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Evolution and Human Sexual Behavior
Few things come more naturally to us than sex or so it would seem. Yet to a chimpanzee, the sexual practices and customs we take for granted would appear odd indeed. He or she might wonder why we bother with inconveniences like clothes, why we prefer to make love on a bed, and why we fuss so needlessly over privacy. "Evolution and Human Sexual Behavior" invites us into the thought-experiment of imagining human sex from the vantage point of our primate cousins, in order to underscore the role of evolution in shaping all that happens, biologically and behaviorally, when romantic passions are aroused.
Peter Gray and Justin Garcia provide an interdisciplinary synthesis that draws on the latest discoveries in evolutionary theory, genetics, neuroscience, comparative primate research, and cross-cultural sexuality studies. They are our guides through an exploration of the patterns and variations that exist in human sexuality, in chapters covering topics ranging from the evolution of sex differences and reproductive physiology to the origins of sexual play, monogamous unions, and the facts and fictions surrounding orgasm.
Intended for generally curious readers of all stripes, this up-to-date, one-volume survey of the evolutionary science of human sexual behavior explains why sexuality has remained a core fascination of human beings throughout time and across cultures.
Peter Gray and Justin Garcia provide an interdisciplinary synthesis that draws on the latest discoveries in evolutionary theory, genetics, neuroscience, comparative primate research, and cross-cultural sexuality studies. They are our guides through an exploration of the patterns and variations that exist in human sexuality, in chapters covering topics ranging from the evolution of sex differences and reproductive physiology to the origins of sexual play, monogamous unions, and the facts and fictions surrounding orgasm.
Intended for generally curious readers of all stripes, this up-to-date, one-volume survey of the evolutionary science of human sexual behavior explains why sexuality has remained a core fascination of human beings throughout time and across cultures.
376 pages, Hardcover
First published February 1, 2013
17 people are currently reading
172 people want to read
About the author
Peter B. Gray
4 books8 followersI have a passion for understanding various aspects of human reproduction from an integrative, evolutionary perspective. That's a sensible scholarly passion too: in a Darwinian world, the ultimate currency is reproductive success.
My academic training as an undergraduate was at UCLA, where I majored in Anthropology and Geography/Environmental Studies. While I began as a Civil Engineering student, one Anthropology class threw me off those tracks and on to this other. The faculty were inspiring, and so were study abroad experiences in Kenya and Costa Rica, which prompted my non-stop mental application of the same evolutionary principles applied to other creatures to us as well.
I earned a PhD in 2003 in Biological Anthropology at Harvard University. Faculty mentors reinforced the importance of viewing human behavior, physiology, and health within an overarching evolutionary framework. Comparison with other primates is illuminating, an international scope is important, and so is appreciation of the complementary ways that ultimate and proximate processes play.
I subsequently bulked up my clinical research and androgen side through a postdoc in Los Angeles, at a time when my wife and I also welcomed our first daughter amidst kin support. Reproductive ideas and realities have been enmeshed ever since. And since 2005 I have been an anthropology professor at the University of Nevada, Las Vegas (UNLV), allowing space for research, thinking, and teaching on these same passions.
My academic training as an undergraduate was at UCLA, where I majored in Anthropology and Geography/Environmental Studies. While I began as a Civil Engineering student, one Anthropology class threw me off those tracks and on to this other. The faculty were inspiring, and so were study abroad experiences in Kenya and Costa Rica, which prompted my non-stop mental application of the same evolutionary principles applied to other creatures to us as well.
I earned a PhD in 2003 in Biological Anthropology at Harvard University. Faculty mentors reinforced the importance of viewing human behavior, physiology, and health within an overarching evolutionary framework. Comparison with other primates is illuminating, an international scope is important, and so is appreciation of the complementary ways that ultimate and proximate processes play.
I subsequently bulked up my clinical research and androgen side through a postdoc in Los Angeles, at a time when my wife and I also welcomed our first daughter amidst kin support. Reproductive ideas and realities have been enmeshed ever since. And since 2005 I have been an anthropology professor at the University of Nevada, Las Vegas (UNLV), allowing space for research, thinking, and teaching on these same passions.
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November 17, 2013
This book was awesome. Answered some questions that I have been wondering for a long, long time. Also easy to read and easy to understand. Quick--doesn't suffer from the "too much info" problem so many books do. There was a ton of stuff that was same-old info I have heard before. But there was also a ton of fabulous new things I didn't know--here are my favorites:
-If you give a female lemur hormonal contraception she will no longer be attractive to lemur males.
-There is substantial evidence that humans, by nature, are monogamous with some polygamy. There are many factors that lead the authors to this conclusion, one is the size difference between men and women: the more polygamous a species, the greater the size difference between the male and female. The more monogamous, the closer in size the male and female are. Another factor is sperm count. Humans have relatively low sperm count which means a guys sperm probably wont have to be competing with another guys sperm to fertilize the egg.
-Many mammals commit infanticide if they don't think it is a good time to raise a child, humans included. The main reason human women commit infanticide is uncertain paternal investment i.e. they know they can't raise the baby alone. Other big reasons are low infant quality (birth defects) and twins (where a female cannot afford to care for both).
-Almost all humans will engage in same-sex sexual activity if that is the only sex that is available to them. Heterosexual guys in prison will have sex with men. Heterosexual concubines living in a large harem will have sex with women. There were many other examples but I can't remember them off the top of my head.
-Female hunter-gatherers are ready to be married when they are around 18. They are proficient enough at gathering and are capable of raising offspring. Male hunter-gatherers are ready to be marred around 25 to 30. Building strength and learning to hunt so you can provide for a family takes a longer. What ends up happening is that young female hunter-gatherers get their sexual needs met in marriage. The male hunter-gatherers have sexual needs but no one to have sex with since the girls their age have married older guys who can provide them with meat. Different societies had different solutions to this problem that, over the years, became culturally ingrained. In quite a few societies older men (possibly because their wives were breast feeding and uninterested in sex) would have sex with the younger men. In other societies post-menopausal women would have sex with the younger men. Over time these practices become highly ritualized with lots of rules and customs to follow. I FINALLY UNDERSTAND ANCIENT GREECE!!!!!! Another way the older males of a society dealt with the 15-25 year olds who kept trying to seduce their wives was to ship them off to war.
-Ancient pottery shows pictures of women holding babies while having sex
-In hunter-gatherer societies, children practice having sex with one another, so do young (infertile) teenagers. This is an expected part of development and preparation for adult life. All monkeys do this as well. Chimpanzees require sexual learning as part of childhood or they wont be able to mate properly when they are grown.
-In almost all societies the sexual practices of children mimic those of the adults--our society is quite strange that we expect our children not to have any sexuality whatsoever.
-Orangutans are known to grab at and and attempt to sexually molest human researchers.
-Nursing offspring (humans and monkeys) will try to prevent their mom from mating--it is crucial for their survival. Since humans used to nurse for 4+ years it makes sense for human children to protest when they see their mother engaging in mating activity (like kissing their dad). Makes so much more sense than Freud's theory.
-Incest taboos began so that societies had access to the resources of others. These taboos exist in most societies. But science shows that incest among first cousins will only increase mortality of offspring by 4%.
-The youth culture we see now would not exist if women still got married and had families soon after they got their periods.
-The Lepcha of India expect girls to have sex by the time they are 11 or 12. It is thought that this is what makes puberty start.
-Human males have small sperm reservoirs, suggesting that human males were designed to ejaculate a couple times a week rather than daily.
-When Asians first saw Europeans kissing they thought it was disgusting.
-There is a notable lack of loud coital vocalizations in the cross-cultural record. It is a fact though that female vocalizations of pleasure will make a male come faster.
-Women's vaginas will "lube up" for sex whether the woman is into it or not. The vagina must do this to protect itself from tearing and other damage.
-Evolutionarily the authors disagree with the idea of sexual dysfunction. They "disagree with the very notion of classifying variation as dysfunction." The average postpartum women will be severely "sexually dysfunctional" by the current definition. The authors disagree with defining what is normal as dysfunctional.
-Hunter-gatherer women will not get their periods for almost 2 years after the birth of a baby. (Depends on how many calories are available to them though)
-The only reason human live past 50 (past making sure their offspring survive) is to help care for their grandchildren. Diminished interest and ability to have sex is adaptive. Older folks are supposed to use their energy to care for their grandkids, not mating. The presence of a grandparent helping to care for the kids is positively associated with survival of children. *Hunter-Gatherer Childhoods addresses this much better than this book (in more depth and this book claims it is only grandmothers while HG Childhoods shows that is not the whole story).
-In some societies it is even taboo for a married couple to continue having sex after all their children are married. Their priorities should be elsewhere.
-The word testimony refers to the practice of holding a man's testicle in your hand while making an oath.
-Today about 1/3 of Americans are single. Just 100 years ago it was aberrant to be single and single people were treated as inferiors.
January 3, 2023
ما هي الفوائد التكيفية للتكاثر الجنسي؟
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قبل أن نتكلم عن الفوائد ، دعونا نجيب على سؤال : ما هي تكاليف التكاثر الجنسي؟
نلاحظ زيادة التكاليف كلما شهدنا زيادة في معدل وفيات الذكور (وفيات مرتبطة بمنافسات التزاوج ، مثل ما يحدث للمراهقين عندما يفعلون أشياء تقلل من احتمالات بقائهم على قيد الحياة) أو ، بشكل أقل دراماتيكية ، التكاليف الروتينية للتودد البشري المعاصر : أموال تُنفق على أشياء مثل الزهور والشوكولاتة والمجوهرات والليالي الرومانسية بالخارج أو النفقات الأخرى للبحث عن شركاء جنسيين.
لولا الحاجة إلى التكاثر الجنسي ، لما كانت الكائنات الحية ، بما في ذلك البشر ، بحاجة إلى تكريس الوقت والجهد للبحث عن رفقاء ومغازلتهم وإعالتهم. لولا الحاجة إلى التكاثر الجنسي ، لكانت الكائنات الحية ، بما في ذلك البشر ، أقل عرضة للانخراط في منافسة مع أفراد من نفس الجنس للحصول على شركاء جنسيين ، وهي منافسة يمكن أن تتراوح من المشاحنات الخفيفة إلى العدوان الجسدي القاتل . كل هذا يندرج تحت بند واحد : تكاليف أكثر ملذات الحياة بدائية ، وتعقيدًا ، وأساسية : الجنس.
التكلفة الرئيسية الأخرى للتكاثر الجنسي هي خسارة نصف تراثك الجيني. يتطلب التكاثر الجنسي أن تختلط الأمشاج (النطاف والبويضات) مع تلك الموجودة في كائن حي آخر لإنتاج نسل يحمل كلاً من تراثك الجيني وتراث شريكك. وبالتالي ، يعمل التكاثر الجنسي بشكل فعال كضريبة ملكية بنسبة 50 في المائة على الإرث الجيني للفرد ، وهي تكلفة كبيرة عليك ككائن حي. لمثل هذه التكاليف ، يجب أن تحصل الكائنات الحية بالتأكيد على فوائد كبيرة ، ولكن ما هي؟
في الواقع ، يوفر التكاثر الجنسي العديد من الفوائد المحتملة الرئيسية . أحدها أنه يمكن التخلص من الطفرات الضارة (التغييرات في الشفرة الجينية). بعبارة أخرى ، يمكن للتكاثر الجنسي أن يأخذ طفرات ضارة ، ويخلط بينها ، وينتج عن ذلك نسل قد يمتلك تلك الطفرة أو لا يمتلكها. بدون هذا الخلط ، فإن الكائن الحي الذي يتكاثر لاجنسيًا سيظل عالقًا بنقل الطفرة الضارة إلى نسله ، ربما حتى زوال نسبه.
فائدة أخرى هي توليد التجديد . يتيح التكاثر الجنسي خلط التركيبات الجينية ، وإنشاء مجموعات جديدة قد تكون مفيدة في مواجهة الضغوط الانتقائية المتغيرة. من المؤكد أن عملية الخلط هذه تؤثر أيضاً على التركيبات الجينية الرابحة ، ولكن يمكن تعويض هذه التكلفة بفوائد التجديد .
تخيّل أنك حيوان يواجه بيئة طبيعية جديدة ، مما يعرضك للاختلافات في درجة الحرارة ، وهطول الأمطار ، والحيوانات المفترسة ، والأمراض ، وعوامل بيئية أخرى. قد يتيح التكاثر الجنسي التكيّف لمواجهة هذه الضغوط البيئية الجديدة. لا يعرف جينوم الكائن الحي ما هي المساهمات الجينية الأنسب للبيئة الجديدة ، لذا فإن إنتاج مجموعة متنوعة جديدة من التوليفات قد ينتج عنه خلطات تجعل أحد الكائنات الحية أكثر تكيفًا من الآخر. كدليل على هذا السيناريو الافتراضي ، لدينا مثال من بعض الأنواع ، مثل حشرات المن (قمل النبات) ، التي تتأرجح بين التكاثر الجنسي واللاجنسي ، فهي تحتفظ بالتكاثر الجنسي للأوقات التي يجب أن يتعاملوا فيها مع أكبر قدر من عدم اليقين البيئي .
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Gray Peter & Justin Garcia
Evolution And Human Sexual Behaviour
Translated By #Maher_Razouk
.
.
قبل أن نتكلم عن الفوائد ، دعونا نجيب على سؤال : ما هي تكاليف التكاثر الجنسي؟
نلاحظ زيادة التكاليف كلما شهدنا زيادة في معدل وفيات الذكور (وفيات مرتبطة بمنافسات التزاوج ، مثل ما يحدث للمراهقين عندما يفعلون أشياء تقلل من احتمالات بقائهم على قيد الحياة) أو ، بشكل أقل دراماتيكية ، التكاليف الروتينية للتودد البشري المعاصر : أموال تُنفق على أشياء مثل الزهور والشوكولاتة والمجوهرات والليالي الرومانسية بالخارج أو النفقات الأخرى للبحث عن شركاء جنسيين.
لولا الحاجة إلى التكاثر الجنسي ، لما كانت الكائنات الحية ، بما في ذلك البشر ، بحاجة إلى تكريس الوقت والجهد للبحث عن رفقاء ومغازلتهم وإعالتهم. لولا الحاجة إلى التكاثر الجنسي ، لكانت الكائنات الحية ، بما في ذلك البشر ، أقل عرضة للانخراط في منافسة مع أفراد من نفس الجنس للحصول على شركاء جنسيين ، وهي منافسة يمكن أن تتراوح من المشاحنات الخفيفة إلى العدوان الجسدي القاتل . كل هذا يندرج تحت بند واحد : تكاليف أكثر ملذات الحياة بدائية ، وتعقيدًا ، وأساسية : الجنس.
التكلفة الرئيسية الأخرى للتكاثر الجنسي هي خسارة نصف تراثك الجيني. يتطلب التكاثر الجنسي أن تختلط الأمشاج (النطاف والبويضات) مع تلك الموجودة في كائن حي آخر لإنتاج نسل يحمل كلاً من تراثك الجيني وتراث شريكك. وبالتالي ، يعمل التكاثر الجنسي بشكل فعال كضريبة ملكية بنسبة 50 في المائة على الإرث الجيني للفرد ، وهي تكلفة كبيرة عليك ككائن حي. لمثل هذه التكاليف ، يجب أن تحصل الكائنات الحية بالتأكيد على فوائد كبيرة ، ولكن ما هي؟
في الواقع ، يوفر التكاثر الجنسي العديد من الفوائد المحتملة الرئيسية . أحدها أنه يمكن التخلص من الطفرات الضارة (التغييرات في الشفرة الجينية). بعبارة أخرى ، يمكن للتكاثر الجنسي أن يأخذ طفرات ضارة ، ويخلط بينها ، وينتج عن ذلك نسل قد يمتلك تلك الطفرة أو لا يمتلكها. بدون هذا الخلط ، فإن الكائن الحي الذي يتكاثر لاجنسيًا سيظل عالقًا بنقل الطفرة الضارة إلى نسله ، ربما حتى زوال نسبه.
فائدة أخرى هي توليد التجديد . يتيح التكاثر الجنسي خلط التركيبات الجينية ، وإنشاء مجموعات جديدة قد تكون مفيدة في مواجهة الضغوط الانتقائية المتغيرة. من المؤكد أن عملية الخلط هذه تؤثر أيضاً على التركيبات الجينية الرابحة ، ولكن يمكن تعويض هذه التكلفة بفوائد التجديد .
تخيّل أنك حيوان يواجه بيئة طبيعية جديدة ، مما يعرضك للاختلافات في درجة الحرارة ، وهطول الأمطار ، والحيوانات المفترسة ، والأمراض ، وعوامل بيئية أخرى. قد يتيح التكاثر الجنسي التكيّف لمواجهة هذه الضغوط البيئية الجديدة. لا يعرف جينوم الكائن الحي ما هي المساهمات الجينية الأنسب للبيئة الجديدة ، لذا فإن إنتاج مجموعة متنوعة جديدة من التوليفات قد ينتج عنه خلطات تجعل أحد الكائنات الحية أكثر تكيفًا من الآخر. كدليل على هذا السيناريو الافتراضي ، لدينا مثال من بعض الأنواع ، مثل حشرات المن (قمل النبات) ، التي تتأرجح بين التكاثر الجنسي واللاجنسي ، فهي تحتفظ بالتكاثر الجنسي للأوقات التي يجب أن يتعاملوا فيها مع أكبر قدر من عدم اليقين البيئي .
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Gray Peter & Justin Garcia
Evolution And Human Sexual Behaviour
Translated By #Maher_Razouk
September 19, 2025
If you have lots of time to waste, a quick search under "sex" or similar keywords on YouTube quickly turns up a plethora of videos explaining attraction and sexual behavior in humans (and if your tolerance for misogyny is high, you can also explore "pick-up advisors," whose content ranges from the mild to the deeply offensive--some of whom are women who promise to reveal the secrets of getting women into bed). None of this content is very useful to anyone who actually wants to understand the evolutionary argument about how we came to have the behaviors we embody. In Evolution and Human Sexual Behavior Peter B. Gray and Justin R. Garcia promise to explore, in depth, the science of sexual evolution.
This isn't an easy field, and the contentions among researchers are considerable. Gray and Garcia wade through it all. Some of what they have to say is illuminating and useful; some, not so much. I was especially frustrated at their lack of treatment of social and cultural factors. The range of human sexual behavior seen through ethnographic lenses is quite wide, but they mostly don't talk about that. They also have an annoying tendency to treat modern-day hunter-gatherers as if their cultures were frozen in time from (I suppose) the Pleistocene, a fallacy long ago smashed by anthropologists.
Read critically, Evolution and Human Sexual Behavior offers insight into certain aspects of our sexuality, but only via certain approaches. It's hardly the last word.
This isn't an easy field, and the contentions among researchers are considerable. Gray and Garcia wade through it all. Some of what they have to say is illuminating and useful; some, not so much. I was especially frustrated at their lack of treatment of social and cultural factors. The range of human sexual behavior seen through ethnographic lenses is quite wide, but they mostly don't talk about that. They also have an annoying tendency to treat modern-day hunter-gatherers as if their cultures were frozen in time from (I suppose) the Pleistocene, a fallacy long ago smashed by anthropologists.
Read critically, Evolution and Human Sexual Behavior offers insight into certain aspects of our sexuality, but only via certain approaches. It's hardly the last word.
April 25, 2021
Loads of great information, very interesting and easy to read, while being well-researched
January 12, 2014
This book is great. A good level of information density, fascinating information and the occasional pinch of delightful dry humour. If indeed, "evolution and human sexual behavior" is a topic on interest to you, read. this. book. (If you don't have any biology background you might want to gloss over the dirty details of the endocrine system, but it's all good).
I found it interesting that in both the intro and conclusion of the book Gray and Garcia slam the recent popular book "Sex at Dawn" has an incorrect message (i.e. that recent human evolutionary history is characterized by promiscuity, as opposed to slight polygyny/mostly monogamy, and therefore we should all be more promiscuous and give up long-term pair bonds). While I'm sure Gray and Garcia make a much stronger, evidenced-based case for mostly-monogamous long-term pair bonding, I am interested to read "Sex at Dawn" to see how strongly their opinion is, and indeed if they argue to justify promiscuous behavior as opposed to just not-strictly-monogamous behavior. I'll update this if/when I read "Sex at Dawn".
UPDATE!
So apparently there's already a book called "Sex at Dusk" which tears down everything that's wrong with "Sex at Dawn". My impression is that "Dusk" is required antidote reading for "Dawn", but seriously just save yourself the time and read "Evolution and Human Sexual Behavior".
I found it interesting that in both the intro and conclusion of the book Gray and Garcia slam the recent popular book "Sex at Dawn" has an incorrect message (i.e. that recent human evolutionary history is characterized by promiscuity, as opposed to slight polygyny/mostly monogamy, and therefore we should all be more promiscuous and give up long-term pair bonds). While I'm sure Gray and Garcia make a much stronger, evidenced-based case for mostly-monogamous long-term pair bonding, I am interested to read "Sex at Dawn" to see how strongly their opinion is, and indeed if they argue to justify promiscuous behavior as opposed to just not-strictly-monogamous behavior. I'll update this if/when I read "Sex at Dawn".
UPDATE!
So apparently there's already a book called "Sex at Dusk" which tears down everything that's wrong with "Sex at Dawn". My impression is that "Dusk" is required antidote reading for "Dawn", but seriously just save yourself the time and read "Evolution and Human Sexual Behavior".
July 25, 2015
This book was fantastic - I learned so much about the evolution of human reproduction. I loved the primatology and biology that was incorporated into the book. Garcia and Gray also include a considerable amount of wit and humor. I found myself turning each page and saying "No way!" each time I learned something fascinating and new. A great read for any who are interested in human sexual behavior, who feel that their sex ed in middle/high school was lacking, and for those who are curious in general about the evolution of human sexual behavior compared with that of primates.
August 18, 2016
By giving a whole host of cross-cultural, cross-generational, and cross-species observation, this well organized and well referenced book details the plasticity and diversity of sexuality, using an integrative approach that combines evolutionary, mechanistic, and social accounts. Marred only occasionally by mild academic tediousness, it is otherwise insightful and enlightening, and is indispensable to those who strives to understand rather than be indoctrinated. Four stars.
September 2, 2016
Fascinating.
Displaying 1 - 8 of 8 reviews