The Biology of Human Sexual Behavior (repeat)

What can biology tell us about human sexual behavior? What kinds of releasing stimuli lead to sexual behavior? What is the effect of pheromones, hormones, genes and our evolutionary history upon our behavior? Robert Sapolsky discusses these issues and more in a broad biological survey of human behavior that starts with an ethologists attention to understanding the behavior itself and then examines the full timeline of biological factors that lead to the behavior from the most proximal (closest) to the most distal (furthest) factors: neurology, releasing stimuli, acute and chronic hormonal situation, cultural factors, perinatal biology and environment, genetics, and the evolutionary and environmental influences.

This discussion is based on 2½ Robert Sapolsky videos totaling 4 hours of lectures. Watching the videos and reading my notes are optional, but the material is so fascinating that I invite you to delve into it and explore it more deeply noting any questions that occur to you.

Human Sexual Behavior I (1h 40m video). In this video Sapolsky introduces his approach to comprehensively explore the biology of sexual behavior. After the introduction he explores big picture issues including the scientific approach to discussing sexual behavior and the challenges of the science. Then he explores what is unique about human sexual behavior in the animal kingdom. Then he discusses the neurobiology of sex followed by its endocrinology (hormonal system). At the end he begins discussing the releasing stimuli for sexual behavior. The rest of that discussion continues in the next video. Read my extensive notes summarizing Sapolsky's discussion.

Human Sexual Behavior II (1h 40m video). In this video Sapolsky continues with the discussion about releasing stimuli for sexual behavior. Then he discusses perinatal factors, genetic effects, and the evolutionary history of human sexual behavior. Along the way we learn more about the biology of homosexuality and transexuality. Is each of us intersexual? Read my extensive notes summarizing Sapolsky's discussion.

Human Sexual Behavior III (the first 52m of a 1h 35m video). In the first half of this video, Sapolsky concludes the discussion of the evolutionary history of human sexual behavior. Read my extensive notes summarizing Sapolsky's discussion.

This topic is a repeat of the one on Sunday March 9th.

I have led several prior discussions on Robert Sapolsky whose descriptions (and videos) you may enjoy. The Uniqueness and Evolution of Humans (15 Apr 2012) is based on a commencement speech Sapolsky delivered. The other discussions have been based on Sapolsky's course BIO 250, HUMBIO 160: Human Behavioral Biology. There were two discussions on "The Evolutionary and Genetic Bases of Human Behavior" which covered videos 2-7 of the course on 14 Jul 2013 and 27 Jul 2013, two discussions on "The Biology of Learning" which covered videos 8 & 9 of the course on 10 Nov 2013 and 30 Nov 2013. There were three discussions on "Brain Science and Human Behavior" which covered videos 10-14 of the course on 12 Jan 201418 Jan 2014, and 2 Feb 2014.

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  • CJ F.

    The sports world is banning women from competition based on their natural hormonal levels. As Robert Sapolsky explained, sex identity and individual differences lead to a whole world of intersexuality (people with ambiguous sex traits). This opinion piece explains the ignorance about sexuality behind banning women with naturally high testosterone levels from sports unless they undergo potentially irreversible feminizing treatments:

    As the article points out, testosterone doesn't even appear to affect female athlete performance: "16.5 percent of the elite male athletes had testosterone in the so-called female range; nearly 14 percent of the women were above the "female" range."

    We are probably all intersexual and we should accept and honor our sexual variations, not ban unusual variations from sports!

    Where is Alice Dreger when you need her?

    1 · April 12

  • CJ F.

    I keep thinking about Sidney's comment that love was missing from our discussion on the biology of human sexual behavior. Since Sapolsky had so much interesting content, there wasn't time to address the subject in full.

    In this 23 minute video Helen Fisher outlines her vision of the biology of love (mostly in the first 10 minutes):

    She explains that the main characteristics of romantic love are an intense craving, motivation, and obsession. She argues that romantic love is not an emotion. She claims it is a drive built on three brain systems for reproduction: sex drive, romantic love, and attachment.

    Her talk is interesting. Hopefully it partially bridges the gap which Sidney's comment identified.

    2 · March 19, 2014

    • Jyoti M.

      Today I learnt why Riksha drivers in India were admired by women. No , I was not one of those women. Thanks CJ !Great video.

      1 · March 20, 2014

    • Liliya S.

      I LOVE Sidney's comment. Helen Fisher said: "...millions of years ago, we evolved three basic drives: the sex drive, romantic love and attachment to a long-term partner." And so many people are alone.

      March 22, 2014

  • Sidney

    Mucho thanks CJ for your follow-up on the subject of love as it relates to the biology of human sexual behavior, and for recommending Helen Fisher's video!

    1 · March 19, 2014

  • Ralph C

    I had a great time with wonderful conversation.
    The education, life experience, and forthrightness of everyone made the discussion thought provoking, energetic, and welcoming.

    1 · March 18, 2014

  • CJ F.

    Carin Bondar in her recently posted TED Talk explains better than Sapolsky that animal sex is far more unusual than human sex.

    March 16, 2014

  • Ginger

    Thought provoking

    1 · March 16, 2014

  • Paul S.

    Thanks to CJ and everyone for a very interesting discussion.

    1 · March 16, 2014

  • Liliya S.


    1 · March 15, 2014

  • CJ F.

    Although watching the videos is optional, I highly recommend them. There are four hours of Robert Sapolsky videos (these will provide most of the content for tomorrow's discussion):

    Human Sexual Behavior I:

    Human Sexual Behavior II:

    Human Sexual Behavior III (only first 52m):

    Here are some bonus videos.

    Isabella Rossellini's exquisite "Green Porno" series shows just how bizarre animal sex can be:
    Praying Mantis:

    Alice Dreger's remarkable perspective on intersexuality:

    Cindy Gallop: Make Love Not Porn:

    March 14, 2014

  • CJ F.

    Tomorrow's discussion on "The Biology of Human Sexual Behavior" will begin promptly at 10:30 AM.

    I imagine the discussion will run strong for 3 hours until maybe 1:30 PM or so.

    Here are the main questions that I plan to focus in on tomorrow:

    - What is unique about human sexual behavior?

    - What are the implications of the biological bases of sexual identity and orientation (homosexuality, transexuality, and intersexuality)?

    - Is there conflict between our social monogamy, sexual polygamy, the modern value of a lifelong romantic passion, and our biology?

    - Does evolutionary theory support the "battle of the sexes"? Is that OK?

    - Since humans, bonobos, and other species have non-reproductive sex, what is the biological purpose of sex?

    - What are the implications of our biological predilection for homogamy?

    Human Sexual Behavior I:

    Human Sexual Behavior II:

    Human Sexual Behavior III (only first 52m):

    March 14, 2014

  • CJ F.

    The 3rd of 3 Robert Sapolsky videos for Saturday's discussion "The Biology of Human Sexual Behavior" is at (note: only the first 52m will be discussed on Sunday).

    This video continues the discussion on the evolution of sexual behavior including homosexuality. One of the most interesting parts concerns the predilection for homogamy (mating with someone who has similar or homogeneous traits). 90% of American couples share the same religion, are within three years of each other, have the same ethnicity & race, and the socioeconomic status (SES) of their childhood. Wow! Is our sexual behavior so biased by our biology that most of us cannot mate with those who are too different from us? Sapolsky ends on a positive note: everyone wants to mate with someone who is nice to them.

    Read my notes on the video:

    Watch the first 52m of this 96m vid at

    March 13, 2014

  • CJ F.

    The 2nd of the 3 Robert Sapolsky videos for Sunday's discussion on "The Biology of Human Sexual Behavior" is at

    Since testosterone becomes estrogen to masculinize the brain (strange!?), we all start with a female brain which gets masculinized (even females whose adrenal glands produce some testosterone)? So our brains have qualities from both sexes. How much of the other sex do you have in you? Are we all intersexual (partially both male & female)?

    Evolutionists see sexual behavior as a coevolutionary "battle" between male attempts to control of female sexual behavior (chastity belts and clitorectomy) and the recent (gasp!) discovery of female choice. Is this a valid biological basis for "the battle of the sexes"? Is equality of the sexes is problematical?

    Read my notes at

    Watch the 1h 40m Part II of Sapolsky's "Human Sexual Behavior":

    March 12, 2014

  • CJ F.

    Biology has found brain nuclei (regions of neurons) that predict homosexuality and transexuality. These biological bases for homosexuality, transexuality, and intersexuality are covered in the 1st of 3 Robert Sapolsky videos at

    Are sexual identity and orientation biologically determined? Are each of us a unique composition of biological parts which we erroneously(?) think of as male or female? Should we each consider ourselves intersexual beings instead?

    Alice Dreger's TED Talk has some relevant thoughts:

    Humans have social monogamy (90% of us), but sexual polygamy (10-40% of children do not have the father they are supposed to). Marriage tends to last 2-4 years (= inter birth interval)? Is romantic passion ephemeral?

    My notes on the 1st Sapolsky video:

    Watch the video at

    March 11, 2014

  • CJ F.

    Saturday's discussion on "The Biology of Human Sexual Behavior" is based on three optional Robert Sapolsky videos. The 1st is 101m and can be watched at

    Sapolsky emphases that human sexual behavior is pretty "ordinary" by noting that many species have truly bizarre forms of sex. Here are 3 exquisite videos from Isabella Rossellini's "Green Porno" series: Earthworm , Praying Mantis , and Snail .

    Read my extensive notes at

    Sapolsky claims that what is unique about human sexual behavior is that we have 1) egalitarian sex (all adults are allowed to have sex), 2) sex in private, and 3) human males often pathologically confuse sexual behavior with violence. Maybe our sex is bizarre after all? We will critically review these claims.

    Watch Sapolsky's 101m video here:

    March 10, 2014

  • CJ F.

    A week from today, on Saturday March 15th, we will discuss "The Biology of Human Sexual Behavior" based on 2½ Robert Sapolsky videos totaling 4 hours of video lectures. Watching the videos is optional and we will explain everything in case you cannot watch the videos. But Sapolsky is exquisite, so I highly recommend watching them. Here are the three videos:

    Human Sexual Behavior I:

    Human Sexual Behavior II:

    Human Sexual Behavior III (only the first 52 minutes, the second half is on Aggression):

    March 8, 2014

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