While vaginal births after caesarean (VBAC) are not uncommon today, the rate of VBAC has declined to include less than 10% of births after previous caesarean in the USA. [ 17 ] [ 18 ]  Although caesarean deliveries made up only 5% of births overall in the USA until the mid-1970s, it was commonly believed that for women with previous caesarean sections, "Once a Caesarean, always a Caesarean". A consumer-driven movement supporting VBAC changed medical practice and led to soaring rates of VBAC in the 1980s and early 1990s, but rates of VBAC dramatically dropped after the publication of a highly publicized scientific study showing worse outcomes for VBACs as compared to repeat caesarean and the resulting medicolegal changes within obstetrics. [ 19 ]  In 2010, the National Institutes of Health, U.S. Department of Health and Human Services, and American Congress of Obstetrics and Gynecology all released statements in support of increasing VBAC access and rates. [ 5 ] [ 20 ] [ 7 ]


Although caesarean sections made up only 5% of all deliveries in the early 1970s, [ 21 ]  among women who did have primary caesarean sections, the century-old opinion held, "Once a caesarean, always a caesarean." Overall, cesarean sections became so commonplace that the caesarean delivery rate climbed to over 31% in 2006. [ 4 ]   A mother-driven movement supporting VBAC changed standard medical practice, and rates of VBAC rose in the 1980s and early 1990s. However, a major turning point occurred in 1996 when one well publicized study in  The New England Journal of Medicine  reported that vaginal delivery after previous caesarean section resulted in more  maternal complications  than a repeat caesarean delivery. [ 19 ]  The American Congress of Obstetrics and Gynecology subsequently issued guidelines which identified VBAC as a high-risk delivery requiring the availability of an  anesthesiologist , an  obstetrician , and an operating room on standby. [ 22 ]  Logistical and legal (professional liability) concerns led many hospitals to enact overt or de facto VBAC bans. As a result, the rate at which VBAC was attempted fell from 26% in the early 1990s to 8.5% in 2006. [ 4 ]


In March 2010, the  National Institutes of Health  met to consolidate and discuss the overall up-to-date body of VBAC scientific data and concluded, "Given the available evidence, trial of labor is a reasonable option for many pregnant women with one prior low transverse uterine incision." [ 5 ]  Simultaneously, the U.S. Department of Health and Human Services  Agency for Healthcare Research and Quality  reported that VBAC is a reasonable and safe choice for the majority of women with prior caesarean and that there is emerging evidence of serious harms relating to multiple caesareans. [ 14 ]  In July 2010, The  American Congress of Obstetricians and Gynecologists  (ACOG) similarly revised their own guidelines to be less restrictive of VBAC, stating, "Attempting a vaginal birth after cesarean (VBAC) is a safe and appropriate choice for most women who have had a prior cesarean delivery, including for some women who have had two previous cesareans." [ 20 ]  and this is also the current position of the Royal College of Obstetricians and Gynaecologists in the UK.


Enhanced access to VBAC has been recommended based on the most recent scientific data on the safety of VBAC as compared to repeat caesarean section, including the following recommendation emerging from the NIH VBAC conference panel in March 2010, "We recommend that hospitals, maternity care providers, health care and professional liability insurers, consumers, and policymakers collaborate on the development of integrated services that could mitigate or even eliminate current barriers to trial of labor." [ 5 ]  The U.S Department of Health and Human Services'  Healthy People 2020  initiative includes objectives to reduce the primary caesarean rate and to increase the VBAC rate by at least 10% each. [ 23 ]


The  American Congress of Obstetricians and Gynecologists  (ACOG) modified the guidelines on vaginal birth after previous Caesarean delivery in 1999, 2004, and again in 2010. [ 11 ]  In 2004, this modification to the guideline included the addition of the following recommendation:


Because uterine rupture may be catastrophic, VBAC should be attempted in institutions equipped to respond to emergencies with physicians immediately available to provide emergency care. [ 11 ]


In 2010, ACOG modified these guidelines again to express more encouragement of VBAC, but maintained it should still be undertaken at facilities capable of emergency care, though patient autonomy in assuming increased levels of risk should be respected. [ 4 ]


The recommendation for access to emergency care during trial of labor has, in some cases, had a major impact on the availability of VBACs to birthing mothers in the US. For example, a study of the change in frequency of VBAC deliveries in California after the change in guidelines, published in 2006, found the VBAC rate fell to 13.5% after the change, compared with 24% VBAC rate before the change. [ 24 ]  The new recommendation has been interpreted by many hospitals as indicating a full surgical team must be standing by to perform a Caesarean section for the full duration of a VBAC woman's labor. Hospitals that prohibit VBACs entirely are said to have a 'VBAC ban'. In these situations, birthing mothers are forced to choose between having a repeat Caesarean section, finding an alternate hospital in which to deliver their babies or attempting delivery outside the hospital setting. [ 25 ]


Most recently, enhanced access to VBAC has been recommended based on updated scientific data on the safety of VBAC as compared to repeat caesarean section, including the following recommendation emerging from the NIH VBAC conference panel in March 2010, "We recommend that hospitals, maternity care providers, health care and professional liability insurers, consumers, and policymakers collaborate on the development of integrated services that could mitigate or even eliminate current barriers to trial of labor." [ 5 ]  The U.S Department of Health and Human Services' Healthy People 2020 initiative includes objectives to reduce the primary cesarean rate and to increase the VBAC rate by at least 10% each. [ 7 ]


ACOG recommends that obstetricians offer most women with one prior cesarean section with a low-transverse incision a trial of labor ( TOLAC ) and that obstetricians should discuss the risks and benefits of VBAC with these patients. [ 4 ]


Pemberton v. Tallahassee Memorial Regional Center , 66 F. Supp. 2d 1247 (N.D. Fla. 1999), is a case in the  United States  regarding  reproductive rights . Pemberton had a previous Caesarean section (vertical incision), and with her second child attempted to have a VBAC. [ 26 ]  When a doctor she had approached about a related issue at the  Tallahassee Memorial Regional Center  found out, he and the hospital sued to force her to get a c-section. The court held that the rights of the fetus at or near birth outweighed the rights of Pemberton to determine her own medical care. [ 27 ] [ 28 ]  She was physically forced to stop laboring, and taken to the hospital, where a c-section was performed. [ 26 ]  Her suit against the hospital was dismissed. [ 26 ]   The court held that a cesarean section at the end of a full-term pregnancy was here deemed to be medically necessary by doctors to avoid a substantial risk that the fetus would die during delivery due to uterine rupture, a risk of 4–6% according to the hospital's doctors and 2% according to Pemberton's doctors. Furthermore, the court held that a state's interest in preserving the life of an unborn child outweighed the mother's constitutional interest of bodily integrity. [ 29 ]  The court held that  Roe v. Wade  was not applicable, because bearing an unwanted child is a greater intrusion on the mother's constitutional interests than undergoing a cesarean section to deliver a child that the mother affirmatively desires to deliver. The court further distinguished  In re A.C.  by stating that it left open the possibility that a non-consenting patient's interest would yield to a more compelling countervailing interest in an "extremely rare and truly exceptional case." The court then held this case to be such. [ 26 ] [ 30 ]


VBAC, compared to vaginal birth without a history of Caesarean section, confers an increased risks for  placenta previa ,  placenta accreta , prolonged labor,  antepartum hemorrhage ,  uterine rupture ,  preterm birth ,  low birth weight , and  stillbirth . However, some risks may be due to confounding factors related to the indication for the first caesarean, rather than due to the procedure itself. [ 31 ]


A  vaginal delivery  is the  birth  of  offspring  in  mammals  ( babies  in humans) through the  vagina  (also called the "birth canal"). [ 1 ]  It is the most common method of  childbirth  worldwide. [ 2 ]  It is considered the preferred method of delivery, as it is correlated with lower  morbidity  and  mortality  than  caesarean sections  (C-sections), [ 3 ]  though it is not clear whether this is causal. [ 4 ]


70% of births in the United States in 2019 were vaginal deliveries. [ 5 ]


80% of births globally in 2021 were vaginal deliveries, with rates varying from 95% in sub-Saharan Africa to 45% in the Caribbean. [ 2 ]


Benefits for the mother include


Benefits for the infant include:


Different types of vaginal deliveries have different terms:


Labor is characterized by uterine contractions which push the fetus through the  birth canal  and results in delivery. [ 14 ]  Labor is divided into three stages.


Complications of vaginal delivery can be grouped into the following criteria; failure to progress, abnormal fetal heart rate tracing, intrapartum hemorrhage, and post-partum hemorrhage.


Failure to progress  occurs when the labor process slows or stops entirely, indicated by slowed cervical dilation. [ 3 ]  Factors that place a woman's pregnancy at higher risk include advanced maternal age, Premature Rupture of Membranes ( PROM ) and induction of labor. [ 17 ]  Pitocin, a synthetic version of oxytocin, is often administered to induce labour. Oxytocin is a natural hormone and a  uterotonic agent  which stimulates the uterine muscles to contract and initiate labour.  [ 18 ]  Cesarean section is also commonly considered when the pregnancy fails to progress. [ 19 ]


Abnormal fetal heart tracing  suggests that the fetus's heart rate has slowed during labor due to head compression, cord compression,  hypoxemia  or anemia. [ 3 ]   Uterine tachysystole , the most common adverse effect of oxytocin (usually as a result of a problematic dosage), can result in nonreassuring fetal heart tracing. It can usually be reversed when oxytocin infusion is decreased or stopped. [ 20 ]  If the abnormal fetal heart rate persists, and uterine tachysystole continues,  tocolytic  remedies, such as  terbutaline , may be used. Afterward, if beneficial and uterine tone has returned to baseline and fetal status is stable, oxytocin as a labor augmenting agent may be resumed. [ 21 ]  The persistence of an abnormal fetal heart rate may also indicate that a cesarean section is necessary. [ 22 ]


Intrapartum hemorrhage  is characterized by the presence of copious blood during labor. The bleeding may be due to placental abruption, uterine rupture, placenta accrete, undiagnosed placenta previa, or vasa previa. [ 3 ]  Cesarean section is indicated.


Post-partum hemorrhage  is defined by the loss of at least 1,000 mL of blood accompanied with symptoms of  hypovolemia  within 24 hours after delivery. Typically, the first symptom is excessive bleeding accompanied by  tachycardia . Significant loss of blood may also result in  hypotension , nausea,  dyspnea , and chest pain. [ 23 ]  It is estimated that between 3% and 5% of women giving birth vaginally will experience post-partum hemorrhage. Risk factors include  fetal macrosomia ,  pre-eclampsia , and prolonged labor. [ 23 ]  Prevention consists of administering oxytocin ( Pitocin ) at delivery and early umbilical cord clamping. [ 24 ]  Post-partum hemorrhage is usually attributed to uterus atony, when the uterus fails to contract after delivering the baby. [ 25 ]


As a result of discrepancies in diagnostic criteria and  human variability , there is wide variation in data on maternal and fetal death associated with poor progress. [ 19 ]


More than 1 in 10 women with assisted vaginal births develop an infection. [ 26 ]  Preventive  antibiotics  are recommended to women who have had an assisted vaginal birth by the  World Health Organization . [ 27 ]  An analysis has showed that preventive antibiotics reduce the risk of infection after an assisted vaginal birth, irrespective of whether a woman has had a  perineal tear , an  episiotomy , or both. Delays in receiving antibiotics also increases the risk of infection. [ 28 ] [ 29 ]


Spontaneous vaginal delivery at term is the preferred outcome of pregnancy, and according to the International Federation of Gynecology and Obstetrics, will be recommended if there are no evidence-based clinical indications for  Cesarean section . [ 30 ]  However, there are some contraindications for vaginal delivery that would result in conversion to Cesarean delivery. The decision to switch to Cesarean delivery is made by the health care provider and mother and is sometimes delayed until the mother is in labor.


Breech birth  presentations occur when the fetus's buttocks or lower extremities are poised to deliver before the fetus's upper extremities or head. The three types of breech positions are footling breech, frank breech, and complete breech. These births occur in 3% to 4% of all term pregnancies. [ 31 ]  They usually result in Cesarean sections because it is more difficult to deliver the baby through the birth canal and there is a lack of expertise in vaginal breech delivery and therefore fewer vaginal breech deliveries performed. It is also associated with cord prolapse and an elevated risk for birth defects in breech babies. [ 31 ]  Controversy and debate surround the topic due to different views on the preferred route of delivery when breech presentation occurs. [ 31 ] [ 32 ]  Some health professionals believe that vaginal breech delivery can be a safe alternative to planned Cesarean in certain instances. [ 31 ]


Complete  placenta previa  occurs when the placenta covers the opening of the cervix. If placenta previa is present at the time of delivery, vaginal delivery is contraindicated because the placenta is blocking the fetus's passageway to the vaginal canal.


Herpes simplex virus  with active genital lesions or prodromal symptoms  is a contraindication for vaginal delivery so as to avoid mother-fetal transfer of HSV lesions.


Untreated human immunodeficiency virus ( HIV ) infection  is a contraindication for vaginal delivery to avoid mother-fetal transfer of human immunodeficiency virus. [ 33 ]


The  Human Microbiome Project (HMP) , completed in 2012, laid the foundation for further investigation into the role the microbiome plays in overall health and disease. One area of particular interest is the role which delivery mode plays in the development of the infant/neonate microbiome and what potential implications this may have long term. It has been found that infants born via vaginal delivery have microbiomes closely mirroring that of the mother's vaginal microbiome, whereas those born via cesarean section tend to resemble that of the mother's skin. [ 1 ]  One notable study from 2010 illustrated an abundance of  Lactobacillus  and other typical vaginal genera in stool samples of infants born via vaginal delivery and an abundance of  Staphylococcus  and  Corynebacterium,  commonly found on the skin surfaces, in stool samples of infants born via cesarean section. [ 2 ]  From these discoveries came the concept of  vaginal seeding,  also known as  microbirthing , [ 3 ]  which is a procedure whereby  vaginal  fluids (and hence vaginal  microbes ) are applied to a new-born child delivered by  caesarean section . The idea of vaginal seeding was explored in 2015 after Maria Gloria Dominguez-Bello discovered that birth by caesarean section significantly altered the newborn child's  microbiome  compared to that of natural birth. [ 4 ]  The purpose of the technique is to recreate the natural transfer of bacteria that the baby gets during a  vaginal birth . It involves placing swabs in the mother's  vagina , and then wiping them onto the baby's face, mouth, eyes and skin. [ 5 ]  Due to the long-drawn nature of studying the impact of vaginal seeding, there are a limited number of studies available that support or refute its use. [ 6 ]  The evidence suggests that applying microbes from the mother's vaginal canal to the baby after cesarean section may aid in the partial restoration of the infant's natural  gut microbiome  with an increased likelihood of pathogenic infection to the child via vertical transmission. [ 7 ] [ 8 ]


Theodor Rosebury  began his study of the human microbiota in 1928. More than thirty years later, he published  Microorganisms Indigenous to Man . In this book, he discussed the importance of microbial colonization after birth and its role in forming the infant microbiome. [ 9 ]  In 2015, Rosebery's perspective of microbial colonization after birth was further elucidated by a group of researchers in the United States. Studies performed by Maria Gloria Dominguez-Bello and her team indicated that the microbiome of a child born by cesarean section was significantly different from that of a child delivered by natural birth. [ 4 ]  It has been found that infants born via cesarean section lack bacteroide species until 6-18. Interestingly, a study performed at Mass General Hospital published in 2020 found no significant difference in bacteroide species colonization between pre-labor c-sections and post-labor c-sections, indicating that vaginal exposure may not be the sole driving force for bacteroides colonization. [ 10 ]


Given that the vaginal microbiome is thought to be influential in the development of the neonatal microbiome, it is important to understand and acknowledge its complexity. Early studies into the vaginal microbiome revealed a predominance of  Lactobacillus  species. Similarly, a 2021 study evaluating impacts of the maternal vaginal microbiome composition on the development of the infant gut microbiome in early life found that the vaginal microbiome of the pregnant participants was dominated by one of several species of  Lactobacillus , with four species appearing most common. [ 2 ]


Around 1914 the association between anaerobic cocci and abnormal vaginal discharge was first established. Later, in 1955,  Gardnerella vaginalis  was identified as a causative agent for bacterial vaginosis (BV). This was further complicated in the 1990s when several other species were discovered from anaerobic cultures from individuals with symptoms corresponding to BV. One commonality remained throughout those experiencing symptoms of BV; The depletion of lactic acid producing bacterial species. The presence of BV has been subsequently linked to preterm birth as well as increased risk for development of sexually transmitted disease which is thought to be linked to the deficiency of  Lactobacillus  species, as they produce lactic acid and H 2 O 2  which is thought to have protective properties against some pathogenic bacteria/viruses. [ 11 ]  Another interesting component of the vaginal microbiome comes with its stability and variability over time. A 2012 study published in S cience Translational Medicine  investigated the temporal dynamics of the vaginal microbiota and found that the stability of the vaginal microbiome over time was highly individual. Some of the participants tended to exhibit higher variability over the course of the 16 weeks study with up to three alterations in their vaginal microbiome during that time. In contrast, others exhibited almost complete stability throughout the course of the study. [ 12 ]


Fluctuations in the vaginal microbiome have been demonstrated with the menstrual cycle and intercourse. Fluctuations brought on during pregnancy have also been an area of interest as nearly all organ systems change during pregnancy to promote and maintain the pregnancy. It is known that  pregnancy results in thickening of the vaginal mucosa and an increase in cervical secretions which in turn leads to smooth muscle cell hypertrophy and relaxation of the connective tissue. In addition, vaginal epithelium also exhibits hypertrophy which subsequently leads to crowding of the epithelial cells which themselves are rich in glycogen. Throughout the duration of gestation, the rising estrogen leads to additional increases in glycogen which is then metabolized into lactic acid which causes the vagina to become more acidic. This in turn causes an increase in  Lactobacillus  growth in the vagina. Interestingly, a 2009 study of longitudinal analysis of the vaginal microflora in pregnancy found that 56.5% of participants who initially had lactobacilli-diminished vaginal microbiomes during the first trimester of pregnancy developed a prevalence of the lactobacilli later in pregnancy, hinting towards the importance this genus may play in a neonate. [ 13 ]


In the early life of animals, as well as humans, the development of the immune system and metabolism is influenced by the infant's microbiota, and alteration,  dysbiosis , in the microbiota can either prevent or cause disease. [ 14 ] [ 15 ]  The method of birth, whether vaginal or caesarean section, determines the exposure and colonization of the infant's gut microbiota. The purpose behind the practice of vaginal seeding or micro birthing is that it allows an infant delivered via caesarean section to come in contact with microbes from the birth canal. Infants delivered vaginally are exposed to beneficial  microorganisms  known as  microbiota  when they travel down the  birth canal . Infants are exposed to critical bacteria via vaginal birth, such as Lactobacillus,  Prevotella ,  Bacteroides ,  Escherichia / Shigella , and  Bifidobacterium . Bifidobacterium is a key bacteria in the nourishment of the infants, development of immunity, and maturation of the intestinal tissue. [ 16 ]  The expectation is that this may boost their gut bacteria and lessen the danger of health issues normally associated with caesarian infants. It contributes to the seeding of the infant's  gut. [ 17 ]


The baby is exposed to the mother's vaginal microbes that wash over the child in the birth canal, which coves the skin, and enters the baby's eyes, ears, nose, and mouth. These microbes often travel down into the gut after being swallowed. It is said that these microbes are important in the  postnatal development  of the immune system of the baby. [ 18 ]


In the event that a  C-section  is done before labour starts or before a woman's water breaks, the infant will not come into contact with maternal vaginal fluid or bacteria. Instead, they come in contact with skin microbes, such as  Staphylococcus ,  Streptococcus ,  Veillonella , and  Corynebacterium . [ 6 ]  a very different set of species. [ 19 ]  These differences, in turn, have been associated with increased risks of  asthma ,  allergies ,  obesity , and  immune deficiencies . Thus, these differences appear more often in infants after a  caesarean delivery  than after a vaginal delivery, according to certain epidemiological data. [ 20 ]  In fact, in the United States, studies have found that 64-82% of neonatal cases of methicillin-resistant Staphylococcus aureus infections of the skin were found to occur in those born via C-section. [ 1 ]


Evidence suggests that cesarean delivery can increase the risk for inflammatory and metabolic diseases in infants. [ 8 ]  It is unclear whether vaginal seeding has long-term benefits or whether it is safe. In 2016 a small study of 18 infants was published in the Journal Nature Medicine to look into the benefits of vaginal seeding. The microbiome of the four cesarean delivered infants receiving the microbial transfer was found to have a similar microbiome to the seven vaginally delivered infants. [ 7 ]  The results of the study suggest that vaginal seeding partially restores the neonatal microbiome. [ 7 ]  However, the study authors acknowledged that the long-term consequences of vaginal seeding remain unclear due to limited data.


In 2017, a subsequent study was published which found that there was not a big difference, after six weeks, between the microbes of infants born vaginally versus those who delivered by C-section without receiving vaginal seeding. [ 21 ]   Certain scholars have pointed out that a baby's exposure to bacteria begins even before birth and more research is required on this matter. [ 22 ]


The scientific evidence regarding the short and long-term benefits of vaginal seeding, as well as the risks involved, is limited. Due to the widespread clinical advice given against performing vaginal seeding, there is insufficient support for the procedure. [ 23 ]  Following a nonclinical vaginal seeding procedure, there was a reported case of localized neonatal herpes simplex virus (HSV) infection, however, it cannot be supported that the infection was due to the procedure or another factor. [ 23 ]


Infants delivered by C-section are at a lower danger of exchange of some potentially harmful microbes and infections from the birth canal. Although it remains unknown, vaginal seeding procedures may take these harmful microorganisms, including undetected sexually transmitted infections (STIs) and unintentionally transfer them to the infant. This could potentially cause an  infection . [ 19 ]  It has been proposed that implementing a screening protocol for potential vaginal pathogens may be beneficial when considering vaginal seeding. [ 24 ]


An editorial written in the  British Medical Journal  is advising practitioners and parents to not perform vaginal seeding as there is not enough evidence that it is beneficial for infants and could potentially put babies' health at risk. [ 25 ]


The American College of Obstetricians and Gynecologists  (ACOG) also does not encourage or recommend vaginal seeding due to lack of evidence. [ 26 ]


Currently, the establishment of the infant microbiome including what influences are associated with optimal versus dysbiotic outcomes remains as a key component of health research. As of late, there have been only few studies evaluating the potential relationship between the maternal vaginal microbiome and the gut microbiome of the infant from the species or strain level. In context of the bacterial baptism hypothesis, this is essential, as merely reporting a genre (such as Lactobacillus) would fail to provide insight for the assessment of vertical transmission. [ 1 ]  Presence or absence of certain species within the same genre may greatly alter functionality, making further investigation into the implication of specie variation an important component of both further research of the vaginal microbiome and development of the infant microbiome. Additionally, maternal alterations in the intestinal microbiome during pregnancy may also play a role in the microbial colonization of vaginally delivered infants. When comparing stool samples from first and third trimester women, a 2012 study,  Host remodeling of the gut microbiome and metabolic changes during pregnancy,  discovered there is an increase in Proteobacteria as pregnancy progresses. [ 27 ]  Given the potential maternal fecal contamination that is prone to occur during vaginal delivery, it is important to consider how alterations in the intestinal microbiome during pregnancy may influence microbial colonization of the infant. Furthermore, examination of the intestinal microbiome of infants born via cesarean versus vaginal delivery have revealed differences in colonization between the two groups however, further studies have suggested that the bacterial enzymes were not altered in the stool of these infants between the two delivery modes, making it unclear whether the type of microbe or the enzymatic activities and byproducts it produces are more important for the infant. [ 28 ]


Human sexuality  is the way people experience and express themselves  sexually . [ 1 ] [ 2 ]  This involves  biological ,  psychological ,  physical ,  erotic ,  emotional ,  social , or  spiritual  feelings and behaviors. [ 3 ] [ 4 ]  Because it is a broad term, which has varied with historical contexts over time, it lacks a precise definition. [ 4 ]  The biological and physical aspects of sexuality largely concern the  human reproductive functions , including the  human sexual response cycle . [ 3 ] [ 4 ]


Someone's  sexual orientation  is their pattern of sexual interest in the opposite and/or same sex. [ 5 ]  Physical and emotional aspects of sexuality include bonds between individuals that are expressed through profound feelings or physical manifestations of  love , trust, and care. Social aspects deal with the effects of human society on one's sexuality, while spirituality concerns an individual's spiritual connection with others. Sexuality also affects and is affected by cultural, political, legal, philosophical,  moral ,  ethical , and religious aspects of life. [ 3 ] [ 4 ]


Interest in sexual activity normally increases when an individual reaches  puberty . [ 6 ]  Although no single theory on the cause of sexual orientation has yet gained widespread support, there is considerably more evidence supporting nonsocial causes of sexual orientation than social ones, especially for males. Hypothesized social causes are supported by only weak evidence, distorted by numerous confounding factors. [ 7 ]  This is further supported by cross-cultural evidence because cultures that are tolerant of  homosexuality  do not have significantly higher rates of it. [ 8 ] [ 9 ]


Evolutionary perspectives on human coupling, reproduction and  reproduction strategies , and  social learning theory  provide further views of sexuality. [ 10 ]  Sociocultural aspects of sexuality include  historical developments  and  religious beliefs . Some cultures have been described as  sexually repressive . The study of sexuality also includes human identity within social groups,  sexually transmitted infections  (STIs), and  birth control  methods.


There is considerably more evidence supporting innate causes of sexual orientation than learned ones, especially for males. This evidence includes the cross-cultural correlation of homosexuality and childhood  gender nonconformity , moderate genetic influences found in  twin studies , evidence for prenatal hormonal effects on brain organization, the  fraternal birth order effect , and the finding that in rare cases where infant males were raised as girls due to physical differences or deformity, they nevertheless turned out attracted to females. Hypothesized social causes are supported by only weak evidence, distorted by numerous confounding factors. [ 7 ]


Cross-cultural evidence also leans more toward non-social causes. Cultures that are very tolerant of homosexuality do not have significantly higher rates of it. Homosexual behavior is relatively common among boys in British single-sex boarding schools, but adult Britons who attended such schools are no more likely to engage in homosexual behavior than those who did not. In an extreme case, the  Sambia people  ritually require their boys to engage in homosexual behavior during adolescence before they have any access to females, yet most of these boys become heterosexual. [ 8 ] [ 9 ]


It is not fully understood why genes causing homosexuality persist in the gene pool. One hypothesis involves  kin selection , suggesting that homosexuals invest heavily enough in their relatives to offset the cost of not reproducing as much directly. This has not been supported by studies in Western cultures, but several studies in  Samoa  have found some support for this hypothesis. Another hypothesis involves  sexually antagonistic  genes, which cause homosexuality when expressed in males but increase reproduction when expressed in females. Studies in both Western and non-Western cultures have found support for this hypothesis. [ 7 ] [ 11 ]


Psychological theories exist regarding the development and expression of gender differences in human sexuality. A number of them (including  neo-analytic  theories,  sociobiological  theories, social learning theory,  social role theory , and  script theory ) agree in predicting that men should be more approving of casual sex (sex happening outside a stable, committed relationship such as  marriage ) and should also be more  promiscuous  (have a higher number of sexual partners) than women. These theories are mostly consistent with observed differences in males' and females' attitudes toward casual sex before marriage in the United States. Other aspects of human sexuality, such as sexual satisfaction, incidence of  oral sex , and attitudes toward  homosexuality  and  masturbation , show little to no observed difference between males and females. Observed gender differences regarding the number of sexual partners are modest, with males tending to have slightly more than females. [ 12 ]


Like other  mammals , humans are primarily grouped into either the  male  or  female  sex. [ 13 ]


The biological aspects of human sexuality deal with the reproductive system, the sexual response cycle, and the factors that affect these aspects. They also deal with the influence of biological factors on other aspects of sexuality, such as organic and neurological responses, [ 14 ]  heredity, hormonal issues, gender issues, and sexual dysfunction. [ 15 ] [ page needed ]


Males and females are anatomically similar; this extends to some degree to the  development of the reproductive system . As adults, they have different reproductive mechanisms that enable them to perform sexual acts and to reproduce. Men and women react similarly to sexual stimuli with minor differences. Women have a monthly reproductive cycle, whereas the male sperm production cycle is more continuous. [ 16 ] [ 17 ] [ 18 ]


The  hypothalamus  is the most important part of the brain for sexual functioning. This is a small area at the base of the brain consisting of several groups of nerve cell bodies that receive input from the  limbic system . Studies have shown that within lab animals, the destruction of certain areas of the hypothalamus causes the elimination of sexual behavior. [ 16 ]  The hypothalamus is important because of its relationship to the  pituitary gland , which lies beneath it. The pituitary gland secretes hormones that are produced in the hypothalamus and itself. The four important sexual hormones are  oxytocin ,  prolactin ,  follicle-stimulating hormone , and  luteinizing hormone . [ 16 ] [ page needed ]


Oxytocin, sometimes referred to as the "love hormone", [ 19 ]  is released in both sexes during sexual intercourse when an  orgasm  is achieved. [ 20 ]  Oxytocin has been suggested as critical to the thoughts and behaviors required to maintain close relationships. [ 19 ] [ 20 ] [ verification needed ]  The hormone is also released in women when they give birth or are breastfeeding. [ 21 ]  Prolactin and oxytocin are responsible for inducing milk production in women. [ 22 ]  Follicle-stimulating hormone (FSH) is responsible for ovulation in women, and acts by triggering egg maturity; in men, it stimulates sperm production. [ 23 ]  Luteinizing hormone (LH) triggers ovulation, which is the release of a mature egg. [ 16 ] [ page needed ]


Males have both internal and external genitalia that are responsible for procreation and sexual intercourse. Production of spermatozoa ( sperm ) is also cyclic, but unlike the female ovulation cycle, the sperm production cycle is constantly producing millions of sperm daily. [ 16 ] [ page needed ]


The external male genitalia are the  penis  and the  scrotum .


The penis provides a passageway for sperm and urine. [ 24 ]  The penis consists of nerves, blood vessels, fibrous tissue, and three parallel cylinders of spongy tissue. [ 25 ]  Other components of the penis include the  shaft ,  glans , root,  cavernous bodies , and  spongy body . [ 25 ]  The three cylindrical bodies of spongy tissue, which are filled with blood vessels, run along the length of the shaft. [ 25 ]  The two bodies that lie side by side in the upper portion of the penis are the corpora cavernosa (cavernous bodies). [ 25 ]  The third, called the corpus spongiosum (spongy body), is a tube that lies centrally beneath the others and expands at the end to form the tip of the penis (glans). [ 25 ]  During  arousal , these bodies  erect  the penis by filling with blood. [ 26 ] [ 27 ] [ 28 ]


The raised rim at the border of the shaft and glans is called the corona. [ 29 ]  The  urethra  connects the urinary bladder to the penis where urine exits the penis through the  urethral meatus . [ 30 ]  The urethra eliminates urine and acts as a channel for semen and sperm to exit the body during sexual intercourse. [ 30 ]  The root consists of the expanded ends of the cavernous bodies, which fan out to form the crura and attach to the pubic bone and the expanded end of the spongy body. [ 31 ]  The bulb of the penis is surrounded by the  bulbospongiosus muscle , while the corpora cavernosa are surrounded by the  ischiocavernosus muscles . [ 32 ]  These aid urination and  ejaculation . [ 33 ]  The penis has a  foreskin  that typically covers the glans; this is sometimes removed by  circumcision  for medical, religious or cultural reasons. In the scrotum, the testicles are held away from the body, one possible reason for this is so sperm can be produced in an environment slightly lower than normal body temperature.


The penis has very little muscular tissue, and this exists in its root. [ 34 ]  The shaft and glans have no muscle fibers. Unlike most other primates, male humans lack a  penile bone . [ 25 ]


Male internal reproductive structures are the  testicles , the duct system, the  prostate  and  seminal vesicles , and the  Cowper's gland . [ 16 ] [ page needed ]


The testicles (male gonads), are where sperm and male hormones are produced. Millions of sperm are produced daily in several hundred seminiferous tubules. Cells called the  Leydig cells  lie between the tubules; these produce hormones called androgens; these consist of  testosterone  and  inhibin . The testicles are held by the spermatic cord, which is a tubelike structure containing blood vessels, nerves, the vas deferens, and a muscle that helps to raise and lower the testicles in response to temperature changes and sexual arousal, in which the testicles are drawn closer to the body. [ 16 ] [ page needed ]


Sperm gets transported through a four-part duct system. The first part of this system is the  epididymis . The testicles converge to form the  seminiferous tubules , coiled tubes at the top and back of each testicle. The second part of the duct system is the  vas deferens , a muscular tube that begins at the lower end of the epididymis. [ 16 ] [ page needed ]  The vas deferens passes upward along the side of the testicles to become part of the spermatic cord. [ 36 ]  The expanded end is the ampulla, which stores sperm before ejaculation. The third part of the duct system is the ejaculatory ducts, which are 1-inch (2.5 cm)-long paired tubes that pass through the prostate gland, where semen is produced. [ 16 ] [ page needed ]  The prostate gland is a solid, chestnut-shaped organ that surrounds the first part of the urethra, which carries urine and semen. [ 16 ] [ page needed ] [ 36 ]  Similar to the female G-spot, the prostate provides sexual stimulation and can lead to orgasm through  anal sex . [ 37 ]


The prostate gland and the seminal vesicles produce seminal fluid that is mixed with sperm to create semen. [ 16 ] [ page needed ]  The prostate gland lies under the bladder and in front of the rectum. It consists of two main zones: the inner zone that produces secretions to keep the lining of the male urethra moist and the outer zone that produces seminal fluids to facilitate the passage of semen. [ 36 ]  The seminal vesicles secrete fructose for sperm activation and mobilization, prostaglandins to cause uterine contractions that aid movement through the uterus, and bases that help neutralize the acidity of the vagina. The Cowper's glands, or bulbourethral glands, are two pea-sized structures beneath the prostate.


The external female genitalia are the  vulva .


The  mons pubis  is a soft layer of fatty tissue overlaying the pubic bone. [ 38 ]  Following puberty, this area grows in size. It has many nerve endings and is sensitive to stimulation. [ 16 ] [ page needed ]


The  labia minora  and  labia majora  are collectively known as the  labia  or "lips". The labia majora are two elongated folds of skin extending from the mons to the  perineum . Its outer surface becomes covered with hair after puberty. In between the labia majora are the labia minora, two hairless folds of skin that meet above the  clitoris  to form the  clitoral hood , which is highly sensitive to touch. The labia minora become engorged with blood during sexual stimulation, causing them to swell and turn red. [ 16 ] [ page needed ]


The labia minora are composed of connective tissues that are richly supplied with blood vessels which cause a pinkish appearance. Near the anus, the labia minora merge with the labia majora. [ 39 ]  In a sexually unstimulated state, the labia minora protects the vaginal and urethral opening by covering them. [ 40 ]  At the base of the labia minora are the  Bartholin's glands , which add a few drops of an alkaline  fluid to the vagina  via ducts; this fluid helps to counteract the acidity of the outer vagina since sperm cannot live in an acidic environment. [ 16 ] [ page needed ]  The  Skene's glands  are possibly responsible for secreting fluid [ 41 ]  during  female ejaculation . [ 41 ] [ 42 ] [ 43 ]


The clitoris is developed from the same embryonic tissue as the penis; it or its  glans  alone consists of as many (or more in some cases) nerve endings as the human penis or glans penis, making it extremely sensitive to touch. [ 44 ] [ 45 ] [ 46 ]  The clitoral glans, which is a small, elongated  erectile  structure, has only one known function—sexual sensations. It is the female's most sensitive  erogenous zone  and the main source of orgasm in women. [ 47 ] [ 48 ] [ 49 ] [ 50 ]  Thick secretions called  smegma  collect around the clitoris. [ 16 ] [ page needed ]


The  vaginal opening  and the  urethral opening  are only visible when the labia minora are parted. These openings have many nerve endings that make them sensitive to touch. They are surrounded by a ring of sphincter muscles called the  bulbocavernosus muscle . Underneath this muscle and on opposite sides of the vaginal opening are the vestibular bulbs, which help the vagina grip the penis by swelling with blood during arousal. Within the vaginal opening is the  hymen , a thin membrane that partially covers the opening in many  virgins . Rupture of the hymen has been historically considered the loss of one's virginity, though, by modern standards, loss of virginity is considered to be the first sexual intercourse. The hymen can be ruptured by activities other than sexual intercourse. The urethral opening connects to the bladder with the urethra; it expels urine from the bladder. This is located below the clitoris and above the vaginal opening. [ 16 ] [ page needed ]


The  breasts  are the subcutaneous tissues on the front thorax of the female body. [ 39 ]  Though they are not technically part of a woman's sexual anatomy, they do have roles in both sexual pleasure and reproduction. [ 51 ]  Breasts are modified sweat glands made up of fibrous tissues and fat that provide support and contain nerves, blood vessels, and lymphatic vessels. [ 39 ]  Their main purpose is to provide milk to a developing infant. Breasts develop during puberty in response to an increase in estrogen. Each adult breast consists of 15 to 20 milk-producing  mammary glands , irregularly shaped lobes that include  alveolar glands  and a lactiferous duct leading to the nipple. The lobes are separated by dense connective tissues that support the glands and attach them to the tissues on the underlying pectoral muscles. [ 39 ]  Other connective tissue, which forms dense strands called suspensory ligaments, extends inward from the skin of the breast to the pectoral tissue to support the weight of the breast. [ 39 ]  Heredity and the quantity of fatty tissue determine the size of the breasts. [ 16 ] [ page needed ]


Men typically find female breasts attractive [ 52 ]  and this holds true for a variety of cultures. [ 53 ] [ 54 ] [ 55 ]  In women,  stimulation of the nipple  seems to result in activation of the brain's genital sensory cortex (the same region of the brain activated by stimulation of the clitoris, vagina, and cervix). [ 56 ]  This may be why many women find nipple stimulation arousing and why some women are able to orgasm by nipple stimulation alone. [ 51 ]


The female internal reproductive organs are the  vagina ,  uterus ,  fallopian tubes , and  ovaries . The vagina is a sheath-like canal that extends from the vulva to the cervix. It receives the penis during intercourse and serves as a depository for sperm. The vagina is also the  birth canal ; it can expand to 10 cm (3.9 in) during labor and delivery. The vagina is located between the  bladder  and the  rectum . The vagina is normally collapsed, but during  sexual arousal  it opens, lengthens, and produces lubrication to allow the insertion of the penis. The vagina has three layered walls; it is a self-cleaning organ with natural bacteria that suppress the production of yeast. [ 16 ] [ page needed ]  The  G-spot , named after the  Ernst Gräfenberg  who first reported it in 1950, may be located in the front wall of the vagina and may cause orgasms. This area may vary in size and location between women; in some it may be absent. Various researchers dispute its structure or existence or regard it as an extension of the clitoris. [ 58 ] [ 59 ] [ 60 ]


The uterus or womb is a hollow, muscular organ where a fertilized egg (ovum) will implant itself and grow into a fetus. [ 16 ] [ page needed ]  The uterus lies in the pelvic cavity between the bladder and the  bowel , and above the vagina. It is usually positioned in a 90-degree angle tilting forward, although in about 20% of women it tilts backwards. [ 39 ]  The uterus has three layers; the innermost layer is the  endometrium , where the egg is implanted. During ovulation, this thickens for implantation. If implantation does not occur, it is sloughed off during menstruation. The cervix is the narrow end of the uterus. The broad part of the uterus is the  fundus . [ 16 ] [ page needed ]


During  ovulation , the ovum travels down the fallopian tubes to the uterus. These extend about four inches (10 cm) from both sides of the uterus. Finger-like projections at the ends of the tubes brush the ovaries and receive the ovum once it is released. The ovum then travels for three to four days to the uterus. [ 16 ] [ page needed ]  After sexual intercourse, sperm swim up this funnel from the uterus. The lining of the tube and its secretions sustain the egg and the sperm, encouraging  fertilization  and nourishing the ovum until it reaches the uterus. If the ovum divides after fertilization,  identical twins  are produced. If separate eggs are fertilized by different sperm, the mother gives birth to non-identical or  fraternal twins . [ 39 ]


The ovaries (female gonads), develop from the same embryonic tissue as the  testicles . The ovaries are suspended by ligaments and are the source where ova are stored and developed before ovulation. The ovaries also produce female hormones  progesterone  and  estrogen . Within the ovaries, each ovum is surrounded by other cells and contained within a capsule called a primary follicle. At puberty, one or more of these follicles are stimulated to mature on a monthly basis. Once matured, these are called  Graafian follicles . [ 16 ] [ page needed ]  The female reproductive system does not produce the ova; about 60,000 ova are present at birth, only 400 of which will mature during the woman's lifetime. [ 39 ]


Ovulation is based on a monthly cycle; the 14th day is the most fertile. On days one to four, menstruation and production of estrogen and progesterone decreases, and the endometrium starts thinning. The endometrium is sloughed off for the next three to six days. Once menstruation ends, the cycle begins again with an FSH surge from the pituitary gland. Days five to thirteen are known as the pre-ovulatory stage. During this stage, the pituitary gland secretes follicle-stimulating hormone (FSH). A negative feedback loop is enacted when estrogen is secreted to inhibit the release of FSH. Estrogen thickens the endometrium of the uterus. A surge of  luteinizing hormone  (LH) triggers ovulation.


On day 14, the LH surge causes a Graafian follicle to surface the ovary. The follicle ruptures and the ripe ovum is expelled into the abdominal cavity. The fallopian tubes pick up the ovum with the  fimbria . The cervical mucus changes to aid the movement of sperm. On days 15 to 28—the post-ovulatory stage, the Graafian follicle—now called the  corpus luteum —secretes estrogen. Production of progesterone increases, inhibiting LH release. The endometrium thickens to prepare for implantation, and the ovum travels down the fallopian tubes to the uterus. If the ovum is not fertilized and does not implant, menstruation begins. [ 16 ] [ page needed ]


The sexual response cycle is a model that describes the physiological responses that occur during sexual activity. This model was created by  William Masters  and  Virginia Johnson . According to Masters and Johnson, the human sexual response cycle consists of four phases; excitement, plateau, orgasm, and resolution, also called the EPOR model. During the excitement phase of the EPOR model, one attains the intrinsic motivation to have sex. The plateau phase is the precursor to orgasm, which may be mostly biological for men and mostly psychological for women. Orgasm is the release of tension, and the resolution period is the unaroused state before the cycle begins again. [ 16 ] [ page needed ]


The male sexual response cycle starts in the excitement phase; two centers in the spine are responsible for erections. Vasoconstriction in the penis begins, the heart rate increases, the scrotum thickens, the spermatic cord shortens, and the testicles become engorged with blood. In the plateau phase, the penis increases in diameter, the testicles become more engorged, and the Cowper's glands secrete pre-seminal fluid. The orgasm phase, during which rhythmic contractions occur every 0.8 seconds, [ 61 ] [ verification needed ]  consists of two phases; the emission phase, in which contractions of the vas deferens, prostate, and seminal vesicles encourage ejaculation, which is the second phase of orgasm. Ejaculation is called the expulsion phase; it cannot be reached without an orgasm. In the resolution phase, the male is now in an unaroused state consisting of a  refractory (rest) period  before the cycle can begin. This rest period may increase with age. [ 16 ] [ page needed ]


The female sexual response begins with the excitement phase, which can last from several minutes to several hours. Characteristics of this phase include increased heart and respiratory rate, and an elevation of blood pressure. Flushed skin or blotches of redness may occur on the chest and back; breasts increase slightly in size and nipples may become hardened and erect. The onset of  vasocongestion  results in swelling of the clitoris, labia minora, and vagina. The muscle that surrounds the vaginal opening tightens and the uterus elevates and grows in size. The vaginal walls begin to produce a lubricating liquid. The second phase, called the plateau phase, is characterized primarily by the intensification of the changes begun during the excitement phase. The plateau phase extends to the brink of orgasm, which initiates the resolution stage; the reversal of the changes begun during the excitement phase. During the orgasm stage the heart rate, blood pressure, muscle tension, and breathing rates peak. The pelvic muscle near the vagina, the anal sphincter, and the uterus contract. Muscle contractions in the vaginal area create a high level of pleasure, though all orgasms are centered in the clitoris. [ 16 ] [ page needed ] [ 62 ] [ 63 ] [ 64 ]


Sexual disorders, according to the DSM-IV-TR, are disturbances in sexual desire and psycho-physiological changes that characterize the sexual response cycle and cause marked distress and interpersonal difficulty. Sexual dysfunctions are a result of physical or psychological disorders. Physical causes include hormonal imbalance, diabetes, heart disease and more; psychological causes include but are not limited to stress, anxiety, and depression. [ 65 ]  Sexual dysfunction affects both men and women. There are four major categories of sexual problems in women: desire disorders, arousal disorders, orgasmic disorders, and sexual pain disorders. [ 16 ] [ page needed ]  Sexual desire disorder occurs when an individual lacks sexual desire because of hormonal changes, depression, and pregnancy. Arousal disorder is a female sexual dysfunction leading to a lack of vaginal lubrication. In addition, blood flow problems may affect arousal disorder. Lack of orgasm, also known as anorgasmia, is another sexual dysfunction in women. The last sexual disorder is painful intercourse, which can be caused by factors including pelvic mass, scar tissue, and sexually transmitted infections. [ 66 ]


Three common sexual disorders for men are sexual desire disorder, ejaculation disorder, and erectile dysfunction. Lack of sexual desire in men may be caused by physical issues like low testosterone or psychological factors such as anxiety and depression. [ 67 ]  Ejaculation disorders include retrograde ejaculation, retarded ejaculation, and premature ejaculation. Erectile dysfunction is an inability to initiate and maintain an erection during intercourse. [ 68 ]


As one form of behavior, the psychological aspects of sexual expression have been studied in the context of emotional involvement, gender identity, intersubjective intimacy, and Darwinian reproductive efficacy. Sexuality in humans generates profound emotional and psychological responses. Some theorists identify sexuality as the central source of human personality. [ 69 ]  Psychological studies of sexuality focus on psychological influences that affect sexual behavior and experiences. [ 15 ] [ page needed ]  Early psychological analyses were carried out by  Sigmund Freud , who believed in a  psychoanalytic  approach. He also proposed the concepts of  psychosexual development  and the  Oedipus complex , among other theories. [ 70 ]


Gender identity is a person's sense of their own  gender , whether male, female, or  non-binary . [ 71 ]  Gender identity can correlate with  assigned sex  at birth or can differ from it. [ 72 ]  All societies have a set of gender categories that can serve as the basis of the formation of a person's  social identity  in relation to other members of society. [ 73 ]


Sexual behavior and intimate relationships are strongly influenced by a person's sexual orientation. [ 74 ]


Sexual orientation is an enduring pattern of  romantic  or  sexual attraction  (or a combination of these) to persons of the opposite sex, same sex, or both sexes. [ 74 ]  Heterosexual people are romantically/sexually attracted to the members of the opposite sex, gay and lesbian people are romantically/sexually attracted to people of the same sex, and those who are bisexual are romantically/sexually attracted to both sexes. [ 5 ]


The idea that homosexuality results from reversed gender roles is reinforced by the media's portrayal of gay men as feminine and lesbians as masculine. [ 75 ] [ page needed ]  However, a person's conformity or non-conformity to gender stereotypes does not always predict sexual orientation. Society believes that if a man is masculine, he is heterosexual, and if a man is feminine, he is homosexual. There is no strong evidence that a homosexual or bisexual orientation must be associated with atypical gender roles. By the early 21st century, homosexuality was no longer considered to be a pathology. Theories have linked many factors, including genetic, anatomical, birth order, and hormones in the prenatal environment, to homosexuality. [ 75 ] [ page needed ]


Other than the need to procreate, there are many other reasons people have sex. According to one study conducted on college students (Meston & Buss, 2007), the four main reasons for sexual activities are physical attraction, as a means to an end, to increase emotional connection, and to alleviate insecurity. [ 76 ]


Until Sigmund Freud published his  Three Essays on the Theory of Sexuality  in 1905, children were often regarded as  asexual , having no sexuality until later development. Sigmund Freud was one of the first researchers to take child sexuality seriously. His ideas, such as psychosexual development and the  Oedipus conflict , have been much debated but acknowledging the existence of child sexuality was an important development. [ 77 ] [ page needed ]


Freud gave sexual drives an importance and centrality in human life, actions, and behavior; he said sexual drives exist and can be discerned in children from birth. He explains this in his theory of  infantile sexuality , and says sexual energy ( libido ) is the most important motivating force in adult life. Freud wrote about the importance of interpersonal relationships to one's sexual and emotional development. From birth, the mother's connection to the infant affects the infant's later capacity for pleasure and  attachment . [ 78 ]  Freud described two currents of emotional life; an affectionate current, including our bonds with the important people in our lives; and a sensual current, including our wish to gratify sexual impulses. During adolescence, a young person tries to integrate these two emotional currents. [ 79 ]


Alfred Kinsey  also examined child sexuality in his  Kinsey Reports . Children are naturally curious about their bodies and sexual functions. For example, they wonder where babies come from, they notice the differences between males and females, and many engage in  genital play , which is often mistaken for masturbation. Child sex play, also known as  playing doctor , includes exhibiting or inspecting the genitals. Many children take part in some sex play, typically with siblings or friends. [ 77 ] [ page needed ]  Sex play with others usually decreases as children grow, but they may later possess romantic interest in their peers. Curiosity levels remain high during these years, but the main surge in sexual interest occurs in adolescence. [ 77 ] [ page needed ]


Adult sexuality originates in childhood. However, like many other human capacities, sexuality is not fixed, but matures and develops. A common stereotype associated with old people is that they tend to lose interest and the ability to engage in sexual acts once they reach late adulthood. This misconception is reinforced by Western popular culture, which often ridicules older adults who try to engage in sexual activities. Age does not necessarily change the need or desire to be sexually expressive or active. A couple in a long-term relationship may find that the frequency of their sexual activity decreases over time and the type of sexual expression may change, but feelings of intimacy may continue to grow and develop over time. [ 80 ]


Human sexuality can be understood as part of the social life of humans, which is governed by implied rules of behavior and the status quo. This narrows the view to groups within a society. [ 15 ] [ page needed ]  The socio-cultural context of society, including the effects of politics and the mass media, influences and forms social norms. Throughout history, social norms have been changing and continue to change as a result of movements such as the sexual revolution and the rise of  feminism . [ 83 ] [ 84 ]


The age and manner in which children are informed of issues of sexuality is a matter of sex education. The school systems in almost all developed countries have some form of sex education, but the nature of the issues covered varies widely. In some countries, such as Australia and much of Europe, age-appropriate sex education often begins in pre-school, whereas other countries leave sex education to the pre-teenage and teenage years. [ 85 ]  Sex education covers a range of topics, including the physical, mental, and social aspects of sexual behavior. Communities have differing opinions on the appropriate age for children to learn about sexuality. According to  Time  magazine and  CNN , 74% of teenagers in the United States reported that their major sources of sexual information were their peers and the media, compared to 10% who named their parents or a sex education course. [ 16 ]


In the United States, some sex education programs encourage  abstinence-only , the choice to restrain oneself from sexual activity. In contrast,  comprehensive sex education  aims to encourage students to take charge of their own sexuality and know how to have safe, healthy, and pleasurable sex if and when they choose to do so. [ 86 ]


Proponents for an abstinence-only education believe that teaching a comprehensive curriculum would encourage teenagers to have sex, while proponents for comprehensive sex education argue that many teenagers will have sex regardless and should be equipped with knowledge of how to have sex responsibly. According to data from the National Longitudinal Survey of Youth, many teens who intend to be abstinent fail to do so, and when these teenagers do have sex, many do not use safe sex practices such as contraceptives. [ 87 ]


Sexuality has been an important, vital part of human existence throughout history. [ 88 ] [ page needed ]  All civilizations have managed sexuality through sexual standards, representations, and behavior. [ 88 ] [ page needed ]


Before the rise of agriculture, groups of hunter-gatherers and nomadic groups inhabited the world. These groups had less restrictive sexual standards that emphasized sexual pleasure and enjoyment, but with definite rules and constraints. Some underlying continuities or key regulatory standards contended with the tension between recognition of pleasure, interest, and the need to procreate for the sake of social order and economic survival. Hunter-gatherers also placed high value on certain types of sexual symbolism.


A common tension in hunter-gatherer societies is expressed in their art, which emphasized male sexuality and prowess, but also blurred gender lines in sexual matters. One example of these male-dominated portrayals is the  Egyptian creation myth , in which the sun god  Atum  masturbates in the water, creating the  Nile River . In  Sumerian  myth, the gods' semen filled the  Tigris . [ 88 ] [ page needed ]


Once agricultural societies emerged, the sexual framework shifted in ways that persisted for many millennia in much of Asia, Africa, Europe, and parts of the Americas. One common characteristic new to these societies was the collective supervision of sexual behavior due to urbanization and the growth of population and population density. Children would commonly witness parents having sex because many families shared the same sleeping quarters. Due to land ownership, determination of children's paternity became important, and society and family life became patriarchal. [ 89 ]  These changes in sexual ideology were used to control female sexuality and to differentiate standards by gender. With these ideologies, sexual possessiveness and increases in jealousy emerged.


While retaining the precedents of earlier civilizations, each classical civilization established a somewhat distinctive approach to gender, artistic expression of sexual beauty, and to behaviors such as homosexuality. Some of these distinctions are portrayed in sex manuals, which were also common among civilizations in China, Greece, Rome, Persia, and India; each has its own sexual history. [ 88 ] [ page needed ]


Before the  High Middle Ages , homosexual acts appear to have been ignored or tolerated by the Christian church. [ 90 ]  During the 12th century, hostility toward homosexuality began to spread throughout religious and secular institutions. By the end of the 19th century, it was viewed as a pathology. [ 90 ]


During the beginning of the  Industrial Revolution  of the 18th and 19th centuries, many changes in sexual standards occurred. New artificial birth control devices such as the  condom  and  diaphragm  were introduced. Doctors started claiming a new role in sexual matters, urging that their advice was crucial to sexual morality and health. New pornographic industries grew, and Japan adopted its first laws against homosexuality. In Western societies, the definition of homosexuality was constantly changing; Western influence on other cultures became more prevalent. New contacts created serious issues around sexuality and sexual traditions. There were also major shifts in sexual behavior. During this period, puberty began occurring at younger ages, so a new focus on adolescence as a time of sexual confusion and danger emerged. There was a new focus on the purpose of marriage; it was increasing regarded as being for love rather than only for economics and reproduction. [ 88 ] [ page needed ]


Havelock Ellis  and Sigmund Freud adopted more accepting stances toward homosexuality; Ellis said homosexuality was inborn and therefore not immoral, not a disease, and that many homosexuals made significant contributions to society. [ 90 ]  Freud wrote that all human beings as capable of becoming either heterosexual or homosexual; neither orientation was assumed to be innate. [ 75 ] [ page needed ]  According to Freud, a person's orientation depended on the resolution of the Oedipus complex. [ 91 ]  He said male homosexuality resulted when a young boy had an authoritarian, rejecting mother and turned to his father for love and affection, and later to men in general. He said female homosexuality developed when a girl loved her mother and identified with her father and became fixated at that stage. [ 75 ] [ page needed ]


Alfred Kinsey initiated the modern era of sex research. He collected data from questionnaires given to his students at  Indiana University , but then switched to personal interviews about sexual behaviors. Kinsey and his colleagues sampled 5,300 men and 5,940 women. He found that most people masturbated, that many engaged in oral sex, that women are capable of having multiple orgasms, and that many men had had some type of homosexual experience in their lifetimes. [ 16 ] [ page needed ]


Before William Masters, a physician, and Virginia Johnson, a  behavioral scientist , the study of anatomy and physiological studies of sex was still limited to experiments with laboratory animals. Masters and Johnson started to directly observe and record the physical responses in humans that are engaged in sexual activity under laboratory settings. They observed 10,000 episodes of sexual acts between 312 men and 382 women. This led to methods of treating clinical problems and abnormalities. Masters and Johnson opened the first sex therapy clinic in 1965. In 1970, they described their therapeutic techniques in their book,  Human Sexual Inadequacy . [ 16 ] [ page needed ]


The first edition of the  Diagnostic and Statistical Manual of Mental Disorders , published by the  American Psychiatric Association , classified homosexuality as a mental illness, and more specifically, a "sociopathic personality disturbance". [ 92 ]  This definition remained the professional understanding of homosexuality until 1973 when the American Psychiatric Association removed homosexuality from their list of diagnoses for mental disorders. [ 92 ]  Through her research of heterosexual and homosexual men,  Evelyn Hooker  revealed that there was no correlation between homosexuality and psychological maladjustment, [ 93 ]  and her findings played a pivotal role in shifting the scientific community away from the perspective that homosexuality was something that needed to be treated or cured. [ 94 ]


European conquerors/colonists discovered that many non-European cultures had expressions of sexuality and gender which differed from European notion of  heterosexual   cisnormativity . These would include  transgender  practices. [ 95 ]  In  1516 ,  Vasco Núñez de Balboa , a Spanish explorer, discovered indigenous people in Central America, among whom several indigenous men who dressed like women and had sex with each other, resulting in him feeding forty of these men to his dogs for having non- gender conforming  behaviors and sexuality. [ 95 ] [ 96 ]  In North America and the United States, Europeans have used claims of sexual immorality to justify discrimination against racial and ethnic minorities. [ 97 ]


Scholars also study the ways in which  colonialism  has affected sexuality today and argue that due to  racism  and  slavery  it has been dramatically changed from the way it had previously been understood. [ 98 ] [ 99 ]


In her book,  Carnal Knowledge and Imperial Power: Gender, Race, and Morality in Colonial Asia , Laura Stoler investigates how the  Dutch  colonists used sexual control and gender-specific sexual sanctions to distinguish between the rulers from the ruled and enforce colonial domination onto the people of  Indonesia . [ 100 ]


In America, there are 155 native tribes that are recorded to have embraced  two-spirit  people within their tribes, but the total number of tribes could be greater than what is documented. [ 101 ]  Two-spirit people were and still are members of communities who do not fall under Western gender categories of male and female, but rather under a " third gender " category. [ 102 ]  This system of gender contradicts both the gender binary and the assertion that sex and gender are the same. [ 103 ]  Instead of conforming to traditional roles of men and women, two-spirit fill a special niche in their communities.


For example, two-spirited people are commonly revered for possessing special wisdom and spiritual powers. [ 103 ]  Two-spirited people also can take part in marriages, either monogamous and polygamous ones. [ 104 ]  Historically, European colonizers perceived relationships involving two-spirited people as homosexuality, and therefore believed in the moral inferiority of native people. [ 103 ]  In reaction, colonizers began to impose their own religious and social norms on indigenous communities, diminishing the role of two-spirit people in native cultures. [ 105 ]  Within reservations, the Religious Crime Code of the 1880s explicitly aimed to "aggressively attack Native sexual and marriage practices". [ 103 ]  The goal of colonizers was for native peoples to assimilate into Euro-American ideals of family, sexuality, gender expression, and more. [ 103 ]


The link between constructed sexual meanings and racial ideologies has been studied. According to Joane Nagel, sexual meanings are constructed to maintain racial-ethnic-national boundaries by the denigration of "others" and regulation of sexual behavior within the group. She writes, "both adherence to and deviation from such approved behaviors, define and reinforce racial, ethnic, and nationalist regimes". [ 106 ] [ 107 ]  In the United States people of color face the effects of colonialism in different ways with stereotypes such as the Mammy and Jezebel for Black women;  lotus blossom and dragon lady  for Asian women; and the spicy Latina. [ 108 ]  These stereotypes contrast with standards of sexual conservatism, creating a dichotomy that dehumanizes and demonizes the stereotyped groups. An example of a stereotype that lies at the intersection of racism, classism, and  misogyny  is the archetype of the  welfare queen . Cathy Cohen describes how the welfare queen stereotype demonizes poor black single mothers for deviating from conventions surrounding family structure. [ 109 ]


Reproductive and sexual rights  encompass the concept of applying  human rights  to issues related to reproduction and sexuality. [ 110 ]  This concept is a modern one, and remains controversial since it deals, directly and indirectly, with issues such as  contraception ,  LGBT rights ,  abortion ,  sex education , freedom to choose a partner, freedom to decide whether to be sexually active or not, right to bodily integrity, freedom to decide whether or not, and when, to have children. [ 111 ] [ 112 ]  These are all global issues that exist in all cultures to some extent, but manifest differently depending on the specific contexts.


According to the Swedish government, "sexual rights include the right of all people to decide over their own bodies and sexuality" and "reproductive rights comprise the right of individuals to decide on the number of children they have and the intervals at which they are born." [ 113 ]  Such rights are not accepted in all cultures, with practices such criminalization of consensual sexual activities (such as those related to homosexual acts and sexual acts outside marriage), acceptance of  forced marriage  and  child marriage , failure to criminalize all non-consensual sexual encounters (such as  marital rape ),  female genital mutilation , or restricted availability of contraception, being common around the world. [ 114 ] [ 115 ]


In 1915,  Emma Goldman  and  Margaret Sanger , [ 116 ]  leaders of the birth control movement, began to spread information regarding contraception in opposition to the laws, such as the Comstock Law, [ 117 ]  that demonized it. One of their main purposes was to assert that the birth control movement was about empowering women with personal reproductive and economic freedom for those who could not afford to parent a child or simply did not want one. Goldman and Sanger saw it necessary to educate people as contraceptives were quickly being stigmatized as a population control tactic due to being a policy limiting births, disregarding that this limitation did not target ecological, political, or large economic conditions. [ 118 ]  This stigma targeted lower-class women who had the most need of access to contraception.


Birth control finally began to lose stigma in 1936 when the ruling of  U.S. v. One Package [ 119 ]  declared that prescribing contraception to save a person's life or well-being was no longer illegal under the Comstock Law. Although opinions varied on when birth control should be available to women, by 1938, there were 347 birth control clinics in the United States but advertising their services remained illegal.


The stigma continued to lose credibility as First Lady Eleanor Roosevelt publicly showed her support for birth control through the four terms her husband served (1933–1945). However, it was not until 1966 that the Federal Government began to fund family planning and subsidized birth control services for lower-class women and families at the order of President Lyndon B. Johnson. This funding continued after 1970 under the Family Planning Services and Population Research Act. [ 120 ]  Today, all Health Insurance Marketplace plans are required to cover all forms of contraception, including sterilization procedures, as a result of The Affordable Care Act signed by President Barack Obama in 2010. [ 121 ]


In 1981, doctors diagnosed the first reported cases of  AIDS  in America. The disease disproportionately affected and continues to affect gay and bisexual men, especially black and Latino men. [ 122 ]  The Reagan administration is criticized for its apathy towards the AIDS epidemic, and audio recordings reveal that Ronald Reagan's press secretary Larry Speakes viewed the epidemic as a joke, mocking AIDS by calling it the "gay plague". [ 123 ]  The epidemic also carried stigma coming from religious influences. For example, Cardinal Krol voiced that AIDS was "an act of vengeance against the sin of homosexuality", which clarifies the specific meaning behind the pope's mention of "the moral source of AIDS." [ 124 ]


Activism  during the AIDS crisis focused on promoting safe sex practices to raise awareness that the disease could be prevented. The "Safe Sex is Hot Sex" campaign, for example, aimed to promote the use of condoms. [ 125 ]  Campaigns by the U.S. government, however, diverged from advocacy of safe sex. In 1987, Congress even denied federal funding from awareness campaigns that "[promoted] or [encouraged], directly or indirectly, homosexual activities". [ 125 ]  Instead, campaigns by the government primarily relied on scare tactics in order to instill fear in men who had sex with other men. [ 125 ]


In addition to prevention campaigns, activists also sought to counteract narratives that led to the "social death" for people living with AIDS. [ 126 ]   Gay men  from San Francisco and New York City created the Denver Principles, a foundational document that demanded the rights, agency, and dignity of people living with AIDS. [ 126 ]


In his article "Emergence of Gay Identity and Gay Social Movements in Developing Countries", Matthew Roberts discusses how international AIDS prevention campaigns created opportunities for gay men to interact with other openly gay men from other countries. [ 127 ]  These interactions allowed western gay "culture" to be introduced to gay men in countries where homosexuality was not an important identifier. Thus, group organizers self-identified as gay more and more, creating the basis for further development of gay consciousness in different countries. [ 127 ]


In humans, sexual intercourse has been shown to have health benefits, [ 128 ]  such as an improved sense of smell, [ 129 ]  reduction in  stress  and blood pressure, [ 130 ] [ 131 ]  increased  immunity , [ 132 ]  and decreased risk of  prostate cancer . [ 133 ] [ 134 ] [ 135 ]  Sexual intimacy and orgasms increase levels of oxytocin, which helps people bond and build trust. [ 136 ] [ 137 ] [ 138 ]  Some of these benefits, such as stress reduction, also apply to  masturbation , as distinct from sexual intercourse with another person. Masturbation is also a healthy element of sexual development in itself. [ 139 ] [ 140 ]


A long-term study of 3,500 people between ages 30 and 101 by clinical neuropsychologist David Weeks, MD, head of old-age psychology at the  Royal Edinburgh Hospital  in Scotland, said he found that "sex helps you look between four and seven years younger", according to impartial ratings of the subjects' photographs. Exclusive causation, however, is unclear, and the benefits may be indirectly related to sex and directly related to significant reductions in stress, greater contentment, and better sleep that sex promotes. [ 141 ] [ 142 ] [ 143 ]


Sexual intercourse can also be a  disease vector . [ 144 ]  There are 19 million new cases of sexually transmitted infections (STI) every year in the U.S., [ 145 ]  and worldwide there are over 340 million sexually transmitted infections each year. [ 146 ]  More than half of these occur in adolescents and young adults aged 15–24 years. [ 147 ]  At least one in four US teenage girls has a sexually transmitted infection. [ 145 ] [ 148 ]  In the U.S., about 30% of 15- to 17-year-olds have had sexual intercourse, but only about 80% of 15- to 19-year-olds report using condoms for their first sexual intercourse. [ 149 ]  In one study, more than 75% of young women age 18–25 years felt they were at low risk of acquiring an STI. [ 150 ]


People both consciously and subconsciously seek to attract others with whom they can form deep relationships. This may be for companionship, procreation, or an intimate relationship. This involves interactive processes whereby people find and attract potential partners and maintain a relationship. These processes, which involve attracting one or more partners and maintaining sexual interest, can include:


Sexual attraction is attraction on the basis of  sexual desire  or the quality of arousing such interest. [ 157 ] [ 158 ]  Sexual attractiveness or sex appeal is an individual's ability to attract the sexual or erotic interest of another person and is a factor in  sexual selection  or  mate choice . The attraction can be to the  physical  or other qualities or traits of a person, or to such qualities in the context in which they appear. The attraction may be to a person's  aesthetics  or movements or to their voice or smell, besides other factors. The attraction may be enhanced by a person's adornments, clothing, perfume,  hair length  and  style , and anything else which can attract the sexual interest of another person. It can also be influenced by  individual   genetic ,  psychological , or cultural factors, or to other, more amorphous qualities of the person. Sexual attraction is also a response to another person that depends on a combination of the person possessing the traits and also on the criteria of the person who is attracted.


Though attempts have been made to devise objective criteria of sexual attractiveness and measure it as  one of several bodily forms of   capital asset  ( see  erotic capital ), a person's sexual attractiveness is to a large extent a subjective measure dependent on another person's interest, perception, and sexual orientation. For example, a gay or lesbian person would typically find a person of the  same sex  to be more attractive than one of the other sex. A  bisexual person  would find either sex to be attractive. [ 159 ]


In addition, there are  asexual  people, who usually do not experience sexual attraction for either sex, though they may have romantic attraction (homoromantic, biromantic or heteroromantic).  Interpersonal attraction  includes factors such as  physical or psychological similarity ,  familiarity  or possessing a preponderance of  common or familiar features ,  similarity ,  complementarity ,  reciprocal liking , and  reinforcement . [ 160 ]


The ability of a person's physical and other qualities to create a sexual interest in others is the basis of their use in  advertising ,  music video ,  pornography ,  film , and other visual media, as well as in  modeling ,  sex work  and other occupations.


Globally, laws regulate human sexuality in several ways, including criminalizing particular sexual behaviors, granting individuals the privacy or  autonomy  to make their own sexual decisions, protecting individuals with regard to equality and non-discrimination, recognizing and protecting other individual rights, as well as legislating matters regarding marriage and the family, and creating laws protecting individuals from violence, harassment, and persecution. [ 161 ]


In the United States, there are two fundamentally different approaches, applied in different states, regarding the way the law is used to attempt to govern a person's sexuality. The "black letter" approach to law focuses on the study of pre-existing legal precedent and attempts to offer a clear framework of rules within which lawyers and others can work. [ 161 ]  In contrast, the socio-legal approach focuses more broadly on the relationship between the law and society, and offers a more contextualized view of the relationship between legal and social change. [ 161 ]


Issues regarding human sexuality and human sexual orientation came to the forefront in Western law in the latter half of the twentieth century, as part of the  gay liberation  movement's encouragement of LGBT individuals to " come out of the closet " and engage with the legal system, primarily through courts. Therefore, many issues regarding human sexuality and the law are found in the opinions of the courts. [ 162 ]


While the issue of privacy has been useful to sexual rights claims, some scholars have criticized its usefulness, saying that this perspective is too narrow and restrictive. The law is often slow to intervene in certain forms of coercive behavior that can limit individuals' control over their own sexuality (such as female genital mutilation,  forced marriages  or lack of access to reproductive health care). Many of these injustices are often perpetuated wholly or in part by private individuals rather than state agents, and as a result, there is an ongoing debate about the extent of state responsibility to prevent harmful practices and to investigate such practices when they do occur. [ 161 ]


State intervention with regards to sexuality also occurs, and is considered acceptable by some, in certain instances (e.g. same-sex sexual activity or  prostitution ). [ 161 ]


The legal systems surrounding prostitution are a topic of debate. Proponents for criminalization argue that sex work is an immoral practice that should not be tolerated, while proponents for decriminalization point out how criminalization does more harm than good. Within the feminist movement, there is also a debate over whether sex work is inherently objectifying and exploitative or whether sex workers have the agency to sell sex as a service. [ 163 ]


When sex work is criminalized, sex workers do not have support from law enforcement when they fall victim to violence. In a 2003 survey of street-based sex workers in NYC, 80% said they had been threatened with or experienced violence, and many said the police were no help. 27% said they had experienced violence from police officers themselves. [ 164 ]  Different identities such as being black, transgender, or poor can result in a person being more likely to be criminally profiled by the police. For example, in New York, there is a law against "loitering for the purpose of engaging in prostitution", which has been nicknamed the "walking while trans" law because of how often transgender women are assumed to be sex workers and arrested for simply walking out in public. [ 165 ]


In some  religions , sexual behavior is regarded as primarily spiritual. In others it is treated as primarily physical. Some hold that sexual behavior is only spiritual within certain kinds of relationships, when used for specific purposes, or when incorporated into religious ritual. In some religions there are no distinctions between the physical and the spiritual, whereas some religions view human sexuality as a way of completing the gap that exists between the spiritual and the physical. [ 166 ]


Many religious conservatives, especially those of  Abrahamic religions  and  Christianity  in particular, tend to view sexuality in terms of behavior (i.e. homosexuality or heterosexuality is what someone does). These conservatives tend to promote  celibacy  for gay people, and may also tend to believe that sexuality can be changed through  conversion therapy [ 167 ]  or  prayer  to become an  ex-gay . They may also see homosexuality as a form of mental illness, something that ought to be criminalized, an immoral abomination, caused by ineffective parenting, and view  same-sex marriage  as a threat to society. [ 168 ]


On the other hand, most religious liberals define sexuality-related labels in terms of sexual attraction and self-identification. [ 167 ]  They may also view same-sex activity as morally neutral and as legally acceptable as opposite-sex activity, unrelated to mental illness, genetically or environmentally caused (but not as the result of bad parenting), and fixed. They also tend to be more in favor of same-sex marriage. [ 168 ]


According to  Judaism , sex between a man and woman within marriage is sacred and should be regularly enjoyed; celibacy is considered sinful. [ 16 ] [ page needed ] [ 169 ] [ note 1 ]


Desire, including sexual desire and lust, were considered immoral and sinful, according to some authors. [ 170 ] [ 171 ] [ 172 ]   Elaine Pagels  says, "By the beginning of the fifth century,  Augustine  had actually declared that spontaneous sexual desire is the proof of—and penalty for—universal original sin", though that this view goes against "most of his Christian predecessors". [ 171 ]  According to  Jennifer Wright Knust ,  Paul  framed desire a force Christians gained control over whereas non-Christians were "enslaved" by it; [ 170 ]  and he also said the bodies of Christians were members of  Christ's body  and thus sexual desire must be eschewed. [ 170 ]


The  Roman Catholic Church  teaches that sexuality is "noble and worthy" [ 173 ]  and has a unitive and procreative end. [ 174 ] [ 175 ]  For this reason, sexual activity's ideal should occur in the context of a marriage between a man and a woman, and open to the possibility of life.  Pope Francis  teaches in  Amoris laetitia  against "an attitude that would solve everything by applying general rules or deriving undue conclusions from particular theological considerations. [ 176 ]  and that he also warns that "not all discussions of doctrinal, moral or pastoral issues need to be settled by interventions of the magisterium." [ 177 ]  and that "We have been called to form consciences, not to replace them." [ 178 ]  The church has authoritative teachings on sexuality found in the catechism. [ 179 ]  The church places primacy of conscience especially on the regulation of births. [ 180 ]


The  Anglican Church  teaches that human sexuality is a gift from a loving God designed to be between a man and a woman in a monogamous lifetime union of marriage. It also views singleness and dedicated celibacy as Christ-like. It states that people with same sex attraction are loved by God and are welcomed as full members of the  Body of Christ , while the Church leadership has a variety of views in regard to homosexual expression and ordination. Some expressions of sexuality are considered sinful including "promiscuity, prostitution, incest, pornography, pedophilia, predatory sexual behavior, and sadomasochism (all of which may be heterosexual and homosexual), adultery, violence against wives, and female circumcision". The Church is concerned with pressures on young people to engage sexually and encourages abstinence. [ 181 ]


In matters of sexuality, several  Evangelical  churches promote the  virginity pledge  among young Evangelical Christians, who are invited to commit themselves during a public ceremony to  sexual abstinence  until  Christian marriage . [ 182 ]  This pledge is often symbolized by a  purity ring . [ 183 ]


In evangelical churches, young adults and unmarried couples are encouraged to marry early in order to live a sexuality according to the will of God. [ 184 ]


Although some churches are discreet on the subject, other evangelical churches in United States and Switzerland speak of a satisfying sexuality as a gift from God and a component of a harmonious Christian marriage, in messages during  worship services  or conferences. [ 185 ] [ 186 ]  Many evangelical books and websites are specialized on the subject. [ 187 ]


The  perceptions of homosexuality in the Evangelical Churches  are varied. They range from  liberal  through  moderate  to  conservative . [ 188 ] [ 189 ]


The  christian marriage  is presented by some churches as a protection against sexual misconduct and a compulsory step to obtain a position of responsibility in the church.  [ 190 ]  This concept, however, has been challenged by numerous sex scandals involving married evangelical leaders.  [ 191 ] [ 192 ]  Finally, evangelical theologians recalled that  celibacy  should be more valued in the Church today, since the gift of  celibacy  was taught and lived by  Jesus Christ  and  Paul of Tarsus .  [ 193 ] [ 194 ]


In  Islam , desire for sex is considered to be a natural urge that should not be suppressed, although the concept of free sex is not accepted; these urges should be fulfilled responsibly. Marriage is considered to be a good deed; it does not hinder spiritual wayfaring. The term used for marriage within the  Quran  is  nikah . [ 195 ]  Although Islamic sexuality is restrained via  Islamic sexual jurisprudence , it emphasizes sexual pleasure within marriage. It is acceptable for a  man to have more than one wife , but he must take care of those wives physically, mentally, emotionally, financially, and spiritually. [ 196 ]  Muslims believe that sexual intercourse is an act of worship that fulfils emotional and physical needs, and that producing children is one way in which humans can contribute to God's creation, and Islam discourages celibacy once an individual is married.


However, homosexuality is strictly forbidden in Islam, and some  Muslim scholars  have suggested that gay people should be put to death. [ 197 ]


Some have argued that Islam has an open and playful approach to sex [ 198 ]  so long as it is within marriage, free of lewdness, fornication and adultery.


Hinduism  emphasizes that sex is only appropriate between husband and wife, in which satisfying sexual urges through sexual pleasure is an important duty of marriage. Any sex before marriage is considered to interfere with intellectual development, especially between birth and the age of 25, which is said to be brahmacharya and this should be avoided.  Kama  (sensual pleasures) is one of the four purusharthas or aims of life (dharma, artha, kama, and moksha). [ 199 ]  The Hindu  Kama Sutra  deals partially with sexual intercourse; it is not exclusively a sexual or religious work. [ 200 ] [ 201 ]


Sikhism  views  chastity  as important, as Sikhs believe that the divine spark of  Waheguru  is present inside every individual's body, therefore it is important for one to keep clean and pure. Sexual activity is limited to married couples, and extramarital sex is forbidden. Marriage is seen as a commitment to  Waheguru  and should be viewed as part of spiritual companionship, rather than just sexual intercourse, and  monogamy  is deeply emphasized in Sikhism. Any other way of living is discouraged, including celibacy and homosexuality. However, in comparison to other religions, the issue of sexuality in Sikhism is not considered one of paramount importance. [ 202 ]


Human female sexuality  encompasses a broad range of behaviors and processes, including female  sexual identity  and  sexual behavior , the  physiological ,  psychological ,  social ,  cultural ,  political , and  spiritual  or  religious  aspects of sexual activity. Various aspects and dimensions of female sexuality, as a part of  human sexuality , have also been addressed by principles of  ethics ,  morality , and  theology . In almost any historical era and culture, the arts, including literary and visual arts, as well as popular culture, present a substantial portion of a given society's views on human sexuality, which includes both implicit (covert) and explicit (overt) aspects and manifestations of feminine sexuality and behavior.


In most societies and  legal jurisdictions , there are  legal bounds on what sexual behavior is permitted . Sexuality varies across the cultures and regions of the world, and has continually changed throughout history, and this also applies to female sexuality. Aspects of female sexuality include issues pertaining to  body image ,  self-esteem ,  personality ,  sexual orientation ,  values  and  attitudes ,  gender roles ,  relationships , activity options, and communication.


While most women are  heterosexual , significant minorities are  homosexual  or varying degrees of  bisexual . Bisexual females are more common than bisexual males. [ 1 ]


Sexual activity can encompass various  sexually stimulating  factors ( physiological stimulation  or  psychological stimulation ), including  sexual fantasies  and different  sex positions , or the use of  sex toys . [ 2 ] [ 3 ] [ 4 ]   Foreplay  may precede some sexual activities, often leading to  sexual arousal  of the partners. [ 5 ]  It is also common for people to be sexually satisfied by being kissed, touched  erotically , or held. [ 6 ]


Orgasm , or sexual climax, is the sudden discharge of accumulated sexual tension during the  sexual response cycle , resulting in rhythmic  muscular contractions  in the  pelvic  region characterized by an intense sensation of pleasure. [ 7 ]  Women commonly find it difficult to experience orgasms during  vaginal intercourse . [ 8 ] [ 9 ]   Mayo Clinic  states: "Orgasms vary in intensity, and women vary in the frequency of their orgasms and the amount of stimulation necessary to trigger an orgasm." [ 10 ]  Additionally, some women may require more than one type of sexual stimulation in order to achieve orgasm. Clitoral stimulation in normal copulation happens when the thrusting of the penis moves the  clitoral hood  and  labia minora , extending from the clitoris. [ 11 ]


Orgasm in women has typically been divided into two categories:  clitoral  and  vaginal  (or  G-spot ) orgasms. [ 12 ] [ 13 ]  70–80% of women require direct clitoral stimulation to achieve orgasm, [ 14 ] [ 15 ] [ 16 ] [ 17 ]  though indirect clitoral stimulation may also be sufficient. [ 18 ] [ 19 ]  Clitoral orgasms are easier to achieve because the  glans of the clitoris , or clitoris as a whole, has more than 8,000 sensory  nerve endings , which is as many (or more in some cases) nerve endings as are present in the human penis or  glans penis . [ 20 ] [ 21 ]  As the clitoris is  homologous  to the penis, it is the equivalent in its capacity to receive sexual stimulation. [ 14 ] [ 22 ]


Although orgasms by vaginal stimulation are more difficult to achieve, [ 13 ] [ 23 ]  the G-spot area may produce an orgasm if properly stimulated. [ 23 ]  The G-spot's existence, and existence as a distinct structure, is still under dispute, as its reported location can vary from woman to woman, appears to be nonexistent in some women, and it is hypothesized to be an extension of the clitoris and therefore the reason for orgasms experienced vaginally. [ 23 ] [ 24 ] [ 25 ]


Women are able to achieve multiple orgasms due to the fact that they generally do not require a  refractory period  like men do after the first orgasm. Although it is reported that women do not experience a refractory period and thus can experience an additional orgasm, or multiple orgasms, soon after the first orgasm, [ 26 ] [ 27 ]  some sources state that both men and women experience a refractory period because, due to clitoral hypersensitivity or sexual satisfaction, women may experience a very small period after orgasm in which further sexual stimulation does not produce excitement. [ 28 ] [ 29 ] [ 30 ]