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Naturally Selective
Researchers of human behaviour have identified an ‘orgasm gap’: Men usually orgasm during intercourse, whereas women often do not. This book addresses this mystery. The two leading explanations are either that women are “psychologically broken” - Freud’s theory – or badly designed – the “by-product theory.” However, there is a much more compelling third explanation. Evolutionary biology, anatomy, physiology, and direct sex research suggest women have evolved under their own selection pressures and orgasm is a fitness increasing consequence such selective factors. This is revealed in their patterns of orgasmic response, which are neither random, nor inexplicable. Key Features • Synthesizes decades of peer-reviewed sex research in anatomy, biology, physiology and behavior • Engagingly written based on feedback from students, peers, and interested lay folk. • Makes sense of the “orgasm gap” between men and women. • Provides a wider context of human sexual dimorphism and mutual sexual selection. • Balances sex research are one side and real-world research and practical applications.
216 pages, Paperback
Published May 1, 2024
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December 12, 2025
I like the premise of this book, as I find the byproduct theory to be disturbing, misogynistic, and rapey. I’m glad King has taken it on. Oxytocin increases 10 times more when a woman orgasms during a sexual encounter versus if she doesn’t. Acting like 1) reward for reproductive behavior and 2) extra pair bonding hormones have no evolutionary benefit when clitoral damage makes sex and relationships extremely difficult is an affront to the dignity of women.
However, it is so poorly researched and full of misinformation that it is too painful to read. Like most so called “experts” on female sexuality, King is a male psychologist who lacks spatial ability (based on his consistently incorrect descriptions of the clitoris) and can’t do math.
I say this as someone who has personally changed 20 major medical textbooks, anatomy posters, anatomy apps, online resources, board certification exams, etc., and has dissected clitorises and published an anatomic study.
Egregious errors from the pages I got through:
“The part of the clitoris that is typically visible is homologous to the glans of the penis. However, the rest of the clitoris is internal and, after an inch or two, it divides and the remainder of its erectile tissues,”
FALSE. The external clitoris is on average 1/3rd of the length of the vulva, from the anterior commissure to the clitoral frenulum. It consists of a body (shaft) formed by 2 cavernosa and is capped by a glans. You can see and feel it. Imagine if people pointed at the penile shaft and said “it’s internal!” because it is covered by its own skin. This is a harmful misrepresentation that causes women to get mutilated by doctors who cut into the clitoral body by accident due to confusion over the fact that it is right under its own skin and NOT INTERNAL.
The clitoral body (shaft) is homologous to the penile body (shaft). The clitoral glans is homologous to the penile glans. This should not be confusing.
“in common with all other primates, females are the key drivers of sexual selection, this meant studying the mechanisms of that.”
FALSE. Marmosets and tamarins have choosier males. This is also untrue of humans in harsh environments like Tibet where they have polyandrous mating systems.
“First, women (but not men) who have undergone complete spinal cord transection can still experience a type of orgasm.”
FALSE. There are countless papers on orgasm in men after spinal cord injury. As in women with SCIs, these orgasms are not the same as in people who don’t have SCIs because pudendal nerve signals obviously can’t get to the brain.
“I found that fully half the textbooks in my local specialist bookshop, which were used to train the next generation of medical students, mislabeled the clitoris as a tiny, functionless, entirely external organ.”
Implausible. As someone who has reviewed and advocated for changes to clitoral anatomy covered every major anatomy textbook used to train medical students, I want to know what textbooks he is talking about, as I have not seen a single one other than Last represent the clitoris this way. Netter, Gray, Clemente, Thieme, Sobotta, Moore, Grant, etc. have all shown the bulbs and crura since forever.
“The last time I did this, roughly half of the medical textbooks—the exact same ones that are used to train doctors and surgeons—were in disagreement with the other half. One half labeled, as if complete, a structure they called the “clitoris” as a wholly external organ, but this is really the clitoral glans—a small but highly sensitive part of the clitoris,”
FALSE. First of all, most of the external clitoris is the clitoral body (shaft), covered only by its own skin. Secondly, no surgery textbooks that I have checked exclude the internal crura (known since 1500s) or bulbs (known since 1600s). I say this having advocated for inclusion of detailed clitoral anatomy in OB/GYN surgery and plastic surgery textbooks.
“the vagus nerves provide an important sex-specific arousal path in women only.”
FALSE. The vagus nerve can carry information about genital arousal and orgasm to the brain in BOTH men and women with SCIs. But it is not involved in actually triggering arousal or orgasm. This gets wildly misrepresented all the time because of a dumb study by another male psychologist who concluded that orgasm was being triggered from cervix stimulation in women with spinal cord injuries despite the fact that he did not prove this at all. The present of a spinal cord injury above where the orgasm reflex occurs in the spinal cord does not preclude the ability to trigger an orgasm with vaginal or penile stimulation.
“there exist a variety of neural pathways in the vaginal area, including deep inside as far as the cervix, which can also trigger female orgasm, quite independent of the clitoral pathway.”
FALSE. See above.
“However, Kinsey’s response to Freud (and after him, Masters and Johnson) inspired a line of thinking that resulted in the idea that women were simply not designed by natural selection to orgasm through intercourse at all—the by-product theory.”
FALSE. First of all, Masters and Johnson actually proved how some external clitoral stimulating was mechanically inevitable with penetration. This is just basic physics. Secondly, even if women were not designed to orgasm from penetration alone (research suggests most are not) that would not prove the by-product theory.
It is perfectly plausible that a need for dedicated stimulation helped select for better partners. One study showed that if a man performs cunnilingus, it improves the woman’s likelihood of orgasm by 17 times. Performing cunnilingus is furthermore correlated with prosociality AND whether a woman orgasms at first encounter predicts the longevity of the relationship. Orgasm rate furthermore is correlated with relationship satisfaction.
“Persian anatomist Avicenna was referring to the clitoral glans as “el bathr,” the (woman’s) penis. 15 In modern medicine, the complex—and largely internal—structure of the clitoris was documented by Kobelt as early as 1851.16”
FALSE. Avicenna, like Hippocrates before him, was not a complete idiot and recognized the external clitoral body as well as the glans. Secondly, Kobelt’s book on the male and female organs of pleasure came out in 1844. It describes the clitoris better than any modern textbooks other than Di Marino (still has errors though). I translated it all on my Substack.
“In their eagerness to overturn Freud, Masters and Johnson … concluding that masturbation of the surface of the clitoral glans would generate all the sexually pertinent effects they wanted to measure. 19 They concluded that female orgasms performed no function.”
FALSE. How is this guy making up so much BS? They described the mechanism by which clitoral glans stimulation is induced via traction on the labia minora during penetration. They said all orgasms were clitoral orgasms and correctly identified glans stimulation as most critical for inducing penetrative orgasms.
“The part of the clitoris that is typically visible is homologous to the glans of the penis. However, the rest of the clitoris is internal and, after an inch or two, it divides and the remainder of its erectile tissues,”
FALSE. The external clitoris is on average 1/3rd of the length of the vulva. It consists of a body (shaft) formed by 2 cavernosa and is capped by a glans. It extends from the anterior commissure to the clitoral frenulum. This is well represented throughout 19th century medical textbooks. You can see and feel it. Imagine if people pointed at the penile shaft and said “it’s internal!” because it is covered by its own skin. This is so retarded.
“By ‘clitoris’ in this description, Gould can only mean the external part or glans, not the richly sensitive internal parts.”
The internal parts are not nearly as sensitive as the external parts. This is why, when the external parts are damaged, women lose any prior ability to orgasm from penetration alone. No one ever says, “I lost my ability to orgasm externally but I can still orgasm internally.” Happy to hear of any exceptions, but this NEVER happens among women who reach out to me after their clitorises get damaged by doctors or in childbirth. Women OFTEN say, “I lost my ability to orgasm from penetration but I can still orgasm with a vibrator” or “with extra aggressive external rubbing not previously needed.” The obvious implication is that internal parts of the clitoris alone cannot induce orgasm and direct or indirect glans stimulation is necessary for penetrative orgasms, as both Masters and Johnson and Shere Hite, knowing full well the entire structure of the clitoris, concluded.
“On the other hand, sperm are cheap. Every human ejaculation contains a quarter of a billion of them. Every second of every day there are 18,000 ejaculations and 4.4 births.”
Sperm are not that cheap. One study found that when men ejaculated daily, the average sperm per ejaculate was 54 million. That is barely above subfertile. Sperm counts furthermore did not recover to baseline levels during the 156 day recovery period. Human females meanwhile have hidden estrus and are only possible to impregnate 20% of the time. With sex every day or every other day, women can in theory get pregnant in 3 months on average. But the typical reported average is 5-6 months with a monogamous partner. THINK how many ejaculations that is. It’s at least 42, best case scenario. add to that the fact that males can’t detect a female is pregnant for the first 3 months of pregnancy. So even with the most asshole reproductive strategy possible (without slaves with their balls cut off) of banging, mate guarding, and bailing as soon as you know she’s pregnant, that’s a 6 month and 8,400,000,000 sperm investment at a minimum per birth IF the baby makes it despite your noncommittal ass. 15% of babies furthermore were killed because of such cases.
There is actually only one sex who rarely has any cost to sexual activity, and that is the human female, who has sex regardless of whether she is ovulating. Consider that human females only would have been realistically possible to impregnate at most 1/5 x 6/48 x 100% = 2.5% of the time assuming 6 months to pregnancy and therefore 9 months of dedicated ejaculations, which adds up to a lot of jizz. But for realistically about 97.5% of women’s reproductive years, they’d be pregnant, have lactational amenorhea, or not be in a fertile stage of a cycle. Thus there would be ZERO cost to sex and only benefits. Most sex, for human females, is about social bonding and wasting sperm. Males, meanwhile, straight up waste sperm all the time and live in a fantasy world of denial about this. And that is the asymmetric cost of sex actually.
“until recently, every sexual encounter carried the potential for pregnancy for a woman,”
FALSE and DELUSIONAL. Only a small fraction of sexual encounters ever carried the potential for pregnancy.
“we have data from people who have transitioned from female to male, at least hormonally, and (sometimes) even back again, taking large doses of testosterone in the process. These people have reported on their orgasms, and they universally report that orgasms in the female state are longer lasting and fuller bodied.”
I’m just going to leave this here for people to interpret however they would like.
In summary, this book is knowledge pollution. Because of all the errors I caught, I can’t exactly trust much of what he says.
He also keeps saying the clitoris is “complex.” This is so bizarre and doesn’t make any sense. The clitoris is less complex than the penis as it doesn’t have a urethra. Other than that, everything else about it is basically the same. The penis also has crura, it also has a bulb. The clitoris has two bulbs instead of one so that the vagina can get through it.
He also misrepresents sexual function in women with FGM. The key to understanding variable functionality among women with FGM is that how much of the external clitoris is removed in each type — type 1, type 2, and type 3 — varies widely. If only the glans is removed, most of the external clitoris remains. Penile glansectomy notably also does not remove the ability to orgasm, so this should be no mystery. Importantly, the center of sexual response for women with FGM is still EXTERNAL.
He also completely misrepresented Terri Conley’s research on acceptance of casual sex offers and declined to mention that the gender gap closes when safety, predicted pleasure, and reputation are controlled for. To just ignore cultural factors is egregious.
Most of the “costs” to short term mating for women are, in my opinion, caused by social stigma, which he perpetuates by endorsing sexual double standards. SDSs are empirically harmful: they are correlated with both endorsement of and perpetration of sexual violence among men as well as female sexual dysfunction and SA victimization among women.
Because the misinformation and SDSs in this book are harmful, I’m giving it 1 star and requesting a refund.
However, it is so poorly researched and full of misinformation that it is too painful to read. Like most so called “experts” on female sexuality, King is a male psychologist who lacks spatial ability (based on his consistently incorrect descriptions of the clitoris) and can’t do math.
I say this as someone who has personally changed 20 major medical textbooks, anatomy posters, anatomy apps, online resources, board certification exams, etc., and has dissected clitorises and published an anatomic study.
Egregious errors from the pages I got through:
“The part of the clitoris that is typically visible is homologous to the glans of the penis. However, the rest of the clitoris is internal and, after an inch or two, it divides and the remainder of its erectile tissues,”
FALSE. The external clitoris is on average 1/3rd of the length of the vulva, from the anterior commissure to the clitoral frenulum. It consists of a body (shaft) formed by 2 cavernosa and is capped by a glans. You can see and feel it. Imagine if people pointed at the penile shaft and said “it’s internal!” because it is covered by its own skin. This is a harmful misrepresentation that causes women to get mutilated by doctors who cut into the clitoral body by accident due to confusion over the fact that it is right under its own skin and NOT INTERNAL.
The clitoral body (shaft) is homologous to the penile body (shaft). The clitoral glans is homologous to the penile glans. This should not be confusing.
“in common with all other primates, females are the key drivers of sexual selection, this meant studying the mechanisms of that.”
FALSE. Marmosets and tamarins have choosier males. This is also untrue of humans in harsh environments like Tibet where they have polyandrous mating systems.
“First, women (but not men) who have undergone complete spinal cord transection can still experience a type of orgasm.”
FALSE. There are countless papers on orgasm in men after spinal cord injury. As in women with SCIs, these orgasms are not the same as in people who don’t have SCIs because pudendal nerve signals obviously can’t get to the brain.
“I found that fully half the textbooks in my local specialist bookshop, which were used to train the next generation of medical students, mislabeled the clitoris as a tiny, functionless, entirely external organ.”
Implausible. As someone who has reviewed and advocated for changes to clitoral anatomy covered every major anatomy textbook used to train medical students, I want to know what textbooks he is talking about, as I have not seen a single one other than Last represent the clitoris this way. Netter, Gray, Clemente, Thieme, Sobotta, Moore, Grant, etc. have all shown the bulbs and crura since forever.
“The last time I did this, roughly half of the medical textbooks—the exact same ones that are used to train doctors and surgeons—were in disagreement with the other half. One half labeled, as if complete, a structure they called the “clitoris” as a wholly external organ, but this is really the clitoral glans—a small but highly sensitive part of the clitoris,”
FALSE. First of all, most of the external clitoris is the clitoral body (shaft), covered only by its own skin. Secondly, no surgery textbooks that I have checked exclude the internal crura (known since 1500s) or bulbs (known since 1600s). I say this having advocated for inclusion of detailed clitoral anatomy in OB/GYN surgery and plastic surgery textbooks.
“the vagus nerves provide an important sex-specific arousal path in women only.”
FALSE. The vagus nerve can carry information about genital arousal and orgasm to the brain in BOTH men and women with SCIs. But it is not involved in actually triggering arousal or orgasm. This gets wildly misrepresented all the time because of a dumb study by another male psychologist who concluded that orgasm was being triggered from cervix stimulation in women with spinal cord injuries despite the fact that he did not prove this at all. The present of a spinal cord injury above where the orgasm reflex occurs in the spinal cord does not preclude the ability to trigger an orgasm with vaginal or penile stimulation.
“there exist a variety of neural pathways in the vaginal area, including deep inside as far as the cervix, which can also trigger female orgasm, quite independent of the clitoral pathway.”
FALSE. See above.
“However, Kinsey’s response to Freud (and after him, Masters and Johnson) inspired a line of thinking that resulted in the idea that women were simply not designed by natural selection to orgasm through intercourse at all—the by-product theory.”
FALSE. First of all, Masters and Johnson actually proved how some external clitoral stimulating was mechanically inevitable with penetration. This is just basic physics. Secondly, even if women were not designed to orgasm from penetration alone (research suggests most are not) that would not prove the by-product theory.
It is perfectly plausible that a need for dedicated stimulation helped select for better partners. One study showed that if a man performs cunnilingus, it improves the woman’s likelihood of orgasm by 17 times. Performing cunnilingus is furthermore correlated with prosociality AND whether a woman orgasms at first encounter predicts the longevity of the relationship. Orgasm rate furthermore is correlated with relationship satisfaction.
“Persian anatomist Avicenna was referring to the clitoral glans as “el bathr,” the (woman’s) penis. 15 In modern medicine, the complex—and largely internal—structure of the clitoris was documented by Kobelt as early as 1851.16”
FALSE. Avicenna, like Hippocrates before him, was not a complete idiot and recognized the external clitoral body as well as the glans. Secondly, Kobelt’s book on the male and female organs of pleasure came out in 1844. It describes the clitoris better than any modern textbooks other than Di Marino (still has errors though). I translated it all on my Substack.
“In their eagerness to overturn Freud, Masters and Johnson … concluding that masturbation of the surface of the clitoral glans would generate all the sexually pertinent effects they wanted to measure. 19 They concluded that female orgasms performed no function.”
FALSE. How is this guy making up so much BS? They described the mechanism by which clitoral glans stimulation is induced via traction on the labia minora during penetration. They said all orgasms were clitoral orgasms and correctly identified glans stimulation as most critical for inducing penetrative orgasms.
“The part of the clitoris that is typically visible is homologous to the glans of the penis. However, the rest of the clitoris is internal and, after an inch or two, it divides and the remainder of its erectile tissues,”
FALSE. The external clitoris is on average 1/3rd of the length of the vulva. It consists of a body (shaft) formed by 2 cavernosa and is capped by a glans. It extends from the anterior commissure to the clitoral frenulum. This is well represented throughout 19th century medical textbooks. You can see and feel it. Imagine if people pointed at the penile shaft and said “it’s internal!” because it is covered by its own skin. This is so retarded.
“By ‘clitoris’ in this description, Gould can only mean the external part or glans, not the richly sensitive internal parts.”
The internal parts are not nearly as sensitive as the external parts. This is why, when the external parts are damaged, women lose any prior ability to orgasm from penetration alone. No one ever says, “I lost my ability to orgasm externally but I can still orgasm internally.” Happy to hear of any exceptions, but this NEVER happens among women who reach out to me after their clitorises get damaged by doctors or in childbirth. Women OFTEN say, “I lost my ability to orgasm from penetration but I can still orgasm with a vibrator” or “with extra aggressive external rubbing not previously needed.” The obvious implication is that internal parts of the clitoris alone cannot induce orgasm and direct or indirect glans stimulation is necessary for penetrative orgasms, as both Masters and Johnson and Shere Hite, knowing full well the entire structure of the clitoris, concluded.
“On the other hand, sperm are cheap. Every human ejaculation contains a quarter of a billion of them. Every second of every day there are 18,000 ejaculations and 4.4 births.”
Sperm are not that cheap. One study found that when men ejaculated daily, the average sperm per ejaculate was 54 million. That is barely above subfertile. Sperm counts furthermore did not recover to baseline levels during the 156 day recovery period. Human females meanwhile have hidden estrus and are only possible to impregnate 20% of the time. With sex every day or every other day, women can in theory get pregnant in 3 months on average. But the typical reported average is 5-6 months with a monogamous partner. THINK how many ejaculations that is. It’s at least 42, best case scenario. add to that the fact that males can’t detect a female is pregnant for the first 3 months of pregnancy. So even with the most asshole reproductive strategy possible (without slaves with their balls cut off) of banging, mate guarding, and bailing as soon as you know she’s pregnant, that’s a 6 month and 8,400,000,000 sperm investment at a minimum per birth IF the baby makes it despite your noncommittal ass. 15% of babies furthermore were killed because of such cases.
There is actually only one sex who rarely has any cost to sexual activity, and that is the human female, who has sex regardless of whether she is ovulating. Consider that human females only would have been realistically possible to impregnate at most 1/5 x 6/48 x 100% = 2.5% of the time assuming 6 months to pregnancy and therefore 9 months of dedicated ejaculations, which adds up to a lot of jizz. But for realistically about 97.5% of women’s reproductive years, they’d be pregnant, have lactational amenorhea, or not be in a fertile stage of a cycle. Thus there would be ZERO cost to sex and only benefits. Most sex, for human females, is about social bonding and wasting sperm. Males, meanwhile, straight up waste sperm all the time and live in a fantasy world of denial about this. And that is the asymmetric cost of sex actually.
“until recently, every sexual encounter carried the potential for pregnancy for a woman,”
FALSE and DELUSIONAL. Only a small fraction of sexual encounters ever carried the potential for pregnancy.
“we have data from people who have transitioned from female to male, at least hormonally, and (sometimes) even back again, taking large doses of testosterone in the process. These people have reported on their orgasms, and they universally report that orgasms in the female state are longer lasting and fuller bodied.”
I’m just going to leave this here for people to interpret however they would like.
In summary, this book is knowledge pollution. Because of all the errors I caught, I can’t exactly trust much of what he says.
He also keeps saying the clitoris is “complex.” This is so bizarre and doesn’t make any sense. The clitoris is less complex than the penis as it doesn’t have a urethra. Other than that, everything else about it is basically the same. The penis also has crura, it also has a bulb. The clitoris has two bulbs instead of one so that the vagina can get through it.
He also misrepresents sexual function in women with FGM. The key to understanding variable functionality among women with FGM is that how much of the external clitoris is removed in each type — type 1, type 2, and type 3 — varies widely. If only the glans is removed, most of the external clitoris remains. Penile glansectomy notably also does not remove the ability to orgasm, so this should be no mystery. Importantly, the center of sexual response for women with FGM is still EXTERNAL.
He also completely misrepresented Terri Conley’s research on acceptance of casual sex offers and declined to mention that the gender gap closes when safety, predicted pleasure, and reputation are controlled for. To just ignore cultural factors is egregious.
Most of the “costs” to short term mating for women are, in my opinion, caused by social stigma, which he perpetuates by endorsing sexual double standards. SDSs are empirically harmful: they are correlated with both endorsement of and perpetration of sexual violence among men as well as female sexual dysfunction and SA victimization among women.
Because the misinformation and SDSs in this book are harmful, I’m giving it 1 star and requesting a refund.
March 4, 2025
I really enjoyed this book, about a somewhat controversial topic. The writing is crisp and lively and this carries you through some of the more technical parts of the book that concern evolution. Really thought-provoking read.
September 1, 2025
androcratic
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