Kathryn M. Rexrode (2012). Women and Health. Academic Press. p. 351. ISBN 0123849799. Retrieved December 6, 2014. 
  133. ^ Ronald J. Comer (2010). Fundamentals of Abnormal Psychology. Macmillan. p. 338. ISBN 1429216336. Retrieved December 6, 2014. 
  134. ^ a b Schouten BW, Bohnen AM, Groeneveld FP, Dohle GR, Thomas S, Bosch JL (July 2010). "Erectile dysfunction in the community: trends over time in incidence, prevalence, GP consultation and medication use—the Krimpen study: trends in ED". J Sex Med 7 (7): 2547–53. doi:10.1111/j.1743-6109.2010.01849.x. PMID 20497307. 
  135. ^ "Premature ejaculation". Mayo Clinic.com. Retrieved 2007-03-02. 
  136. ^ "Guideline on the pharmacologic management of premature ejaculation". American Urological Association. 2004. Retrieved October 12, 2013. 
  137. ^ Jerrold S Greenberg, Clint E. Bruess, Dean Emeritus (2010). Exploring the Dimensions of Human Sexuality. Jones & Bartlett Publishers. p. 633. ISBN 0763797405. Retrieved December 8, 2014. 
  138. ^ Richard Balon, Robert Taylor Segraves (2009). Clinical Manual of Sexual Disorders. American Psychiatric Pub. p. 292. ISBN 1585629057. Retrieved December 6, 2014. 
  139. ^ The Architects' Journal, Volume 221, Issues 17-21. Architectural Press. 2005. p. 16. Retrieved December 6, 2014. 
  140. ^ Richard Balon, Robert Taylor Segraves (2009). Clinical Manual of Sexual Disorders. American Psychiatric Pub. p. 281. ISBN 1585629057. Retrieved December 6, 2014. 
  141. ^ a b Williamson GM, Walters AS (1996). "Perceived Impact of Limb Amputation on Sexual Activity: A Study of Adult Amputees". The Journal of Sex Research (Taylor & Francis Group (Lawrence Erlbaum Associates)) 33 (3): 221–230. doi:10.1080/00224499609551838. ISSN 0022-4499. JSTOR 3813582. OCLC 39109327. 
  142. ^ a b Donna Falvo (2013). Medical and Psychosocial Aspects of Chronic Illness and Disability. Jones & Bartlett Publishers. p. 367. ISBN 144969442X. Retrieved December 7, 2014. 
  143. ^ Alcohol Use and Sexual Risk Behaviour: A Cross-cultural Study in Eight Countries. World Health Organization. 2005. pp. 135 pages. ISBN 9241562897. Retrieved March 30, 2013. 
  144. ^ Peter Aggleton, Andrew Ball, Purnima Mane (2013). Sex, Drugs and Young People: International Perspectives. Routledge. pp. 130–133. ISBN 1134333099. Retrieved December 7, 2014. 
  145. ^ a b Comfort, Alex (1991). The New Joy of Sex: A Gourmet Guide to Lovemaking. Diane Publishing Company. pp. 253 pages. ISBN 0756783526. Retrieved August 16, 2013. 
  146. ^ a b Victor C. De Munck (1998). Romantic Love and Sexual Behavior: Perspectives from the Social Sciences. Greenwood Publishing Group. pp. 148–149. ISBN 0275957268. Retrieved December 9, 2014. 
  147. ^ a b Tasha R. Howe (2011). Marriages and Families in the 21st Century: A Bioecological Approach. John Wiley & Sons. p. 411. ISBN 1405195010. Retrieved December 9, 2014. 
  148. ^ a b c Mark A Fine, John H. Harvey (2013). Handbook of Divorce and Relationship Dissolution. Psychology Press. p. 160. ISBN 1317824210. Retrieved December 9, 2014. 
  149. ^ June M. Reinisch, Ruth Beasley (1991). The Kinsey Institute New Report On Sex. Macmillan. p. 74. ISBN 0312063865. Retrieved December 9, 2014. 
  150. ^ Pepper Schwartz, Virginia Rutter (1998). The Gender of Sexuality. Rowman & Littlefield Publishers. p. 129. ISBN 0803990421. Retrieved December 9, 2014. 
  151. ^ William Yarber, Barbara Sayad, Bryan Strong (2012). Human Sexuality: Diversity in Contemporary America: Eighth Edition. McGraw-Hill Higher Education. p. 445. ISBN 0077435257. Retrieved December 9, 2014. 
  152. ^ Beth Montemurro (2014). Deserving Desire: Women's Stories of Sexual Evolution. Rutgers University Press. p. 169. ISBN 0813573068. Retrieved December 9, 2014. 
  153. ^ Michael Gurian (2013). The Wonder of Aging: A New Approach to Embracing Life After Fifty. Simon and Schuster. p. 178. ISBN 1476706719. Retrieved December 9, 2014. 
  154. ^ a b Bryan Strong, Theodore Cohen (2013). The Marriage and Family Experience: Intimate Relationships in a Changing Society. Cengage Learning. p. 212. ISBN 1285531892. Retrieved December 9, 2014. 
  155. ^ a b Ponton, Lynn (2000). The Sex Lives of Teenagers. Dutton Publishing. p. 3. ISBN 978-0-452-28260-5. 
  156. ^ Ralph J. DiClemente, John S. Santelli, Richard A. Crosby (2009). Adolescent Health: Understanding and Preventing Risk Behaviors. John Wiley & Sons. p. 521-522. ISBN 047045279X. Retrieved December 7, 2014. 
  157. ^ a b Jamie L Abaied, Deepika Anand, Tracey L Auster, Daniel BE (2014). The Oxford Handbook of Depression and Comorbidity. Oxford University Press. p. 450. ISBN 0199797005. Retrieved December 7, 2014. 
  158. ^ Kevin Ryan, James Cooper (2008). Those Who Can, Teach. Cengage Learning. p. 110. ISBN 0547204884. Retrieved December 9, 2014. 
  159. ^ "Peer rejection tied to early sex in pre-teens" (PDF). Issue Update. MedlinePlus. October 2002. Archived from the original on 2007-10-11. Retrieved August 5, 2011. 
  160. ^ R.S.Goya, Indian Institute of Health Management Research, Jaipur, India (2005). "Socio-psychological Constructs of Premarital Sex Behavior among Adolescent Girls in India" (PDF). Abstract. Princeton University. Retrieved August 5, 2011. 
  161. ^ Madsen S., Collins W. A. (2005). Differential predictions of young adult romantic relationships from transitory vs. longer romantic experiences during adolescence. Presented at Biennial Meeting of the Society for Research on Child Development, Atlanta, Georgia.
  162. ^ Seiffge-Krenke I., Lang J. (2002). Forming and maintaining romantic relations from early adolescence to young adulthood: evidence of a developmental sequence. Presented at 19th Biennial Meeting of the Society for Research on Adolescence, New Orleans, Louisiana.
  163. ^ Pearce MJ, Boergers J, Prinstein MJ (2002). "Adolescent obesity, overt and relational peer victimization, and romantic relationships". Obesity Research 10 (5): 386–93. doi:10.1038/oby.2002.53. PMID 12006638. 
  164. ^ Zimmer-Gembeck MJ, Siebenbruner J, Collins WA (2004). "A prospective study of intraindividual and peer influences on adolescents' heterosexual romantic and sexual behavior". Archives of Sexual Behavior 33 (4): 381–394. doi:10.1023/B:ASEB.0000028891.16654.2c. PMID 15162084. 
  165. ^ William N. Eskridge Jr. Dishonorable Passions: Sodomy Laws in America, 1861–2003. (2008) Viking Adult. ISBN 0-670-01862-7
  166. ^ Noelle N. R. Quenivet. Sexual Offenses in Armed Conflict & International Law. (2005) Hotei Publishing. ISBN 1-57105-341-7
  167. ^ Marshall Cavendish Corporation (2010). Sex and Society. Marshall Cavendish Corporation. pp. 143–144. ISBN 0-7614-7906-6. Retrieved August 25, 2013. 
  168. ^ a b Jerrold S. Greenberg, Clint E. Bruess, Sarah C. Conklin (2010). Exploring the Dimensions of Human Sexuality. Jones & Bartlett Learning. p. 515. ISBN 0-7637-7660-2. Retrieved August 25, 2013. 
  169. ^ Karen L. Kinnear (2007). Childhood Sexual Abuse: A Reference Handbook. ABC-CLIO. p. 89. ISBN 1-85109-905-0. Retrieved August 25, 2013. 
  170. ^ Reed, E. J. (1997). "Criminal Law and the Capacity of Mentally Retarded Persons to Consent to Sexual Activity". Virginia Law Review 83 (4): 799–827. doi:10.2307/1073749. JSTOR 1073749. 
  171. ^ a b Robert T. Francoeur, Raymond J. Noonan, Beldina Opiyo-Omolo (2004). The Continuum Complete International Encyclopedia of Sexuality. Continuum International Publishing Group. p. 173. ISBN 0826414885. Retrieved April 30, 2013. 
  172. ^ Diagnostic and Statistical Manual of Mental Disorders: DSM-IV. Washington, DC: American Psychiatric Association. 2000. ISBN 0-89042-025-4. 
  173. ^ Milner, JS; Dopke CA (2008). "Paraphilia Not Otherwise Specified: Psychopathology and theory". In Laws DR & O'Donohue WT. Sexual Deviance, Second Edition: Theory, Assessment, and Treatment. New York: The Guilford Press. pp. 384–418. ISBN 1-59385-605-9. 
  174. ^ Seto, MC; Barbaree HE (2000). "Paraphilias". In Hersen M; Van Hasselt VB. Aggression and violence: an introductory text. Boston: Allyn & Bacon. pp. 198–213. ISBN 0-205-26721-1. 
  175. ^ Abigail Perdue, Randall Lockwood (2014). Animal Cruelty and Freedom of Speech: When Worlds Collide. Purdue University Press. pp. 6–8. ISBN 1557536333. Retrieved December 9, 2014. 
  176. ^ "Blanchflower v. Blanchflower and Mayer". Gay & Lesbian Advocates & Defenders (GLAD). December 31, 2003. Retrieved August 9, 2013. 
  177. ^ "IN THE MATTER OF DAVID G. BLANCHFLOWER AND SIAN E. BLANCHFLOWER". New Hampshire Judicial Branch/courts.state.nh.us. November 7, 2003. Retrieved August 9, 2013. 
  178. ^ Janet Afary. Sexual Politics in Modern Iran. (2009) Cambridge University Press. ISBN 0-521-89846-3
  179. ^ a b Daniel L. Akin (2003). God on Sex: The Creator's Ideas About Love, Intimacy, and Marriage. B&H Publishing Group. pp. 291 pages. ISBN 0805425969. 
  180. ^ a b c Dennis P. Hollinger (2009). The Meaning of Sex: Christian Ethics and the Moral Life. Baker Academic. p. 30-33. ISBN 0801035716. Retrieved December 9, 2014. 
  181. ^ Chad Denton (2014). The War on Sex: Western Repression from the Torah to Victoria. McFarland. pp. 107–117. ISBN 0547204884. Retrieved December 9, 2014. 
  182. ^ a b Margaret D. Kamitsuka (2010). The Embrace of Eros: Bodies, Desires, and Sexuality in Christianity. Fortress Press. pp. 16–17. ISBN 1451413513. Retrieved December 9, 2014. 
  183. ^ Stefanie Knauss (2014). More Than a Provocation: Sexuality, Media and Theology. Vandenhoeck & Ruprecht. p. 69. ISBN 3525604505. Retrieved December 9, 2014. 
  184. ^ Robert G. Barnes, Rosemary J. Barnes (1996). Great Sexpectations: Finding Lasting Intimacy in Your Marriage. Zondervan. p. 66. ISBN 0310201373. Retrieved December 9, 2014. 
  185. ^ a b Christo Scheepers (2012). Between the Covers: Sexual freedom through the bond of marriage. Struik Christian Media. p. 53. ISBN 141532056X. Retrieved December 9, 2014. 
  186. ^ William H. Swatos, Peter Kivisto (1998). Encyclopedia of Religion and Society. Rowman Altamira. p. 464. ISBN 0761989560. Retrieved December 9, 2014. 
  187. ^ Laura J. Zilney, Lisa Anne Zilney (2009). Perverts and Predators: The Making of Sexual Offending Laws. Rowman & Littlefield Publishers. pp. 7–8. ISBN 0742566242. Retrieved December 9, 2014. 
  188. ^ a b Don S. Browning, Martha Christian Green, John Witte. Sex, marriage, and family in world religions. (2006) Columbia University Press. ISBN 0-231-13116-X [1]
  189. ^ Abdul Rahman bin Abdul Karim al-Sheha. Islamic Perspective of Sex (2003) Saudi Arabia. ISBN 9960-43-140-1
  190. ^ Fatima M. D'Oyen. The Miracle of Life. (2007) Islamic Foundation (UK). ISBN 0-86037-355-X
  191. ^ Thompson, Lady Gwen; Wiccan-Pagan Potpourri; Green Egg, №69; Ostara 1974
  192. ^ Hans Holzer. The Truth about Witchcraft (1971) Doubleday. page 128. ISBN 0-09-004860-1
  193. ^ Kenneth E. Bowers. God Speaks Again: An Introduction to the Baha'i Faith. (2004) Baha'i Publishing. ISBN 1-931847-12-6
  194. ^ John A. Buehrens and Forrest Church. A Chosen Faith: An Introduction to Unitarian Universalism. (1998) Beacon Press. ISBN 0-8070-1617-9
  195. ^ Hodgkinson, Liz (2002). Peace and Purity: The Story of the Brahma Kumaris a Spiritual Revolution. HCI. pp. 2–29. ISBN 1-55874-962-4. 
  196. ^ Babb, Lawrence A. (1987). Redemptive Encounters: Three Modern Styles in the Hindu Tradition (Comparative Studies in Religion and Society). Oxford University Press. ISBN 0-7069-2563-7. "Sexual intercourse is unnecessary for reproduction because the souls that enter the world during the first half of the Cycle are in possession of a special yogic power (yog bal) by which they conceive children"
  197. ^ Barrett, David V (2001). The New Believers. Cassell & Co. pp. 265. ISBN 0-304-35592-5.
  198. ^ Chase, Stacey (July 23, 2006). "The Last Ones Standing". The Boston Globe. 
  199. ^ William Skudlarek. Demythologizing Celibacy: Practical Wisdom from Christian and Buddhist Monasticism. (2008) Liturgical Press. ISBN 0-8146-2947-4
  200. ^ Naomi R. Cahn, June Carbone (2010). Red families v. blue families: legal polarization and the creation of culture. Oxford University Press US. p. 129. ISBN 0-19-537217-4. Retrieved July 29, 2011. 
  201. ^ Donald J. Cantor (2006). Same-sex marriage: the legal and psychological evolution in America. Wesleyan University Press. pp. 191 pages. ISBN 0-8195-6812-0. Retrieved July 29, 2011. 
  202. ^ American Psychological Association (2004). "Resolution on Sexual Orientation and Marriage". Retrieved July 29, 2011. 
  203. ^ American Psychiatric Association (2005). "Support of Legal Recognition of Same-Sex Civil Marriage". Retrieved July 29, 2011. 
  204. ^ Taylor, Pamela K. (July 31, 2009). "Marriage: Both Civil and Religious". The Washington Post. Retrieved July 28, 2011. 
  205. ^ K. Smith, Susan (July 30, 2009). "Marriage a Civil Right, not Sacred Rite". The Washington Post. Retrieved July 28, 2011. 
  206. ^ "Decision in Perry v. Schwarzenegger". ecf.cand.uscourts.gov. July 31, 2009. Retrieved July 28, 2011. 
  207. ^ Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). "Chelicerata: Araneae". Invertebrate Zoology (7 ed.). Brooks/Cole. pp. 571–584. ISBN 0-03-025982-7. 
  208. ^ Edward J. Denecke, Jr. (2006). New York State Grade 8 Intermediate Level Science Test. Barron's Educational Series. p. 105. ISBN 0764134337. Retrieved December 9, 2014. 
  209. ^ M. Yadav (2003). Breeding in Insects. Discovery Publishing House. p. 59. ISBN 817141737X. Retrieved December 9, 2014. 
  210. ^ Franz Engelmann (2013). The Physiology of Insect Reproduction: International Series of Monographs in Pure and Applied Biology: Zoology. Elsevier. pp. 58–59. ISBN 1483186539. Retrieved December 9, 2014. 
  211. ^ Janet Leonard, Alex Cordoba-Aguilar (2010). The Evolution of Primary Sexual Characters in Animals. Oxford University Press. p. 334. ISBN 0199717036. Retrieved December 9, 2014. 
  212. ^ P. J. Gullan, P. S. Cranston (2009). The Insects: An Outline of Entomology. John Wiley & Sons. p. 124. ISBN 1405144572. Retrieved December 9, 2014. 

External links