Editing Orgasm (section)

=== Fertility ===

There are theories that the female orgasm might increase fertility.<ref name="Geoffrey Miller" /><ref name="Lloyd" /><ref name="Gould" /> For example, it has been suggested that the 30 percent reduction in the size of the vagina could help clench the penis (much like, or perhaps caused by, the [[pubococcygeus muscle]]s), which would make it more stimulating for the male (thus ensuring faster or more voluminous ejaculation). The British biologists Baker and Bellis have suggested that the female orgasm may have a [[peristalsis]] or "upsuck" action (similar to the [[esophagus]]' ability to swallow when upside down), resulting in the retaining of favorable sperm and making conception more likely.<ref>{{cite journal |doi = 10.1006/anbe.1993.1272 |last1 = Baker |first1 = R. R. |last2 = Bellis |first2 = M. A. |date = 1993 |title = Human sperm competition: Ejaculate manipulation by females and a function for the female orgasm |journal = Animal Behaviour |volume = 46 |issue = 5 |pages = 887–909 |s2cid = 53165064 }}</ref> They posited a role of female orgasm in [[Human sperm competition|sperm competition]].

The observation that women tend to reach orgasm more easily when they are ovulating also has led to the suggestion that it is tied to increasing fertility.<ref>{{cite news |first = David |last = Adam |url = https://www.theguardian.com/science/2005/jun/08/genetics.research |department = Science |date = June 8, 2005 |title = Female orgasm all in the genes |newspaper = [[The Guardian]] |url-status = live |archive-url = https://web.archive.org/web/20170302095146/https://www.theguardian.com/science/2005/jun/08/genetics.research |archive-date = March 2, 2017 }}</ref> Evolutionary biologist Robin Baker argues in ''[[Sperm Wars]]'' that occurrence and timing of orgasms are all a part of the female body's unconscious strategy to collect and retain sperm from more evolutionary fit men.<ref>{{Cite book |last = Baker |first = Robin |title = Sperm Wars: Infidelity, Sexual Conflict, and Other Bedroom Battles |publisher = Basic Books |date = 2006 |isbn = 1-56025-848-9 }}</ref> This theory suggests that an orgasm during intercourse functions as a bypass button to a woman's natural cervical filter against sperm and pathogens, and that an orgasm before functions to strengthen the filter.

Desmond Morris proposed that orgasm might facilitate conception by exhausting the female and keeping her horizontal, thus preventing the sperm from leaking out. This possibility sometimes called the "Poleaxe Hypothesis" or the "Knockout Hypothesis",  is now considered unlikely. A 1994 [[TLC (TV channel)|Learning Channel]] documentary on sex had fiber optic cameras inside the vagina of a woman while she had sexual intercourse. During her orgasm, her pelvic muscles contracted and her [[Vaginal portion of cervix|cervix]] repeatedly dipped into a pool of semen in the [[vaginal fornix]], which might ensure that sperm would proceed by the [[external orifice of the uterus]], making conception more likely.<ref>{{cite video |people = [[Desmond Morris]] (host) |date = 1994 |title = [[The Human Animal (TV series)|The Human Animal]] |medium = TV |publisher = The Learning Channel }}</ref>

Evolutionary psychologists Christopher Ryan and Cacilda Jethá, in their discussion of the female orgasm, address how long it takes for females to achieve orgasm compared to males, and females' ability to have multiple orgasms, hypothesizing how especially well suited to multiple partners and [[insemination]] this is. They quote [[primate sexuality]] specialist Alan Dixson in saying that the monogamy-maintenance explanation for female orgasm "seems far-fetched" because "females of other primate species, and particularly those with multimale-multifemale [promiscuous] mating systems such as macaques and chimpanzees, exhibit orgasmic responses in the absence of such bonding or the formation of stable family units." On the other hand, Dixson states that "Gibbons, which are primarily monogamous, do not exhibit obvious signs of female orgasm."<ref name="Ryan">{{cite book |title = Sex at Dawn |isbn = 978-0-06-220794-4 |publisher = HarperCollins |date = 2012 |page = 263 |last1 = Ryan |first1 = Christopher |first2 = Cacilda |last2 = Jethá }}</ref>

The [[female promiscuity]] explanation of female sexuality was echoed at least 12 years earlier by other evolutionary biologists, and there is increasing scientific awareness of the female [[proceptive phase]].<ref>{{cite news |last = Browne |first = Anthony |url = https://www.theguardian.com/uk/2000/sep/03/anthonybrowne.theobserver |title = Women are promiscuous, naturally |department = UK News |date = September 2, 2000 |newspaper = [[The Guardian]] |url-status = live |archive-url = https://web.archive.org/web/20160304225027/http://www.theguardian.com/uk/2000/sep/03/anthonybrowne.theobserver |archive-date = March 4, 2016 }}</ref> Though Dixson classifies humans as mildly polygynous in his survey of primate sexuality, he appears to have doubts, when he writes, "One might argue that ... the female's orgasm is rewarding, increases her willingness to copulate with a variety of males rather than one partner, and thus promotes sperm competition." Ryan and Jethá use this as evidence for their theory that [[partible paternity]] and promiscuity was common for early modern humans.<ref name="Ryan" />