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16. Human Sexual Behavior II — Transcript

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0:04Stanford University.
0:09Let us get started here.
0:16So, picking up from the other day, where
0:18have we gotten? Not very far. Behavior
0:21full range variability of sexual
0:24behaviors, fixed action patterns. Is
0:26this kind of dark here? No.
0:30Seeing in some ways what's interesting
0:32is the conservative nature of sexual
0:34behavior across species. Other ways, the
0:37sheer variety. Trying to make sense of
0:39what aspects of human behavior are
0:41unique. All of that. Then beginning to
0:44margin backwards, what goes on in the
0:46nervous system 1 second before sexual
0:49behavior occurs, and marching through
0:52the relevant limbic structures, some of
0:54which have strong sex differences, some
0:57of which that don't. Seeing some ways in
1:00which
1:01uh neurotransmitters in the whole world
1:03of dopamine complicates things
1:04enormously. Marching through there.
1:07Where we had then gotten to was asking,
1:10"Okay, so what sort of bits of
1:12information in the environment, what
1:14sort of ethological releasing stimuli
1:17can trigger the nervous system to do its
1:19thing?" And you've got the drill by now.
1:21So, what we had done was look at a
1:23couple of different sensory systems, and
1:25we had just started to wallow in the
1:27world of pheromones, of pheromonal
1:29communication. What we ended with was
1:32number one, the hormone dependency
1:35of generating sexually meaningful
1:38pheromones. And that business being that
1:41males have to have sufficient
1:43testosterone, females have to have
1:45ovaries on board to be producing
1:47pheromones that carry sexual meaning.
1:50What is the reason for that? The fact
1:52that a whole lot of the actual chemicals
1:54that constitute sexually meaningful
1:56pheromones are made out of some sex
1:59hormone breakdown products and the sheer
2:02bizarre ready but eventual wonderful
2:04clarity of what's up with with perfumes.
2:08Then transitioning at the very end to
2:10the business about how your endocrine
2:12status has a lot to do with your
2:14perception of pheromones from the other
2:17sex that women who are over erectomized
2:19the low estrogen levels have trouble
2:22being able to differentiate the smell of
2:25males and females men and women and
2:28estrogen replacement takes care of that
2:30the exact same thing when you take away
2:31testosterone for men and what we were
2:35just about to get to before we had to
2:37stop was one additional thing which is
2:40one's opinion about the pheromones that
2:42you are smelling.
2:44And this goes back to a literature
2:46really interesting one showing that not
2:48only are women better at differentiating
2:51between the smell of men and women
2:54gonadally intact men and women. Not only
2:57are they better at doing that around the
2:59point of ovulation but their preference
3:02for the smell of males gets more
3:04dramatic around the time of ovulation.
3:07Meanwhile over at the male end of things
3:10something rather similar in terms of
3:13what you make of the pheromones and this
3:15was a famous classic study in which
3:19women volunteers had their armpits
3:22swabbed at different points in their
3:24menstrual cycle and put into little
3:26serum sealed jars and all sorts of male
3:28volunteers sniffing them and rating
3:31their pleasantness. And what you found
3:34was on the average the odorants were
3:37rated in the unpleasant direction but
3:40they were rated as least unpleasant
3:42around the time that women are
3:43ovulating. And I think once we get past
3:46the world of armpit smells in little
3:48glass jars Uh, one can get into the more
3:51ethologically relevant world of men
3:54prefer pheromones derived from women
3:57around the time when women are
3:58ovulating. Once again, a
4:00testosterone-dependent phenomenon.
4:03What we now begin to look at are some of
4:05the physiological effects of sexual
4:08pheromones between sexes within sexes.
4:11One example you heard about in the very
4:13first lecture, which is that whole
4:15business that Wellesley effect, the
4:17ability of females of all sorts of
4:19different species, including college
4:21freshman human females, to synchronize
4:24each other's cycles. This being done
4:27with pheromones, intersexual perception
4:29of pheromones. So, the Wellesley effect.
4:32What's also shown in a number of rodent
4:34species is the pheromones, the smell of
4:37an adult female, will delay the onset of
4:41puberty of younger females.
4:44And how might one frame that? That is
4:46utterly a gene competition sort of
4:49strategy there. This is reproductive
4:51competition. If you arrest the
4:53development of the other females around
4:56you, you are going to leave more copies,
4:58et cetera.
5:00Meanwhile, a literature of intramale
5:03physiological effects. What happens to
5:05the physiology of males in various
5:07species when smelling the pheromones of
5:10other males? What you see first off is
5:12it depends on who the other guy you're
5:15smelling, the dominance rank. In lots of
5:18rodent species and some primate species
5:20as well, males are able to differentiate
5:22between smells of very high-ranking
5:24males and very low-ranking ones. And
5:26what do you know, they're not all that
5:27upset about the low-ranking ones. What
5:30do you see in terms of the physiological
5:32effects in a number of species when
5:34males are smelling the pheromones of
5:36big, healthy, strapping, androgenic
5:39other males, in some cases, it drives
5:42down their testosterone levels. They're
5:44totally physiologically intimidated,
5:47this being some great competitive
5:49strategy for males who could pump out
5:51just the right kind of suppressive
5:53pheromones. In other species, though,
5:56what you see is a sudden burst of sperm
5:58production. And what's that about?
6:01Another version of the same logic. This
6:03is a counter strategy. If males have
6:06come up, evolved the means in various
6:08rodent species to generate pheromones
6:12that will drive down testosterone levels
6:14in opponents, what males also want to
6:16have evolved was some mechanism of when
6:19smelling those sorts of pheromones to
6:21try to counter that by increasing sperm
6:23production.
6:25What we have here is a co-evolutionary
6:28arms race.
6:30Terms of interactions of pheromones
6:32between the sexes,
6:34and what I've been doing here is
6:35describing all this without making use
6:38of this. So, what you see is
6:39physiologically, when the female is the
6:41pheromone donor, and the other recipient
6:45is a female in terms of say puberty,
6:47decreasing puberty onset. And what we
6:50just saw with male as donor versus male
6:53is in some ways suppressing some
6:55endpoints testosterone, in some ways
6:57increasing sperm production.
6:59What you see in lots of rodent species,
7:02when you're looking at between genders,
7:04when males are the source of pheromones
7:07among rodents, it accelerates puberty
7:10onset in the females.
7:14And when you've got females as the
7:16donors, it increases testosterone level
7:19and sperm production in the males of
7:21lots of different species. So, all this
7:24makes wonderful, wonderful sort of
7:26sociobiological sense in terms how this
7:28should work. Elaborations on this, of
7:31course. What you also see is not only
7:34puberty onset and being regulated, you
7:36also see in all sorts of species where
7:39you can induce ovulation by sensory
7:42stimuli, what you see is the smell of a
7:46female
7:47will decrease the likelihood of induced
7:50ovulation.
7:52Female, the smell of a male will
7:54increase the likelihood of ovulation.
7:56All sorts of species that do not have
7:58automatic rhythms of ovulation cycles of
8:01that way, but rather they are induced.
8:04And one classic example of that are
8:06pigs. Pigs are inducible ovulators if
8:09you always wondered whether that's the
8:11case or not. And you can go and
8:14recreationally buy a variant of pig
8:17pheromone, this known as Boar Mate. And
8:20no doubt that's not only patent pending
8:22it, but somewhere out in the Midwest
8:23there's all sorts of TV jingles about
8:26Boar Mate. And Boar Mate is a puberty is
8:30a ovulation inducer in female
8:33boars. And involving a same male derived
8:37pheromone, which are found in truffles.
8:39Truffles which somehow have stumbled on
8:42the means to induce female pigs to
8:44ovulate. And no doubt that's
8:47explaining some very interesting
8:49interspecies interactions. So, that
8:51being another realm.
8:53Inducible physiological changes. In this
8:56case one classic demonstration of it, in
8:59this case probably pheromones of female
9:03causing an indirect measure of
9:05testosterone levels in a male. This is a
9:08classic paper and you will note that I
9:10didn't say females and males saying a
9:13female and a male. This was a classic
9:15paper in nature some 30 years ago or so,
9:18which was written by the very famous and
9:20well-known Dr. Anonymous. The author's
9:23name was not published there.
9:26And this was a researcher who did
9:29research in an unspecified hemisphere
9:32with an unspecified species, but
9:33involved long stretches of being at a
9:36research facility completely on his own
9:38in isolation from other humans and all
9:40sorts of people in the business for
9:42decades afterward have been speculating
9:44on who the author is and it's generally
9:46understood. And what this person noted
9:49was every now and then he would pick up
9:51and go to the city that was, you know, a
9:543-hour seaplane flight away or some such
9:57thing where among other things he had a
9:59highly significant significant other
10:02with a great deal of physical intimacy
10:04and all that stuff from kind of the
10:07right side of the chart. And what he
10:09noticed was what he perceived to be an
10:11extraordinary difference in what he was
10:13subjectively interpreting as
10:15testosterone-driven
10:17mood and level of energy and all of that
10:20depending on where he was. Not quite
10:23being the type of field ethologist that
10:25took blood from himself, what he did
10:26instead was take an indirect assay
10:29building on the well-known fact that
10:30testosterone has something to do with
10:32the rate of beard growth.
10:34And what he wound up doing was very soon
10:37having a razor there and every day
10:39shaving and getting the little bits of
10:41stubble and weighing it. Weighing it as
10:44an indirect assay of testosterone levels
10:46and what was shown was sit out there by
10:49himself with whatever ungulates he was
10:51obsessing over and this sort of rate of
10:53beard growth go back to the rest of the
10:56world and it does this and this square
10:57wave going on like that. This as a very
11:00and okay, what are all the confounds
11:02here? It's not clear if it was
11:04pheromones, maybe it was actually being
11:06in proximity to the newspaper in the
11:08town that he returned to now and then,
11:11maybe there was a confound of whatever
11:12aftershave he was using that was doing
11:15something or other to his testes.
11:16Nonetheless, generally interpreted as
11:18this being a really interesting indirect
11:21n equals one example of induction of
11:25physiological changes in human males by
11:28pheromones from females.
11:30So, if you ever meet Dr. Anonymous, who
11:32interestingly has been publishing papers
11:34for about 300 years or so every now and
11:36then,
11:37congratulate that individual on the
11:39research. Okay.
11:41So, pheromonal stuff. Now, elaborations
11:44of it, which you should be able to
11:45derive all on your own from some of our
11:47principles by now, which is what if, for
11:51example, you are a female donor and
11:55female recipient, and the whole logic
11:57here being decrease the likelihood of
11:59ovulation, delay the onset of puberty.
12:02What if these are siblings? If these are
12:05two sisters, and you were off and
12:07running with that one, it will not work
12:09as effectively. Easy kin selection
12:12argument. So, all sorts of aspects of
12:14relatedness, you will not have your
12:16testosterone levels driven up if you
12:18were a hamster and you were smelling
12:20your sister, all that sort of thing.
12:22That makes perfect sense by now.
12:25Okay. Now, switching over one last
12:29piece of business. Though, in terms of
12:30the pheromonal attractiveness stuff, a
12:33handful of studies showing that among
12:36homosexual men, what you have is it's
12:39the smell of men who are preferred to
12:42women, and it's when men have higher
12:44testosterone levels that they are
12:47preferred. And what we've got there is a
12:50exact same physiology and a somewhat
12:53going in the opposite direction flipping
12:56of things. That sure argues for some
12:58interesting biological underpinnings.
13:01One final thing, women not only prefer
13:04the smell of men when they around the
13:08time that they are ovulating, their
13:10noses selectively become more sensitive
13:12to such smells, and estrogen has all
13:16sorts of receptors on olfactory neurons.
13:19So, that makes sense. Okay, leaping over
13:22to other sensory systems, gustatory
13:25stimuli. This is not one of the more
13:27exciting outposts unless you are
13:28something like a giraffe, in which case
13:30you take part in what is called
13:32flehmening, a good old Germanic
13:35ethological term, which is you want all
13:38sorts of interesting reproductive
13:40information on somebody else, and you
13:42just don't have the time to sniff the
13:44air for pheromones. So, what you do is
13:46you go over and lick the individual's
13:48private parts, and suddenly you know oh
13:51so much about their personal lives. In
13:53this case, gustatory information being
13:55passed. We've already heard about
13:57examples of auditory priming, inducible
14:01ovulation in various moose-like species
14:04in the wilds of Minnesota, where what
14:07the stags have these roaring fixed
14:10action patterns, which will induce
14:13all sorts of ovulatory responses in
14:15females around.
14:17So, this is another domain. Remember
14:19also that interesting factoid, and when
14:21this was mentioned previously, that in
14:24human females, voices get a little bit
14:27higher around the time of ovulation and
14:29in a way that is detectable. Something
14:32important in terms of all this
14:33pheromonal stuff in humans, what has
14:35been shown over and over and over again
14:37is these are all subliminal processes,
14:41as in the humans are not consciously
14:43aware of, "Wow, this one smells more
14:46like my gonadally intact second cousin
14:49who was adopted away to Bolivia for a
14:51while when I was a kid." There's not the
14:53consciousness, but nonetheless, you
14:55force people to make these choices, and
14:57implicitly, you get insight into these
15:00same sort of influences.
15:02But, of course, by the time you get to
15:05uh humans, and you talk about sensory
15:08releasers and all of that, you get of
15:10course the point endlessly emphasized by
15:13Cosmo and God knows where else, that
15:15ultimately the most erogenous organ in
15:18humans is the brain. Thought as a
15:20releaser, thought as a more powerful.
15:23Humans are not a particularly olfactory
15:25species. We are not a particularly great
15:28auditory one, etc., etc. An awful lot of
15:31the sexual priming in humans coming by
15:34way of thought, bypassing this whole
15:37ethological world. Okay, more
15:40environmental factors, acute
15:42environmental factors that can affect
15:44all of this. And what you've got is a
15:47very reliable way to drive down libido
15:49is to make an organism terrified. Fear
15:52as suppressive of reproductive behavior.
15:56What you also have is extreme rage doing
15:58the same. Stress in general. Stress is
16:01interesting because what you get is a
16:03dichotomous outcome. Chronic stress, so
16:07now we're not talking about an acute
16:08stressor, but all the way back. Chronic
16:10stress is extremely suppressive of
16:13reproductive physiology and behavior,
16:15which you will be finding out when you
16:17read the relevant chapter in the zebra's
16:19book. But, what you see is short-term,
16:21there's a lot more variability,
16:23particularly among males. What you see
16:26is a lot of variability as to whether
16:29short-term stress stimulates
16:32arousal or inhibits it. And people have
16:35pointed out all sorts of horrific bits
16:38of evidence showing in circumstances of
16:41extreme arousal and stress, say, during
16:44warfare, where that produces all sorts
16:47of violent sexual behavior. No shortage
16:51of horrible historical precedents for
16:53those. Okay, so a difference between
16:55chronic stress versus acute stress, more
16:58effects around here. One final
17:00interesting bit of uh releasing
17:03stimulus, stimuli, whatever a bit of a
17:06stimulus is, and one that transcends a
17:09particular sensory system is something
17:11called the Coolidge effect. And the
17:13Coolidge effect probably accounts for
17:15like 49% of the misery encapsulated in
17:19human literature and movies and all of
17:21that. What is the Coolidge effect? In
17:24species after species after species, you
17:26take an individual who is sexually
17:29sated, which is to say that for example,
17:32you've got some male rodent who's been
17:33mating with a female rodent there and
17:35has gotten to the point where he has had
17:37enough, enough on some physiological
17:40level or some deeply emotional, what
17:43matters to me in my life for eventual
17:45sort of level. But in any case, the male
17:47is sated, has stopped having sex with
17:50the female. And what the Coolidge effect
17:52is about is you put in a different
17:55female and things start all over again.
17:58Variety as wildly stimulating of sexual
18:02arousal and the Coolidge effect sure
18:05works in humans and accounts for all
18:07sorts of misery. Coolidge, by the way,
18:09was not the scientist who first
18:10described it, but Coolidge refers to
18:12Calvin Coolidge and as far as I know,
18:15this is the only anecdote ever to occur
18:17about the guy. Something where he and
18:20his wife were being shown some chicken
18:22farm and there were breeding roosters
18:25and and when they would get
18:27sick of breeding with this
18:30pen, they would stick a new one in and
18:32Mrs. Coolidge made some sarcastic remark
18:35and he made one back and before you knew
18:38it, it was the Great Depression. So, I
18:40actually have no memory of what they
18:43said, but in terms of woodiness, you get
18:45what you can when you have Calvin
18:47Coolidge. So,
18:48okay, we hurdle on. We hurdle on here
18:51now beginning to look at an entire
18:54missing category here in my rush. Now we
18:57have what's going on with hormones,
18:58longer-term hormonal stuff. Not the
19:01hormone levels that you have influenced
19:04as a result of sexual behavior, not the
19:07hormone levels just right around the
19:09time of all this neurobiology happening,
19:12but now beginning to talk about hormone
19:15levels like over the last
19:1728 days or so in a female. And what one
19:20immediately barrels into is this issue
19:23of how much is sexual behavior in women
19:27a function of where you are in your
19:28cycle.
19:30What's the reason even to suspect that?
19:32The entire world of other species that
19:35will have females coming into estrous,
19:38coming into heat, having elevated
19:40estrogen levels only at very demarcated
19:43times of the year, and what you see is
19:45in lots of species, a large number of
19:48them in fact, what you see is you only
19:50get reproductive behavior, you only get
19:53sexual behavior in females around the
19:56time that they are ovulating. You only
19:58get active female proceptive seeking of
20:02sex around those times.
20:04By the time you get to non-human
20:05primates, it depends on the species
20:08you're looking at, but in general, it's
20:10not quite as tight of a relationship.
20:13So, if you had some rodent and
20:17you know, across a year, this was all
20:19the points of ovulation, your pattern of
20:22sexual behavior of female would look
20:24like this,
20:25uh likelihood of mating with a male. By
20:28the time you get to non-human primates,
20:30in most species, it looks more like
20:32that. It's not quite as dramatic, and
20:34thus of course the question becomes,
20:36where do humans fit on in on this?
20:39And a classic study, extremely
20:42influential, in the early '70s was the
20:44first to look at this, which was
20:46females, humans, women reporting their
20:49levels of sexual activity as well as the
20:52likelihood of orgasm per sexual bout, um
20:57if that's the right word, and where they
20:59were in the cycle.
21:01So, this is what you wound up seeing,
21:03and this by any measure, likelihood of
21:06having sex, whatever, the curve looked
21:09something like this.
21:15And what they reported was a big
21:18increase around the time of day 14, and
21:22a secondary increase around day 28. Not
21:25as large a one, and when you looked at
21:26the likelihood of orgasm, it was
21:28basically doing the same exact thing.
21:30Okay, day 14, that's just a somewhat
21:34less restricted version of the exact
21:36same phenomenon. Never down to zero, but
21:39nonetheless, this is another version of
21:41this exact same phenomenon. Libido,
21:44sexual proceptivity
21:46increasing in women, in human females
21:49around the time of ovulation.
21:51But no other species shows this one
21:55going on here. So, what's up with that?
21:57Any speculation why you had the
21:58secondary increase around day 28?
22:06Oh, come on. Somebody's got to
22:10Yes, you're right. That's exactly what
22:12they found. That's exactly what they
22:14found, and good for you feeling
22:15comfortable speaking up in class all in
22:17unison like that. Okay, what that tends
22:20to be is that women are more relaxed
22:23about fear of pregnancy around the time
22:26of their period, and thus sexual
22:28behavior increases somewhat around that
22:30point. But the thing that everybody most
22:32importantly came away with was just like
22:35every other mammal out there that has
22:38regular cycling or only seasonal ones,
22:41high estrogen is when you get the most
22:43sexual behavior. Okay, instead of high
22:46estrogen is the only time you get sexual
22:48behavior, instead, you simply get the
22:50most around then.
22:52In the years since, lots of people have
22:55done versions on the study, and it is
22:57frequently difficult to replicate this
23:00phenomenon in terms of a change in
23:02levels of sexual activity in women
23:05around the time of ovulation, what has
23:08remained very clear in the literature
23:09though, is that sexual arousal increases
23:13around the time of ovulation in women.
23:15Very
23:16reliable effect. And what that is
23:19interpreted as is behavior here may not
23:22be telling you anywhere near as much as
23:25motivation, arousal, proceptivity
23:28at that time. And that's a more pure
23:30measure of what's going on
23:31physiologically there, what's going on
23:33in the brains. Fitting with that is a
23:36very interesting literature suggesting
23:39that women act a little bit differently
23:41in terms of proceptive sexual signaling
23:44around the time of ovulation. Studies
23:47showing for example that women, as
23:50assessed by both women and men, women on
23:53the average wear more provocative
23:55clothing around the time that they are
23:57ovulating. Yes, people go and study
24:00things like this for a living. These
24:01were not big effects.
24:04But the all-time bizarre study I've ever
24:07heard of in this domain was actually
24:09published with a straight face by this
24:10guy, and he's a evolutionary
24:12psychologist, University of New Mexico,
24:15a guy named Geoffrey Miller, who
24:16reported the following and you know,
24:19what he was spending his time doing,
24:21which he reported was that around the
24:24time of ovulation, lap dancers get
24:28larger tips.
24:33Okay.
24:34That has since been
24:36since been replicated in E. coli and in
24:40various yeast species. And
24:44you know, I'm not going to try to unpack
24:46that one in any sort of way, but
24:48nonetheless, this was reported and shows
24:50you just how wonderful it could be to be
24:52a scientist. Can you imagine that money
24:55was being spent on that, your research
24:57dollars instead of strafing people in
24:59Kandahar province or something. Okay, so
25:02we have a peak there. This general issue
25:05of what does hormonal cyclicity in a
25:08time scale of weeks to months, what does
25:11that do to sexual behavior in various
25:13species? What does that do to sexual
25:14arousal, proceptivity? What are some of
25:18the building blocks of that? Estrogen,
25:20as estrogen levels go up, estrogen
25:23increases the expression of receptors
25:26for progesterone.
25:29So, you can immediately begin to piece
25:31that apart in at least two different
25:33ways. First one being estrogen, thus
25:36increasing the sensitivity in the brain.
25:38This is a brain effect. Sensitivity to
25:41progesterone, which has something to do
25:42with the rewarding aspects of sex. You
25:46can also translate that into molecular
25:49biology. Estrogen, being a steroid
25:52hormone, is going to bind to its
25:53receptor and do the whole transcription
25:56factor translocation sort of thing
25:58telling you that upstream of the gene
26:01for the progesterone receptor is a
26:04promoter that's responsive to estrogen.
26:06And estrogen receptors, you know how
26:08this one works by now.
26:10More pieces of it. Estrogen, when rising
26:13here, also increases the synthesis of
26:16oxytocin.
26:18Back to all that social bonding stuff.
26:20And what that suggests, I don't know if
26:23it has been studied, but that women will
26:26feel more affiliative with someone
26:29they've had sex with if around the time
26:31of ovulation than at other points. That
26:33is certainly the case with a vole, but
26:36that is certainly the case because they
26:38don't mate the rest of the time. And
26:40because male voles suddenly are
26:43expressive around there in terms of
26:44their feelings. Okay. So, more building
26:48blocks of it. Estrogen is not only
26:51having effects in the brain, but it's
26:52also having effects throughout the body
26:54at those times in terms of lowering the
26:56threshold of certain tactile receptors.
27:00What does that mean? That means around
27:02the time that women are ovulating,
27:05thanks to estrogen, they are more
27:07sensitive to touch. And I'm sure this
27:09has been studied in consenting hamsters,
27:12but my bet is that more sensitive to
27:14tactile stimulation in some parts of the
27:16body over others. What estrogen also is
27:19doing,
27:21as we just heard, is working on the
27:22olfactory system, lowering thresholds
27:25for detecting the smell of males. So,
27:28we've got all sorts of ways within the
27:30brain and in the periphery to bias
27:32towards more arousal at that time.
27:35Wonderful evolutionary biology, no
27:38problem at all.
27:39One additional piece of the female
27:41story, which is the effects over the
27:44course of this kind of time span, weeks
27:46to months to years or so, the effects of
27:48those androgens, those male sex hormones
27:52that females are releasing. And what you
27:54see there is that plays a role in
27:56proceptivity,
27:57increasing sexual arousal, sexual
28:00motivation.
28:02Meanwhile, on the other side of the
28:03road, we got males. And what does
28:06testosterone, testosterone over this
28:09time span, what does it have to do with
28:11sexual behavior in males?
28:13Well, on first pass, it sure looks like
28:16it has a lot to it. Lot to do with it.
28:19What sort of evidence? Initially,
28:22correlative evidence.
28:23Well, the time of year in various
28:27species where males do their mating is
28:30the time of year when testosterone
28:31levels are elevated.
28:34Over the lifespan, testosterone levels
28:36go up around puberty, and from about age
28:3930 on, very gently cascade down into
28:42alarming senescence. And what you see
28:44there is a similar profile in terms of
28:47sexual behavior. That does not tell us
28:49much. These are correlations.
28:51Furthermore, correlative studies in
28:53humans, a handful showing more sexually
28:56active men tend to have higher
28:58testosterone levels. And for what it's
29:01worth, a number of studies have
29:02documented a dramatic drop in
29:04testosterone levels in men right around
29:06the time that they become fathers.
29:10Okay, so figure that one out. Also, an
29:12increase in vasopressin levels at that
29:14time. You know how to interpret this one
29:17by now.
29:18So, we've got testosterone and higher
29:21levels of male sexual behavior going
29:23hand in hand. Are we looking at any
29:26causality here? First off, we already
29:29know about one piece of causality, which
29:31was the other day, sexual behavior in
29:34men, in males, increases testosterone
29:37levels. So, that's one reason why they
29:39may go hand in hand. In that scenario,
29:41testosterone has nothing to do with
29:44increasing the likelihood of the
29:46behavior.
29:47So, does testosterone actually have a
29:49causal role in increasing the likelihood
29:52of male sexual behavior? And the answer
29:55is yes.
29:57And how do you show it? With the most
29:58simple classic way of doing something in
30:01an endocrine study, which is get rid of
30:03the guy's testosterone. And you castrate
30:07the male, your rodent male, your
30:08non-human primate male, and what you see
30:11is there is a big drop
30:13in levels of sexual behavior. And this
30:16could range from male level lever
30:19pressing to get access to a female to
30:22courtship displays to extensive pomading
30:26of hair or something in the right
30:27neighborhood. And whatever the measure
30:29is, this is when normal testosterone
30:32levels are on board, and this is after
30:34castration, a very, very dramatic drop.
30:39Now, to fulfill the second, you know,
30:41ironclad requirement in endocrinology,
30:44the last thing you need to do now is,
30:46after the subtraction
30:49experiment, to do a replacement one.
30:52Artificially give back the normal levels
30:55to the castrated individual, and levels
30:57of sexual behavior go back to there.
30:59Whoa, okay, that proves that we have a
31:02causal relationship here.
31:05Not so fast.
31:06First thing to note, which is 0%
31:10testosterone and sexual behavior goes
31:12way, way down, it doesn't go to zero. In
31:15every species looked at, starting with
31:18the embarrassing sexual behavior of
31:20everyone's pet dogs when they were 6
31:21years old, even after being neutered,
31:24what you see is there's a level of
31:26residual sexual behavior. Rodents, dogs,
31:29primates, including humans. This is a
31:32critical point. How much residual sexual
31:36behavior is there after castration? The
31:39more sexual experience before
31:42castration, the more there is going to
31:44be retained afterward. In other words,
31:49on a certain, like, totally artificial
31:51level, this amount of sexual behavior is
31:54being driven by testosterone. This
31:56amount, which persists here, is being
31:58driven by social experience. It's got
32:01nothing to do with the hormones. Yes,
32:03this is ridiculous dichotomizing into
32:05this, but the fact that it doesn't go to
32:07zero, and the fact that the more sexual
32:09experience pre-castration, the more
32:12residual behavior, this is a vote for
32:14just how much of a role social
32:17experience, social conditioning plays.
32:21Next thing that takes away from the yes,
32:23it's all caused by testosterone. Now you
32:26do an elaboration on the study. You
32:28castrate a male,
32:30and now, instead of replacing with 100%
32:33of normal levels, you give 10% of normal
32:37levels, or you give 200% of normal
32:40levels. And what do you wind up seeing?
32:43If testosterone plays a strictly
32:45causative role, even in this range, you
32:48were going to get something This is
32:50going to be lower than 100% and this is
32:52going to be higher. That's not what you
32:54see.
32:56Instead, it is something like that.
32:59You get roughly the same reinstatement
33:01of sexual behavior with when you replace
33:05return testosterone levels over anything
33:08roughly approximating the normal
33:10physiological range. What does that tell
33:13you? The brain circuits we learned about
33:16the other day involved in sexual
33:18motivation, it requires testosterone
33:21around to work fully,
33:23not entirely, but to work fully, but
33:26those brain regions are not really all
33:29that concerned with the exact level of
33:31testosterone. Rough approximation of
33:35normal, rough approximation of normal,
33:37has the exact same effect. If you were
33:40seeing a tight relationship in a male
33:43between the amount of sexual behavior
33:45and testosterone levels, it's not
33:47because every little smidgen bit of more
33:50testosterone is going to drive more
33:52sexual behavior, it's because every
33:55little additional smidgen of behavior is
33:57going to drive higher testosterone
33:59levels.
34:00So, we've got this really important
34:02observation. Yes, testosterone is needed
34:05in species after species, including
34:07humans, for the normal range of sexual
34:10behavior. Just as importantly,
34:12castration never drops it down to zero,
34:15the more social experience, that whole
34:17song and dance. And very importantly, as
34:20well, the system is not sensitive to
34:23little differences in testosterone
34:25levels. Stating that a different way, if
34:28some guy has 1 and 1/2% more toss
34:32on board than the guy sitting next to
34:34him or or than he had last week, is that
34:37going to mean he is going to be more
34:38sexually motivated, more aroused? No,
34:41not at all. Within the normal range, the
34:44system doesn't distinguish it. The
34:46relevant brain regions are sensitive to
34:49testosterone and require it, but do not
34:51care a whole lot about the levels.
34:54One exception, which is if you instead
34:56of say 200% push testosterone levels
35:00like 1,000%,
35:02tenfold higher than normal, this is
35:04supra
35:06physiological, which means it's out of
35:08the normal range, which means nobody's
35:10normally generate those sorts of levels.
35:12Put it up in that range and you will get
35:15an increase in sexual behavior and
35:17sexual arousal. When do you see this?
35:20The idiots who go and abuse anabolic
35:23steroids for their weightlifting or
35:25whatever, people doing that are not
35:27pushing up their testosterone levels
35:29into the higher range of what human
35:32bodies gen can generate, they are
35:34pushing it way above the normal range.
35:37In that range, you
35:39do see an increase in sexual
35:41proceptivity.
35:43In a week or so, what we will see is the
35:46exact same story. It will be the exact
35:49same chart here when asking the
35:51question, "What does testosterone have
35:53to do with aggression?" And what you'll
35:55see is the exact same conclusions. What
35:58are we beginning to see here? That
36:00testosterone is not playing a strictly
36:03causative role. It is playing one of the
36:06words that should be becoming repetitive
36:08here and clearly really important,
36:11testosterone is playing a modulatory
36:14role.
36:15What testosterone does is sensitize you
36:18towards stimuli
36:21that are evocative of sexual arousal. It
36:24lowers the threshold.
36:26And that could be shown in all sorts of
36:29studies, but where it's most clear-cut
36:31is in this case. Does testosterone cause
36:35the sexual behavior? No, but when it is
36:37on board, it facilitates it, it
36:41modulates it. Theme again and again and
36:43again.
36:44And that obviously has tons to do with
36:47individual differences. One last hormone
36:49to mention in this realm of hormone
36:52levels over the last couple of weeks,
36:54months, seasons, or so, the hormone
36:56melatonin. And I think that's the only
36:58time melatonin is going to be mentioned
37:00in class. Melatonin has something to do
37:02with telling the body what time of year
37:05it is. It is responsive to the amount of
37:08light you are exposed to. What is
37:10melatonin about? It is one of the
37:12driving forces on seasonal mating. Those
37:15species where you suddenly get on one
37:18afternoon each year all the wildebeest
37:21ovulate the same afternoon kind of
37:22thing, it is almost certainly a whole
37:25pathway in the brain sensitive to the
37:28amount of light and the amount of light
37:30per day over recent weeks, which by way
37:32of melatonin triggers the onset of the
37:35mating season.
37:36Do humans have a seasonal mating
37:38pattern? There's a smidgen of evidence
37:41for it. If we've got it, it is a very
37:44very weak echo of what you see in some
37:46other species.
37:48Okay. Now we shift over to getting
37:52really way back then instead of over
37:54your last 28 days or over the last three
37:56seasons, now beginning to look at
37:58perinatal factors. Perinatal, before
38:02birth, prenatal, after birth, postnatal,
38:05very early development.
38:08First off, focusing on early
38:10environment. Environmental factors
38:13having something to do with adult sexual
38:15behavior. What we can translate that
38:17into is ways in which early environment
38:20affects every single one of these
38:21subsequent ones. What does early
38:23environment childhood have to do with
38:26shaping of sexual behavior? A theme
38:28that's also going to come out in every
38:31topic we're going to hear of after this.
38:34Buzzwords that should beginning to be
38:36keeping you awake at night, modulatory,
38:39contingent, if then, all that stuff.
38:41Here's another one. Here's another
38:43concept that comes through.
38:45The evidence shows that there is very
38:48little about early life experience which
38:52influences the quality, the way in which
38:56an organism goes about having sex.
38:59What's another way of stating it? This
39:01is a pretty set in stone bunch of fixed
39:03action patterns. Early experience is not
39:06about learning how to be sexual.
39:09Early experience is about learning the
39:11appropriate social contexts for being
39:15so. And that is shown in species after
39:18species. That is what experience is
39:20about. Not how to do it, but when to do
39:23it, and who you should not in your right
39:25mind try to do something proceptive to,
39:28and things of that sort. This is what
39:30early experience is about. And what
39:32we're going to see in a week is the
39:33exact same boring paragraph. Early
39:37experience does not teach organisms how
39:39to be aggressive. It teaches organisms
39:41the appropriate context for being
39:44aggressive.
39:45So, what's the sort of evidence for
39:47this, for these early effects? One
39:49example, whole literature that emerged
39:51that is covered somewhat in the zebra
39:53book in another domain, but this whole
39:55literature that emerged in the 1950s,
39:58work looking at captive primates, what
40:01are the consequences of growing up in a
40:04certain degree of social isolation? What
40:07happens to behavior, and eventually
40:09people studying behavior and physiology,
40:11what happens to behavior in adulthood if
40:14you are a young rhesus monkey who grows
40:18up only with peers and no mother
40:21or grows up only with a mother and no
40:23peers or grows up with mother being
40:25present only intermittently or at the
40:27most extremes growing up with neither
40:30mother nor peers or any other member of
40:32your species around. You will see in the
40:34book a whole discussion of the ethics of
40:36these studies, but what does your early
40:39social environment have to do with
40:41things like sexual behavior and what you
40:43see coming out the end is when you
40:45looked at these adult primates since
40:47replicated over and over they go about
40:50the sexual behavior the plain old way
40:52that everybody else does, but they do it
40:54in totally socially inappropriate
40:57context. And thus you have these males
41:00who were raised in some degree of
41:01isolation early on growing up and
41:03carrying out perfectly normal sexual
41:05fixed action patterns on the towel in
41:08the room on the bowl of food on the who
41:11knows what wrong context. You have
41:14trying to do things with animals you
41:16should not go anywhere near in terms of
41:18social dominance and such inappropriate
41:21context. Early experience shaping not
41:24how but when what the if then clauses
41:28are.
41:29More issues of early experience shaping
41:32adult sexual behavior arousal
41:34proceptivity etc. We already heard one
41:36example of this with humans. That's the
41:39whole kibbutz literature. That was that
41:41whole business that if you spend lots of
41:44intimate time with somebody before age
41:47six what you will do is in some
41:50subliminal imprinting way decide forever
41:53after this individual does not feel like
41:55a potential mate. This individual feels
41:57like a sibling. That was the example in
42:00the recognizing relative lecture of
42:02showing that hurray we are such a
42:04cognitively sophisticated species. We
42:07can figure out who's somebody's fourth
42:10cousin three steps removed is by
42:12thinking, and that's how we make our
42:14mating decisions. Showing instead in
42:17those studies, there is this
42:18non-conscious level. One of the rules
42:21that humans have is lots of exposure
42:24intimately to somebody early on in life,
42:25and you are not going to be very likely
42:28to get that prospective behavior stuff
42:30going on later, part of turning them
42:33into a pseudo kin because of that early
42:35exposure.
42:37One additional domain I will touch on
42:39here in terms of early experience, which
42:41is what does early experience have to do
42:43with sexual orientation?
42:45And depending on which decade you were
42:47asking this question, the answer would
42:49range from everything to virtually
42:52nothing.
42:53Going back to the virtually everything
42:57time, which was dominating sort of the
42:59first half of the 20th century, how
43:01people thought about the subject, what
43:03you had were two broad models for what
43:06sort of early environments increased the
43:09likelihood of boys becoming gay as
43:12adults. And these were the two models.
43:14The first one was the absence of a
43:17father figure model. And this was one
43:20straight out of monkeys learning who
43:22they should try to pelvic thrust with or
43:24some such thing. This was the argument
43:26that what do father figures provide
43:29appropriate training for appropriate
43:31contexts for prospective sexual
43:33behavior. Growing up absent a father
43:36father figure increasing the likelihood
43:39of being gay.
43:40The other model was having this totally
43:44pain in the neck neurotic screwed up
43:46mother who, as basically said between
43:48the lines, makes you crazy when you grow
43:51up, and thus you have circa 1950
43:54psychiatrically certifiable disorder of
43:58having a different sexual orientation.
44:00Obviously, where I'm going to head right
44:02now is there has not been a slightest
44:05shred of evidence over the years either
44:07for the missing father figure model of
44:10sexual orientation or the neurotic
44:12mothering style model, complete
44:15nonsense. Nonetheless, dominating
44:17thinking about what was going on there.
44:19Okay, so what we are now ready to shift
44:22to is what's going on with hormones
44:24around this time period. Let's take our
44:275-minute break and then we'll resume.
44:31Looking at what perinatal
44:33hormone levels have to do with adult
44:35sexual behavior. And you already know
44:38the answer. You know it in your hearts
44:40by now, which is, well, it depends on
44:42what species you're looking at. And what
44:45we will see is a very similar thing to
44:47the rule there, which is in lots of
44:49species, rodent species, prenatal or
44:53perinatal hormonal environment has
44:55everything to do with adult sexual
44:58behavior. And by the time we get to
45:00humans, what we'll see is maybe kind of
45:03sort of more research needed. What we
45:05begin with here, implicit in that, is a
45:08dichotomy that runs through all of
45:10endocrinology when thinking about
45:11behavior. The effects of hormones back
45:15when you were little, jargon in the
45:17field, an organizational
45:19effect of the hormone.
45:21And what that is about is explicitly is
45:24what are hormones doing at that time in
45:26terms of organizing what kind of brain
45:28you're developing there.
45:30Effects of hormones instead in this
45:32range or so, what you were talking about
45:35is an activational hormonal effect.
45:39So this is a very sort of consistent
45:40dichotomy that people in the business
45:42use. Early early hormonal environments
45:45having organizational effects on the
45:47nervous system, hormones forever after
45:50having activational effects. So what you
45:52see is in rodent species that perinatal
45:56hormone exposure has massive
45:58organizational effects that dramatically
46:01influence sexual behavior.
46:03What you also see is it's not so
46:06dramatic and clear-cut. A whole
46:08literature initially suggesting that,
46:11for example, male rodents, if they are
46:13not exposed to testosterone perinatally,
46:16will have a different male rodent sexual
46:19orientation later on. A dichotomous
46:21outcome what a huge literature now shows
46:24is something that is evident to every
46:27sort of human sexologist for centuries,
46:29which is it's not a dichotomous
46:32function. It is on a continuum in terms
46:35of sexual orientation, and 300 different
46:39species have been documented by now to
46:41have both heterosexual and homosexual
46:44behavior
46:46at different times in natural
46:47naturalistic settings. So, perinatal
46:51hormones having organizing effects on
46:53adult sexual orientation, what you see
46:56is these are not all-or-none properties
46:58at all.
47:00What else? Okay, what you see
47:02specifically in non-human primates is
47:06perinatal period, expose a female monkey
47:10fetus to high testosterone levels, and
47:13what you will do is masculinize
47:16the brain.
47:17Masculinize the brain having thus an
47:19organizational effect. What does
47:21masculinization then manifest itself as
47:25in adulthood? If nothing else is
47:27different, it has no effects at all.
47:30On the other hand, if you
47:33inject a female monkey who is
47:36masculinized perinatally, if you inject
47:39her with androgens, with testosterone,
47:41you get a wild burst of male fixed
47:44action patterns. In other words, you've
47:47got an if-then clause. If and only if
47:51there was prenatal masculinization,
47:54then testosterone will have an acute
47:57activational effect on sexual behavior.
48:02Okay, translating this. Okay.
48:06pre
48:15Okay, so in the absence in a normal
48:17female monkey, in the absence of
48:19prenatal androgens or adult androgen
48:21levels, this is the amount of male fixed
48:24action pattern of sexual behavior. Now,
48:26prenatal
48:28androgenization,
48:29normal low androgen levels in adulthood,
48:34same low levels. Now, no prenatal
48:37androgenization and exposure to
48:39androgens in adulthood, same low levels.
48:42Prenatal exposure and acute activational
48:45effects and suddenly you get high rates
48:47of male typical fixed action patterns.
48:50So, what we've got here is a contingent
48:54organizational effect. Yet again, one of
48:56our if-then clauses. This one not being
49:00a if this physiology is going on only in
49:03this social environment, then this is if
49:06this early life endocrine environment
49:09occurs coupled with this acute adult
49:11one, then Yeah, question.
49:13Is it that the regular females don't
49:15have receptors? They don't have as many
49:17receptors?
49:19That is a great question and as you're
49:21about to see, the answer is so insanely
49:24complicated you are going to regret
49:26having asked that question for days.
49:28But, you were going to find out about it
49:29anyway.
49:30Um apropos of that, I just forgot a
49:32great question during the break, which
49:34is okay, when you've got those uh
49:37weightlifter folks there abusing their
49:40steroids, their anabolic steroids, their
49:42testosterone drive drugs, when you push
49:44things up into the supra physiological
49:47range, higher than the body normally
49:49ever comes up with, do you see a
49:51phenomenon from last Wednesday? Does the
49:54body downregulate the number of
49:56testosterone receptors? And you see
49:59exactly the case, but you could never
50:01downregulate them low enough to
50:04compensate for the huge screaming
50:06testosterone signal. It is a partially
50:08successful compensatory response.
50:12Okay. What have you got in terms of
50:15humans in terms of perinatal
50:18androgenization of females? And people
50:20used to know exactly the answer to it.
50:23First off, when do you get human females
50:26as fetuses and it's predominantly in
50:28humans prenatal rather than postnatal
50:30effects. It depends on sort of how fast,
50:33how much of development occurs before
50:35birth. But in humans when are
50:37circumstances where female fetuses will
50:40get heavily androgenized, historically
50:42two circumstances.
50:44One is in the case of a disease where
50:47there is something wrong with the
50:49adrenal gland and they pump out tons of
50:51testosterone. You remember, if I
50:54actually did say this and if I didn't I
50:56hope you're not remembering it
50:57hallucinatory, but you'll remember that
51:00the adrenal glands make a certain amount
51:03of testosterone and in females it pumps
51:06out maybe 5% the levels that males do.
51:08When you have this disease of an
51:11overactive adrenal system, you pump out
51:14way too high of levels of testosterone.
51:16A disease called congenital adrenal
51:19hyperplasia.
51:21Hyperplasia the number of cells, hyper
51:25Okay, come up with a limerick about that
51:27one, I dare you. Is it possible to come
51:29up with a haiku? How many syllables are
51:31there in congenital adrenal hyperplasia?
51:33Well, depends if we're talking about
51:35rodents or not. So, congenital adrenal
51:37hyperplasia, a genetic and inborn error
51:40of metabolism in the adrenal glands and
51:43you pump out huge amounts of androgen.
51:45So, suddenly there is a world of the
51:47occasional girl who is born suffering
51:50from this disorder or the mother
51:53suffering from it during pregnancy who
51:55has been prenatally androgenized.
51:58The other population, thanks to a drug
52:00that was very popular in the 1950s, a
52:02drug that decreased the likelihood of
52:04miscarriage, that was very heavily used
52:07at points around then, drug called
52:09diethylstilbestrol,
52:10DES, and in a subset of women, their
52:14farm their biochemistry was such that a
52:16lot of the DES was converted to
52:19androgens. So, you had kids who were
52:22prenatally androgenized girls either
52:25because of this congenital adrenal
52:26hyperplasia or because of DES exposure.
52:30So, then the question immediately
52:31becomes, "Okay, so what are they like
52:34afterward?" And this prompted the great
52:37large massive set of studies on the CAH,
52:41the congenital adrenal hyperplasia, on
52:42the CAH girls as they grow up, and you
52:45knew exactly what the expectation was
52:47straight out of primates here, non-human
52:49primates, which was this was going to
52:51have masculinizing effects on their
52:54behavior.
52:55And what was shown was in adulthood,
52:58there were all sorts of differences. No,
53:00not just in adulthood, starting around
53:02adolescence, there were all sorts of
53:04differences in the behaviors of these
53:05girls. And as we'll see next week, a
53:08whole cluster of them were thought to
53:10fall into the realm of aggressive
53:12behavior, but what was seen here was
53:14eventually a higher likelihood of
53:17becoming a lesbian in terms of sexual
53:20orientation. Whoa, what we've just shown
53:22is prenatal androgens and you produce a
53:26lesbian later on, that's just There was
53:28a little problem with these studies, a
53:30slight confound, and one that's going to
53:32be very pertinent next week as well when
53:34talking about the aggression stuff, the
53:36confound being if you were prenatally
53:38androgenized, you would get born with
53:40kind of weirdo genitals, and you would
53:44have sort of intersexual genitals in all
53:46sorts of ways, and all of these girls
53:48typically had to have gone through a
53:51dozen rounds of reconstructive plastic
53:53surgery over the first decade of your
53:56life. These were not girls where the
53:58only thing different about them was what
54:00sort of hormones their brains were
54:01marinating in back when they were
54:03fetuses. These are girls who grow up
54:06with this really interesting part of the
54:08body that all sorts of people seem kind
54:10of creeped out about, but doctors are
54:12endlessly examining, and all sorts of
54:15painful surgeries, and this literature
54:17was completely confounded by the fact
54:19that there was all this masculinization
54:23of genitalia and a whole world of
54:26surgeries, often confusion about gender
54:29assignment early on in life. Things were
54:31not merely a change in the hormone
54:34levels.
54:35So, it remains relatively unclear.
54:38There's by now, at this point, weak
54:39evidence of prenatal androgenization
54:42increasing the likelihood of a woman
54:44being gay as an adult.
54:47I'm seeing here in my notes I have the
54:49words Indonesia, tomboy, and
54:51Hobson-Jobson.
54:53And I haven't a clue what that's about.
54:54So, we will just skip over that. Okay.
54:59What we begin to see here is another
55:02feature of early experience. What does
55:05Where are we? Prenatal endocrine
55:07environment have to do with sexual
55:10identification, which is different than
55:12who you were sexually attracted to, but
55:15rather what sex you feel yourself to be.
55:17And what we heard the other day with the
55:19transsexualism example is you could have
55:23gender being dictated by your
55:25chromosomes and which which organ which
55:29gonad types of gonads you have and
55:31hormones and all of that, but that is
55:33not enough to determine it. There are
55:35clearly other things that can happen
55:37that could produce a very, very
55:39different gender identity.
55:41What also was seen from that literature
55:44of individuals who were born intersexual
55:47where they have sexually ambiguous,
55:49gender ambiguous genitalia is it is far
55:52from clear which decision to make
55:56whether that was made circa 1950s by the
55:58surgeon with no consultation with the
56:00parents or fortunately these days a very
56:02different scenario in terms of how
56:05successful the assignment is by the
56:08individuals in the outside world, what's
56:10going on in terms of sexual identity
56:12inside.
56:13Now, what this begins to bring up is the
56:16most miserable, irritating, confusing
56:19thing about the effects of steroid
56:22hormones in the brain, which is where
56:24your question came from and this is
56:25where you're all going to start to
56:26regret this, but it actually is
56:29necessary in terms of an important
56:31point. Okay, so you got testosterone
56:33and what does testosterone do? We know
56:36already, it binds to testosterone
56:37receptors.
56:40Okay, the testosterone receptor and does
56:42its steroid hormone transcription factor
56:45deal.
56:46Throughout the 1970s, there was
56:48astonishing amount of confusing,
56:51irritated research done showing the two
56:54following things.
56:56In some parts of the body, testosterone
56:58has its effect as testosterone. It binds
57:02to the testosterone receptor. In some
57:04parts of the body, there is biochemical
57:07conversion of testosterone to something
57:10called dihydrotestosterone.
57:13Okay, it's not testosterone, it's a
57:14little bit different chemically. It
57:16binds to the same testosterone
57:17receptors, it works a different little
57:19bit differently. Okay, we can live with
57:21that. The thing that had people jumping
57:24off buildings was the discovery at the
57:26time that some of testosterone's actions
57:30are due to it being biochemically
57:32converted to estrogen,
57:35which then binds to estrogen receptors
57:37and causes male typical behaviors. Okay,
57:41it's at this point that about half the
57:43people in the field quit and went to
57:45business school because this was so
57:46confusing and impossible and all of
57:48that. This consumed years of labor of
57:52people trying to sort this one out. It
57:54goes as follows. Once testosterone
57:58enters a target cell, if this is the
58:01scenario that's going to happen, it's
58:02inside the cell that testosterone is
58:05turned turned to estrogen.
58:08In other words, this weirdo phenomenon
58:11has no effect on circulating
58:13testosterone levels. It's only in target
58:15cells that have the enzyme that could do
58:17that conversion. Okay, so it's an
58:20intracellular phenomenon. If this is
58:22leaving you totally in the dust, uh
58:25don't worry about it except for a small
58:26point coming in a while. Um but if you
58:28want to devote the rest of your life to
58:30figuring this out in more detail,
58:32there's something wrong with you. But
58:33what you've got here is normal
58:36circulating levels, but different
58:38effects throughout the body. In general,
58:40what is found is the effects of
58:42testosterone in the brain involve this
58:46turning it into estrogen,
58:48as symbolized meaninglessly by that
58:50asterisk. Throughout the secondary
58:53throughout the genitals or throughout
58:55the body and secondary sexual areas of
58:58skin and such, testosterone exerts its
59:01effects by being turned into
59:02dihydrotestosterone.
59:04And whatever parts are left over at that
59:06point, testosterone just does its
59:08regular old thing. Okay, so this is
59:10incredibly confusing how this can be.
59:13Immediately, or not so immediately, two
59:16things should come to mind. Okay, so
59:18prenatal
59:21testosterone levels are going about
59:22their normal prenatal organizational
59:25masculinization effects, and part of it
59:28is on how the brain organizes. So, what
59:31we just saw was prenatal neurobiological
59:35masculinization requires testosterone to
59:38be working like estrogen in the brain.
59:42Okay.
59:43Why don't all the female fetuses then
59:45get androgenized?
59:47Since they're not generating estrogen
59:49right on site, they're within the cell,
59:51but they're getting estrogen through
59:53some other route as their fetal ovaries
59:55start to work. Why isn't mom and her
59:58estrogen androgenizing every single
1:00:00fetus out there? How is it possible to
1:00:03ever get a female?
1:00:04And the answer to that is there is a
1:00:07protein
1:00:09which occurs during pregnancy that
1:00:11occurs in the circulation.
1:00:14And what it does is it binds estrogen.
1:00:18And it takes it out of action. It leads
1:00:20to estrogen being degraded.
1:00:22In other words, estrogen in the
1:00:25bloodstream of a fetus
1:00:27never has an effect on any cells in the
1:00:29body.
1:00:30Estrogen, whether derived from the
1:00:32female fetus beginning to get her own
1:00:34ovaries going there, or from mom's
1:00:37circulation, the estrogen has no effect.
1:00:40In other words, the only fetuses that
1:00:42ever have estrogen inside their neurons
1:00:45are fetuses that are male where the
1:00:48estrogen came from testosterone.
1:00:51So, you have to have this protein, and
1:00:53it's something called alpha-fetoprotein.
1:00:56It only occurs in fetal life. This winds
1:00:58up being the solution. What is implicit
1:01:00in that? You do not get the organizing
1:01:03organizational feminizing effects of
1:01:06hormones prenatally because of estrogen.
1:01:10Because you've just guaranteed that
1:01:11doesn't happen. You're getting
1:01:12androgenizing effects that way. You
1:01:14don't get prenatal feminizing effects
1:01:17from estrogen. Where does the brain
1:01:19feminization come from? The irritating
1:01:21answer back when was this was always uh
1:01:25uh sort of the same phrase was always
1:01:26used that the female brain is a default
1:01:29brain.
1:01:30You have to actively actively in a
1:01:33muscular excited
1:01:35you know, chopping down the trees and
1:01:37clearing the prairie sort of way. You
1:01:39have to actively do something hormonal
1:01:41to masculinize a brain and in the
1:01:43absence of that you just kind of wind up
1:01:45with one of them female brains. What's
1:01:48clear now is this default model was not
1:01:50really the case. It's other hormones
1:01:52that are doing that there. Okay, so this
1:01:54totally confusing irritating thing that
1:01:57everybody had to assimilate at the time
1:01:59of testosterone having different effects
1:02:02having been converted to different
1:02:04messengers in different parts of the
1:02:06body and that having to produce this
1:02:09whole complex,
1:02:11you know, Rube Goldberg sort of solution
1:02:13as to how to ever get a female.
1:02:15Now one additional interesting
1:02:17implication.
1:02:19Back to you remember the other week?
1:02:21Remember
1:02:22actually did I talk about it or was it 2
1:02:24years ago or
1:02:27Jesus. Okay, I think I mentioned
1:02:29testicular feminized males.
1:02:32Yes, good. Okay, thank you for the
1:02:33grounding. Um testicular you remember
1:02:36what those folks were about? This was
1:02:37someone who was phenotypically a girl
1:02:40and would not hit puberty, would not
1:02:43start menstruating until
1:02:46every other kid in her grade had and it
1:02:49still hasn't happened still hasn't
1:02:50happened and you take her to the doctor
1:02:52and what is discovered is that she is
1:02:54not female. She is a testicular
1:02:56feminized male and we went through
1:02:58exactly what the building blocks were of
1:03:00that. The individual is chromosomally
1:03:03male, has testes, undescended testes, is
1:03:06producing tons and tons of testosterone.
1:03:08What was the problem there? We know
1:03:11already it was the mutation in the
1:03:13testosterone receptor.
1:03:15So if testosterone is not able to send a
1:03:19signal through the testosterone
1:03:20receptor, you don't get a male
1:03:23phenotype.
1:03:25And you get an individual whose sexual
1:03:28identity is female, because these are
1:03:30people who are girls and grow up to
1:03:33become women, women who simply can't
1:03:35reproduce, but otherwise the sexual
1:03:37identification is female.
1:03:41This should be really puzzling now, cuz
1:03:43what we've just seen is if you have this
1:03:46mutation in the testosterone receptor,
1:03:48you're not going to get any
1:03:50signaling mediated by testosterone.
1:03:54You're not going to get any signaling
1:03:56mediated by dihydrotestosterone,
1:03:59but you're going to get perfectly normal
1:04:01masculinization of the brain by way of
1:04:04estrogen. In other words, people who are
1:04:07testicular feminized males, who in terms
1:04:10of their sex identification have been
1:04:12female from day one and will be for
1:04:14their entire lives, nonetheless
1:04:17prenatally they had masculinization
1:04:20organizational effects on that brain.
1:04:22What does that tell you? All of this
1:04:24great hormone stuff in some cases
1:04:27doesn't hold a candle to social sex
1:04:30identity assignment, which is when you
1:04:33have somebody growing up with a certain
1:04:36gender's genitals and all of you treat
1:04:39that individual as a girl, it turns out
1:04:42virtually 100% of the time it doesn't
1:04:44matter that you still had this pathway
1:04:47working prenatally, all the social
1:04:49queuing produces a female sexual
1:04:52identity.
1:04:53So, we've just gotten a big, big vote
1:04:55here for this is doing all sorts of
1:04:58exciting endocrine stuff there, which
1:05:00nonetheless may not hold a candle to
1:05:03some social environmental factors at
1:05:05this end.
1:05:06Okay, what else do we have here?
1:05:11Something I don't want to talk about.
1:05:12Okay, so hurling on. Now we are ready to
1:05:16move back another box here, which is
1:05:19genetics. What does the genetic makeup
1:05:22of an individual, not of a population or
1:05:24species, what do genes have to do with
1:05:27sexual behavior?
1:05:29And the answer is lots of things,
1:05:31starting with the fact that genes
1:05:33determine which gonads you make as a
1:05:36fetus.
1:05:37And thus that determines which sex
1:05:40hormones you were secreting, and thus
1:05:42that determines what sort of genitals
1:05:44you wind up with and secondary sexual
1:05:46stuff, and off you go running with that.
1:05:49And we've seen that nonetheless that can
1:05:51be blunted by depending on the
1:05:53environment, the testicular feminized
1:05:56male pathway here showing that. Okay, so
1:05:58genes play a role in terms of just sheer
1:06:01sex determination.
1:06:04What is known about genes and sexual
1:06:07orientation?
1:06:08This has been studied a lot because this
1:06:10is one of those irresistible subjects
1:06:13that ooh, people just can't get enough
1:06:14of. What's up with that? What does the
1:06:16literature show? A certain degree of
1:06:19heritability of sexual orientation. And
1:06:22you should be able to leap up right now
1:06:24and say exactly what that means and
1:06:25doesn't mean. Here's the sort of
1:06:27evidence. Twin studies.
1:06:30Twin studies. When you look at
1:06:31monozygotic twins, identical twins,
1:06:34there's approximately 50% concordance of
1:06:38sexual orientation.
1:06:41Translated into the terms that people
1:06:43are usually focusing on in those
1:06:44studies, which is to say if somebody is
1:06:47gay, their identical twin has a 50%
1:06:49chance of being gay.
1:06:51Dizygotic twins, non-identical twins,
1:06:55what is the number? Instead it's 22%
1:06:58covariance.
1:07:00What's the number with other siblings?
1:07:029% covariance. So what do we see here?
1:07:06We see a suggestion that the more genes
1:07:08you have in common with somebody, but
1:07:10also the more prenatal environment you
1:07:13had with your non-identical twin, all of
1:07:15that stuff, the greater the likelihood
1:07:17of sharing a trait of sexual
1:07:18orientation. And you can be off and
1:07:20running right now about the limitations
1:07:23of that interpretation.
1:07:25Because obviously this suggests genetic
1:07:28effects, and it also suggests the whole
1:07:30world of identical twins being treated
1:07:33differently than non-identical ones.
1:07:36One additional piece in that story,
1:07:38and this was another one of those
1:07:40front-page stories in Time, Newsweek,
1:07:42etc. And this came a couple of years
1:07:45after Simon LeVay's finding of that
1:07:47sexually dimorphic nucleus in the brain,
1:07:49that whole deal there. And this was the
1:07:52reporting of the first genetic markers
1:07:54for sexual orientation.
1:07:57And this was reported by a geneticist at
1:07:59National Institutes of Health, a guy
1:08:01named Dean Hamer, who was a very
1:08:03well-respected geneticist. And what he
1:08:06reported was that he was finding genetic
1:08:09markers for sexual orientation. In other
1:08:13words, certain gene locations that were
1:08:16more likely to be shared between gay
1:08:20siblings where both were gay than
1:08:22between
1:08:23partially gay siblings or non-gay
1:08:26siblings or however that one runs. You
1:08:29you know that one by now. Beginning to
1:08:31find genetic markers going with this.
1:08:33This was really interesting, and no
1:08:36surprise what the newspapers were
1:08:38screaming about within days was
1:08:39scientists announced today they have
1:08:41discovered the gay gene.
1:08:45Okay, great. Maybe we shouldn't let
1:08:47people learn any science out there. All
1:08:49right, so scientists have discovered the
1:08:51gay gene.
1:08:53Goes all the newspapers and Reader's
1:08:55Digest, and if I recall at the time
1:08:57Ronald Reagan as well, but he was
1:08:59completely demented at that point, so I
1:09:01won't hold it against him, but the
1:09:02people at Newsweek should have known
1:09:04better. So, we have cover stories about
1:09:06the gay gene. Obviously, you can rip
1:09:09this to shreds right now. Number one,
1:09:11this was not a gene, this was a genetic
1:09:14marker. You remember the other week the
1:09:16difference there.
1:09:18Number two,
1:09:19there was no consistency in this. What
1:09:23do I mean by this? This pair of
1:09:26identical twins
1:09:28would tend to share a certain genetic
1:09:30marker
1:09:31which was predictive of sexual
1:09:33orientation, and the next pair over, it
1:09:36wasn't the same area of genes that
1:09:39showed that covariance, it would be a
1:09:41completely different area that they had
1:09:43in common. And another pair, a
1:09:45completely different area. You got this
1:09:47genetic covariance
1:09:50in various twin pairs, but it wasn't the
1:09:52same gene marker in all those cases. All
1:09:55of them were different, which makes zero
1:09:58sense in terms of the genetics. The
1:10:00biggest problem with it is that since
1:10:02then all sorts of people have tried to
1:10:04replicate the finding, and it has never
1:10:05been replicated. Nonetheless, Hammer
1:10:08became quite famous for this. Um he is
1:10:10gay, and he used this sort of
1:10:12politically some of the same ways that
1:10:13Simon LeVay did with his study, which is
1:10:16don't tell me about choice, don't tell
1:10:18me about my neurotic mother anymore. We
1:10:21are looking at a very hardwired
1:10:23biological trait, what sexual
1:10:25orientation you have. LeVay's finding I
1:10:28have found quite convincing in terms of
1:10:29replications. Hammer's, nobody else has
1:10:32replicated it, and the actual genetics
1:10:34that he reported makes no sense at all.
1:10:37So, great limitations in what you can
1:10:40make of this.
1:10:41Okay, this allows us to make our great
1:10:44final leap to the left with this thing,
1:10:46this logic that's going to run through
1:10:48everything we talk about, which is the
1:10:50second you're talking about genes, you
1:10:52are implicitly talking about the
1:10:56evolutionary history that brought about
1:10:58the existence of those genes and that
1:11:00you're also talking about the proteins
1:11:03made by those genes and early
1:11:05environment changing the epigenetic
1:11:07state of transcribing those genes. Yes,
1:11:10yes, that whole song and dance now. So,
1:11:12now we have to transition to what does
1:11:15evolutionary biology tell us about
1:11:17sexual behavior?
1:11:19So, the first thing that it tells us is
1:11:21absolutely obvious, which is uh
1:11:23organisms have sex for the good of the
1:11:24species.
1:11:26Okay, so that one's out of the way. So,
1:11:28now we go to what is much more logically
1:11:31in terms of contemporary evolutionary
1:11:33thinking, contemporary starting circa
1:11:341965 or so, the whole notion of
1:11:37maximizing the number of copies of your
1:11:39own genes, all of that translated into
1:11:42sort of the economic terms of handing on
1:11:44copies of genes. What that basically
1:11:46states is sexual behavior is about
1:11:49reproduction.
1:11:51And people who would study phenomena
1:11:54like these in various rodent species or
1:11:57wildebeest ovulating the same afternoon,
1:11:59all of that, would say, "Yes, indeed,
1:12:03you only have sexual behavior when it's
1:12:05around the time when females are
1:12:07ovulating and yes,
1:12:10reproductive behavior is about
1:12:12reproduction. It's about passing on
1:12:13copies of genes."
1:12:15What soon began to fall apart was not
1:12:17only making sense of us with our having
1:12:20non-reproductive sex all sorts of times
1:12:23was the discovery that we're not the
1:12:24only species that does that. And far and
1:12:27away the flagship species as the sort of
1:12:31emblem of that are bonobo chimps,
1:12:34who are, according to almost all
1:12:36primatologists out there, the coolest
1:12:38primate species there is. Okay, bonobo
1:12:41chimps, they were historically known as
1:12:43pygmy chimps, uh which is to say that
1:12:46when people first discovered them in
1:12:48terms of scientists, they were viewed
1:12:49as, "Well, these are chimps, but they're
1:12:51just kind of weirdo atrophied chimps,
1:12:54which I don't quite know how you come up
1:12:55with a pygmy atrophied chimp, but that
1:12:57was the view. And not very interesting
1:12:59and what eventually became clear is they
1:13:01are a separate species of chimp.
1:13:03And bonobo chimps are utterly different
1:13:06from your standard issue Jane Goodall
1:13:09chimps. The game Jane Goodall chimps we
1:13:12have a tournament species with extreme
1:13:15high levels of male aggression, as we
1:13:17will hear about next week. You have
1:13:19chimps who are building weapons. You
1:13:21have chimps that form something
1:13:23resembling organized warfare. And
1:13:25meanwhile, over as it turned out on the
1:13:28other side of the Congo, which is where
1:13:30the main division occurs, you only find
1:13:32bonobos in one area of the Congo basin
1:13:35and they clearly have been
1:13:36reproductively isolated from all the
1:13:38rest of the chimps heading there east
1:13:40all the way to the Indian Ocean by way
1:13:42of the Congo. There, go on the other
1:13:44side of the river, you got the bonobos.
1:13:47And bonobos are totally different.
1:13:50Bonobos, unlike chimps, have virtually
1:13:53no sexual dimorphism.
1:13:56So, you're off and running with that
1:13:57one. We know exactly what that means.
1:14:00Bonobo chimps have female dominance
1:14:03rather than male.
1:14:05All bonobo chimps play the guitar and
1:14:08sing soulfully.
1:14:12What else? And we have astonishing
1:14:14amounts of sex.
1:14:16Wait a second, we just went off the
1:14:18rails here. A species with low degrees
1:14:21of aggression cuz they have virtually no
1:14:22aggression whatsoever. Species with low
1:14:24degree of aggression and with no sexual
1:14:27dimorphism in body size, what we're
1:14:29looking at is a pair bonding species, a
1:14:31monogamous species.
1:14:32Bonobos are not monogamous species.
1:14:36Bonobos make
1:14:38I don't know who look like a pair
1:14:40bonding species in comparison. Bonobos
1:14:42are the most sexually promiscuous
1:14:44species on Earth. Bonobos have
1:14:47astonishing amounts of sex with every
1:14:49other type of bonobo they could run
1:14:51into. They have sex in order to
1:14:53reproduce. They have sex in order to
1:14:56decrease tensions. They have sex in
1:14:58order to celebrate having decreased
1:14:59tensions. They have sex because it's an
1:15:01even number day of the month because
1:15:03it's an odd every variety and the vast
1:15:06majority of it being non-reproductive,
1:15:09non-reproductive because it's not at a
1:15:12time when anybody's ovulating or because
1:15:14it's with someone of the same sex or it
1:15:16involves sexual behavior which
1:15:18traditionally does not result in eggs
1:15:19getting fertilized and all sorts of
1:15:21variants that people will only dream
1:15:23about from buying books and trying to
1:15:25get lessons this sort of thing. And you
1:15:27have perhaps having something to do with
1:15:29that astonishingly limber spinal
1:15:31columns. But what you've got is a
1:15:33totally different picture. Wait a
1:15:35second. They're very low aggression
1:15:37and they have no sexual dimorphism, but
1:15:40they're as far from pair bonding as you
1:15:42can get and instead you have a highly
1:15:44promiscuous social system,
1:15:46female-dominated and they're all just so
1:15:48cool and wonderful you can't believe it.
1:15:50And every time people go to primatology
1:15:52meetings, if you study some dumb old
1:15:54stupid species like a baboon, you spend
1:15:57the whole time basically feeling like
1:15:58you're some sort of immature jerk
1:16:00because you're not hanging out with
1:16:01bonobos. They are the kings of
1:16:04primatologists these days, the people
1:16:05who study bonobos. As the sound bite
1:16:07goes, chimpanzees are from Mars, bonobos
1:16:11are from Venus.
1:16:13Okay. So, that's what the t-shirts say
1:16:15from the bonobo people at the
1:16:17conferences there. Totally different
1:16:19system. So, what we already see is
1:16:21violating our simple rules of what
1:16:23predicts a tournament species and what
1:16:25predicts a pair bonding one. What's most
1:16:27striking here is yes, reproductive
1:16:30behavior is for reproduction, for
1:16:31passing on copies of the genes, not for
1:16:33the good of the species, but we know
1:16:34individual selection can still and
1:16:36here's these guys having sex with 14
1:16:38other bonobos while they're all upside
1:16:40down or who knows what and it's not just
1:16:44for passing on numbers of copies of
1:16:45genes.
1:16:46Huge, huge exception there. And huge
1:16:49exception in lots of other species. And
1:16:52the ecologist Joan Roughgarden here in
1:16:54the biology department has made an
1:16:56argument there is far more
1:16:58non-reproductive sex that goes on in
1:17:00lots of different species, weakening the
1:17:02classic Darwinian concept from 3-4 weeks
1:17:05ago of sexual selection being a very
1:17:08important driving force. What sex is
1:17:11very heavily about is one gender
1:17:12choosing who they're going to mate with
1:17:14the other one, and it's all driven by
1:17:15that. I've seen instead if the world of
1:17:18bonobos, there's not a whole lot of
1:17:20evolutionary drive being built around
1:17:23sex equals reproduction. So, bonobos are
1:17:26really interesting. What's the sex
1:17:28they're about? One of the common themes
1:17:31that comes through is it's about
1:17:32promoting group cohesion.
1:17:35And one of the things that people
1:17:36emphasize or focus on with bonobos is
1:17:39you look at all sorts of other primate
1:17:41species, and what do they do when
1:17:43they're upset about something? They
1:17:44groom each other. What do they do when
1:17:46they're happy? They groom. What do they
1:17:48do? Social grooming as as termed the
1:17:50social glue, the social lubricant of
1:17:53society. You get a troop of baboons that
1:17:55have just gotten a bad scare from a
1:17:57lion, and as soon as the coast is clear,
1:17:59everybody comes down and spends the next
1:18:0130 minutes grooming each other. And
1:18:03sexual behavior in bonobos appears to be
1:18:07serving a very similar role. All about
1:18:09social cohesion, as well as decreasing
1:18:12individual tensions, reconciliation,
1:18:15things of that sort.
1:18:17Now, this flies in the face of a
1:18:19dominant theory that was around in the
1:18:21last century, the first part of it. And
1:18:23this was due to one of the grand poobahs
1:18:25in this field, a guy, this Brit named
1:18:28Solly Zuckerman. Solly Zuckerman, who
1:18:30eventually became Sir Solly Zuckerman,
1:18:33which probably didn't help him in
1:18:34society at all still despite that. But,
1:18:36old Zuckerman there was, for his time,
1:18:39the embarrassed Wynn Edwards. He was the
1:18:42Lamarck of the earliest part of the 20th
1:18:44century. The people who will only be
1:18:46remembered for coming up with
1:18:48Lamarckianism, old Lamarck, or coming up
1:18:50with something as idiotic as group
1:18:51selection. What Zuckerman came up with
1:18:54was the notion that sexual behavior is
1:18:57purely for promoting group cohesion
1:19:00and for decreasing violence. And all you
1:19:03need to do is go to half the movies out
1:19:05there or study half the species on
1:19:07Earth, and what you will see is sexual
1:19:09behavior or inability of or unrequited
1:19:13or whatever vanquished is the cause of
1:19:16the majority of aggression in organisms
1:19:19out there and various mammals, and that
1:19:22argues very strongly against it. So,
1:19:24what do you see in most species that
1:19:27have been studied, it's a strong
1:19:28argument against the Zuckerman stance.
1:19:31Nonetheless, you see in some species
1:19:33like bonobos and rough gardens argument,
1:19:36lots more species than people
1:19:37traditionally would think, where instead
1:19:39you see sexual behavior often serving a
1:19:42non-reproductive group cohesion sort of
1:19:46role.
1:19:47Okay, what else does evolution have to
1:19:49tell us about sexual behavior?
1:19:51One critical issue, and one that was
1:19:53touched on the first couple of lectures,
1:19:55is what does it cost you to reproduce?
1:19:58And there we get the hugely important
1:20:01asymmetry, which is sperm don't cost a
1:20:04whole lot, whereas eggs and pregnancy
1:20:07and postnatal care and all of that is
1:20:10hugely expensive. What is that the
1:20:12driving force on, according to all the
1:20:15sociobiological thinking, the fact that
1:20:17in species after species after species,
1:20:19females are more selective about who
1:20:21they will mate with than males. And as
1:20:24usually the case, the males are not
1:20:26selective in the slightest, and what you
1:20:28got instead is just a couple of a that
1:20:30it cost you, and that's not a big deal.
1:20:32Increased female selectivity, higher
1:20:35levels of it than males, are human being
1:20:37that it is all about the differential
1:20:39costs of pregnancy.
1:20:42What we also saw was not of pregnancy,
1:20:45but of reproduction and raising of kids.
1:20:47What we saw was the interesting realm
1:20:49where you got the exception to that,
1:20:51which were the pair-bonding species. The
1:20:53marmosets, for example, and what we saw
1:20:56back when was the male does as much
1:20:59child care as the female does, and the
1:21:01females always twin.
1:21:03So, around the time that the kids are
1:21:05born, the female has put in far more of
1:21:07the investment. She's gone through the
1:21:09pregnancy in terms of caloric
1:21:11expenditure. The males do, if anything,
1:21:13more of the child rearing in terms of
1:21:16carrying the kid around when foraging,
1:21:18all sorts of costly stuff like that. And
1:21:20eventually, what you see is the curves
1:21:26don't do that. But at some point, the
1:21:28cumulative amount of calories that the
1:21:30male has expended is greater than the
1:21:32female. That's when you see that
1:21:34cuckoldry business. That's where females
1:21:37will potentially pick up an abandon, and
1:21:40because the male has made the greater
1:21:42investment at that point, that is seen
1:21:43very frequently in bird species with
1:21:46pair-bonding. So, we've got here an
1:21:48exception to the argument that the cost
1:21:50of reproduction and child raising is
1:21:53always greater for females, and thus
1:21:54will always produce greater female
1:21:56pickiness for mates than you find in
1:21:59males. Nonetheless, you see that an
1:22:01awful lot.
1:22:03What else do you see? A whole world not
1:22:06only of female pickiness, but a whole
1:22:08world of male attempts to control female
1:22:11reproductive behavior. And this found in
1:22:13species after species after species, an
1:22:16obvious interpretation there in terms of
1:22:18male-male competition, decreasing the
1:22:21ability of females to mate with someone
1:22:23else. And that ranges from primates who
1:22:27are in consortships where the male will
1:22:30do what is often termed mate guarding,
1:22:32which is he tries to keep the female
1:22:34from going near any other guy, to all
1:22:36sorts of other stuff as well. And you
1:22:39certainly see this in the human realm.
1:22:41What are two cultural inventions humans
1:22:43have come up with to decrease the
1:22:45likelihood on by men to decrease the
1:22:49likelihood of women being sexually
1:22:51active outside that relationship. The
1:22:53first one is clitoridectomies and
1:22:56something else that serves a very
1:22:57similar function, which is inventions of
1:22:59things like chastity belts.
1:23:02What's up with that? What you find are
1:23:04cultural inventions like those in groups
1:23:08that tend to have occupations where
1:23:09males disappear for long periods. For
1:23:12example, nomadic pastoralists where
1:23:15depending on the time of year, you pick
1:23:17up with your camels or your cows or
1:23:19whatever, and you the guy are going to
1:23:21spend the next 3 weeks at the grazing
1:23:23area that's good 5 miles rest of there.
1:23:25And what this is about, the argument
1:23:28culturally for the clitoridectomies is
1:23:30it decreases female pleasure, decreases
1:23:33the likelihood of her having sex with
1:23:35someone else when you were elsewhere.
1:23:37What were chastity belts about when the
1:23:39guy picked up and decided to spend the
1:23:41next 6 years trying to liberate
1:23:43Jerusalem from the the Ottomans or
1:23:45whatever off on the Crusades. And just
1:23:48so you don't have any ideas over the
1:23:50next half decade while I go die from the
1:23:52plague somewhere in Eastern Europe,
1:23:54that's when those were again a model of
1:23:57cultures where there are extended
1:23:59periods of men being away from women,
1:24:02you have very often elaborate cultural
1:24:05inventions for men trying to control the
1:24:07reproductive access of women.
1:24:10What that also winds up doing is
1:24:12explaining what was thought to be the
1:24:14dominant models of reproductive success
1:24:17and reproductive choice in all sorts of
1:24:19other species. And seen for example in
1:24:21something like
1:24:23what you had was termed the linear
1:24:25access model of reproduction. It goes as
1:24:28follows.
1:24:29You have a social group, for example, a
1:24:31baboon social group, and there is only
1:24:33one female who is in estrus, only one
1:24:36female who is ovulating. Who winds up
1:24:39mating with her? The alpha male in the
1:24:41troop.
1:24:42Now instead, there's two females who are
1:24:45ovulating. Who gets the two females?
1:24:47Numbers one and two in the hierarchy.
1:24:49Three females, numbers one, two, and
1:24:51three get the female. And implicit in
1:24:54that is the activeness implied in the
1:24:56word get, the passive lack of choice at
1:24:59the female end of things. This was the
1:25:00linear access model in which male
1:25:03dominance rank was entirely predictive
1:25:05of male reproductive success.
1:25:07So, that's what people thought lots
1:25:09about then. That was the original
1:25:11thinking about the relationship between
1:25:13male dominance rank and reproductive
1:25:15success. As we will see shortly, it's
1:25:17not quite so clear.
1:25:20Lots of other species, where you see
1:25:22males attempting, in the evolutionary
1:25:24sense, attempting to limit female access
1:25:27to other males. This is the whole world
1:25:29of copulatory plugs. Lots of dog
1:25:33canine-related species, where a semen
1:25:36plug is left there in the vagina of the
1:25:38female, which soon hardens into a plug,
1:25:41and like nothing else is happening
1:25:44there. You see that. There are other
1:25:47cases. There are fly species where the
1:25:49male's penis is barbed, and
1:25:54Ooh, I heard a
1:25:56I'm not drawing that.
1:25:59What are you thinking?
1:26:01Where it's barbed, and where the barbs
1:26:02in fact go in the opposite direction,
1:26:06point back at the male. What's that? You
1:26:08get the penis in there, and it's not
1:26:10coming out again. It's like one of
1:26:12those, you know, those you put your
1:26:14fingers.
1:26:16Okay.
1:26:17Well, it's actually not like one of
1:26:19those, but you get the point. And what's
1:26:21that about? The male leaves his penis in
1:26:24there, which he manages to do without
1:26:26afterward because they can make new
1:26:28ones. And this is a very different world
1:26:30you've got here. Then you've got the
1:26:32whole world we've already heard about
1:26:34about sperm competition of sperm from
1:26:37one male in various fly species
1:26:39containing toxins that will kill the
1:26:41sperm of another male. Then there's a
1:26:44whole interesting world that goes on,
1:26:46which is when males mate mate with a
1:26:49female, they do something biochemically
1:26:52which decreases the sexual
1:26:54attractiveness of the female subsequent
1:26:56to that. In a number of fly species,
1:26:59males with mating release a chemical
1:27:01which decreases mating pheromone
1:27:03production in the female. And suddenly,
1:27:06nobody else is interested in her. Or
1:27:09there are other fly species where males
1:27:11release a chemical which decreases
1:27:13sexual proceptivity in the female.
1:27:16Viciously clever ways for males to
1:27:19control female repro- reproductive
1:27:20behavior after they've left, male-male
1:27:23competitive strategies.
1:27:25So, what do you see at the female end of
1:27:27things? No surprise, you see female
1:27:29counter strategies. One brilliant one
1:27:32that evolved in humans is this
1:27:34relatively unique human phenomenon of
1:27:37hidden ovulation.
1:27:39Yes, all that pheromone stuff and
1:27:41smelling people's armpits and things
1:27:43that don't happen much in the real
1:27:44world, but what you see for the most
1:27:46part is that humans are not terribly
1:27:48aware of where somebody is in their
1:27:50cycle. Humans have invented hidden
1:27:53ovulation. What's that meant to do?
1:27:56Decrease paternity certainty.
1:27:59And one argument is is that's a good
1:28:01mechanism for decreasing the likelihood
1:28:03of competitive infanticide. The other is
1:28:06it decreases male attempt to control
1:28:08female sexual behavior because it's less
1:28:11clear when you need to be doing that.
1:28:13So, counter strategies, more examples.
1:28:16This isn't argued that in some species
1:28:19that have non-reproductive sex
1:28:20throughout the cycle, that is a female
1:28:22counter strategy to again fool the male
1:28:25when ovulation is actually occurring,
1:28:28increasing the likelihood of that at
1:28:29such time she can get somebody else's
1:28:31genes. Other strategies, we've already
1:28:34heard about one, whack in the
1:28:36competitive infanticide one, which is
1:28:38that whole world of females that can
1:28:40fake being in estrus, that go through
1:28:43pseudo estrus. All of this meant to be
1:28:46ways of keeping males a little bit less
1:28:48certain of when they should be trying to
1:28:50control female sexual access, and thus
1:28:54she has more choice in the matter.
1:28:56What that brings us to is thus
1:29:00Oh, that's something interesting that I
1:29:02left out.
1:29:05Ah, it's not that interesting. Okay.
1:29:08So, back to male-male competition. This
1:29:11was first looking at male in lots of
1:29:13species, male attempts to regulate
1:29:15female sexual behavior, female counter
1:29:17strategies. What's up with male-male
1:29:19competition in terms of evolution and
1:29:21sexual behavior. Most obvious one being
1:29:24is male-male competition for
1:29:26reproductive access, and the standard
1:29:28old models being that linear access
1:29:30model, one female winds up with the
1:29:31number one male, two, and so on.
1:29:34What that thus begins to explain is when
1:29:36you look at all social species out
1:29:39there, the leading cause of aggression
1:29:41is male-male aggression built around
1:29:43female access. And as we'll see by next
1:29:45week, that is the case as well for every
1:29:47human culture ever looked at. You also
1:29:50see, of course, the sperm competition.
1:29:53And once again, we have one of those
1:29:54issues with humans, which is where do we
1:29:57fit on the spectrum there? If you have
1:30:00monogamous species,
1:30:02males tend to produce only small amounts
1:30:04of sperm, and tend to have small testes.
1:30:07When you have polygamous species, males
1:30:10want to pump out insane amounts of sperm
1:30:12to increase the likelihood of
1:30:14outcompeting some other guy's sperm if
1:30:16it shows up on the scene. Or for making
1:30:18a sperm plug, and what you wind up
1:30:21getting there in those species are large
1:30:23testes. So you look at the various
1:30:25primates, and chimps have gigantic
1:30:27testicles per body size. Gorillas do
1:30:30not. Gorillas that have a very different
1:30:32world of male-male com- What about
1:30:34humans? Once again, the same exact
1:30:36thing. We are about halfway in between.
1:30:39When compared to other primates, we are
1:30:41intermediate between a tournament
1:30:43species and a pair-bonding species in
1:30:45yet another domain. We've been hearing
1:30:47about this again and again.
1:30:50Something really interesting that has
1:30:52been shown in humans, which is
1:30:55No, I'm not going to tell that. That's
1:30:56too hard to explain. But it was great.
1:30:59You would really wish So now, what we
1:31:01have is also looking at evolutionary
1:31:04aspects of female choice in there. And
1:31:07in which cases do you get female-female
1:31:10competition?
1:31:11First off, the answer was obvious in
1:31:13terms of looking at traditional
1:31:15tournament species, which is that
1:31:17females have no choice who they're
1:31:18mating with. It's linear access models.
1:31:21One female winds up with the alpha male,
1:31:23two females, and so on. And this was the
1:31:25dominant model in all of primatology
1:31:28starting in the '60s.
1:31:30And then by around 1980 or so, uh it was
1:31:33recognized that in fact, there's
1:31:34virtually no evidence for strict linear
1:31:37access models of the main determinant of
1:31:40who a female mates with is who's the
1:31:43winner of male-male competitive
1:31:44interactions. People discovered at the
1:31:46time that in fact, there was this
1:31:49strange, strange violation of all these
1:31:52models because it turned out the models
1:31:54were not based on behavior. And this
1:31:56generally was discovered around that
1:31:57time because that was around the time
1:31:59that majority of primatologists on Earth
1:32:01suddenly became female and started
1:32:04looking at the female end of things and
1:32:06discovered that this linear access stuff
1:32:08is not in fact what occurs.
1:32:11And out of that came a completely
1:32:13shocking concept that ran through
1:32:16primatology like a bolt of lightning.
1:32:19The notion that there was this This is
1:32:21the technical term some degree of female
1:32:24choice.
1:32:25Oh, whoa. That's kind of
1:32:29bizarre where females have something to
1:32:31do with who they mate with and there's
1:32:33been a whole world of primatology
1:32:35studies since then showing what female
1:32:37choice is about.
1:32:39First off, how does female choice occur
1:32:42in a typical tournament species? You got
1:32:45this problem. With primates, for
1:32:46example, you wind up with a pair of bond
1:32:49a cons with a consortship between a male
1:32:51and an ovulating female and because it's
1:32:54a tournament species, the male is twice
1:32:56the size or has big huge canines or
1:32:59whatever stuff he's got in there, he is
1:33:01physically able to dominate the female
1:33:04quite readily. You do not see female
1:33:06choice in those cases being exerted by
1:33:08the female beating up on the guy and her
1:33:10getting to go mate with who she's
1:33:12interested in. What you see is much more
1:33:15clever behavior on the part of the
1:33:16female.
1:33:17She will, for example, exhaust the guy.
1:33:21Every time he sits down to feed, the
1:33:23female gets up and starts walking and he
1:33:25has to jump up and, you know, pile
1:33:27together the picnic and go running
1:33:29after. Every time he tries to take a
1:33:30nap, she goes walking. Or what do you
1:33:32find with baboons is the most clever
1:33:35thing that females do is they go walk
1:33:37and lead the male right in front of his
1:33:40worst rival.
1:33:41Or then they'll do it again and again
1:33:43and again and get the guy totally haired
1:33:46out and crazed and at some point those
1:33:48two males will have a fight. And what
1:33:50then happens is she runs off to the
1:33:52bushes and has what is technically
1:33:53called a stolen copulation with the guy
1:33:56she's actually interested in.
1:34:00So, maybe it's not so bad to be a female
1:34:02baboon.
1:34:04So, now what this brings us to insofar
1:34:06as this alternative female strategy is
1:34:09available, we now come to this
1:34:11absolutely critical question, one that
1:34:13has run through the ages, which is what
1:34:15do female baboons want?
1:34:18Who do they want to mate with? And
1:34:21people are not positive, but there's
1:34:23some suggestion in the data. It needs to
1:34:26be replicated more. There's this trend,
1:34:28but there's the suggestion that female
1:34:31baboons like to mate with male baboons
1:34:34who are nice to them.
1:34:36No, are they sure? Are they certain?
1:34:38Have they done their statistics right?
1:34:40Is it big? They go and they mate with
1:34:42guys who groom them a lot. Guys who play
1:34:46with their infants. Guys who, when
1:34:48they're in a bad mood, don't beat up on
1:34:49them, but beat up on somebody else. I
1:34:51mean, this counts as a prince of the
1:34:53male baboon. This is someone you take
1:34:55home to meet mom. When he's in a bad
1:34:56mood, he pummels someone else, not me.
1:34:59This is someone you want to mate with.
1:35:02And in the mid-1980s, excellent
1:35:03primatologist Barbara Smuts of
1:35:05University of Michigan came up with a
1:35:07very jargony scientific term that all
1:35:10sorts of non-human primates have
1:35:12intersexual friendships. And that's not
1:35:14an anthropomorphic term.
1:35:17What it was though was people sort of
1:35:19snickering at it in that the initial
1:35:20notion was that these were just friends.
1:35:23These were platonic monkey
1:35:25relationships. They were not about
1:35:26reproduction, and it was not until
1:35:28people got good enough and enough data
1:35:30to start picking up on all those stolen
1:35:32copulations to see that the females were
1:35:35picking up and mating with their nice
1:35:37guy, "Oh, we're just friends. I could
1:35:39never see my" Whoa, and they're suddenly
1:35:40in the bushes with him, and it suddenly
1:35:43turned from the Yeah, nice guys finish
1:35:45last. Okay, they do lots of grooming,
1:35:47but let's count number of copies of
1:35:48genes to becoming apparent that the
1:35:51being a nice guy was a viable
1:35:53alternative reproductive strategy as
1:35:56long as there was this thing of female
1:35:58choice. And what the paternity studies
1:36:00began to show was that was a very viable
1:36:04alternative strategy in part because
1:36:06you're not mating anywhere near as much
1:36:08if you were a low-ranking affiliative
1:36:10male with a female, you're not mating
1:36:12anywhere mating anywhere near as much as
1:36:14the high-ranking males, but you're not
1:36:17burning out. You're not getting injured.
1:36:18You're not having the male male
1:36:20fighting. You live a lot longer and this
1:36:23keeps happening.
1:36:24There's a problem, though. Which is,
1:36:27suppose you are a female baboon
1:36:30and you want to mate with this nice guy
1:36:32and one of the things that he's nice
1:36:33about is he's nice to your kid who's now
1:36:35about 3-4 years old and there's a very
1:36:38good chance that where that affiliative
1:36:39relationship started with him got
1:36:41jump-started was the fact that he was
1:36:43the most likely father of that kid and
1:36:46has developed somewhat of an affiliative
1:36:47relationship with the kid and hangs out
1:36:49with them and hangs out with you and so
1:36:51you've established this is a nice guy I
1:36:53want to mate with. But there's a
1:36:54problem. Which was if he was the likely
1:36:57father of your now 3-4 year-old
1:36:59offspring, the odds are that 3-4 years
1:37:02ago he was a pretty high-ranking male.
1:37:05And what that means now 3-4 years later
1:37:07is he's likely to be some aging guy over
1:37:10the hill whose rank has been dropping.
1:37:13In other words, not someone who is going
1:37:15to be very effective at male-male
1:37:17competition. And you get this
1:37:19horrible sort of tension there going on
1:37:22between the male-male competitive world
1:37:25generate some Arnold Schwarzenegger jerk
1:37:28who's the one who's supposed to where
1:37:29she wants to mate with Alan Alda or
1:37:31whoever. And what you have then is he's
1:37:34not up to the male-male competitive
1:37:36stuff cuz he's some aging guy and you
1:37:39instead have the world of stolen
1:37:41copulations.
1:37:43So, isn't that great? Isn't that
1:37:45heartwarming? A whole world of what are
1:37:47now called alternative strategies. If
1:37:50you're some scheming male baboon wanting
1:37:52to pass on as many copies of your genes,
1:37:54you may decide the really manipulative
1:37:57thing to do is to be nice to some female
1:38:00and
1:38:00groom her more than she grooms you,
1:38:03which is a very rare thing for a male
1:38:04baboon to do. So, great alternative
1:38:07strategies, very heartwarming.
1:38:10Not so heartwarming.
1:38:12Because there are another other
1:38:14alternative strategies available in some
1:38:16species, alternatives where male sexual
1:38:19behavior is not the outcome of explicit
1:38:22male-male competition, but instead takes
1:38:25an alternative strategy. And you see one
1:38:27example of this in orangutans.
1:38:30Orangutans, great apes, and they've got
1:38:33a very interesting bizarre social
1:38:35system, but what you have is your basic
1:38:38nonetheless sort of familiar picture of
1:38:40male-male competition. Large percentage
1:38:43of orangutan male aggression is built
1:38:45around the reproductive access to
1:38:47females, and you've got a whole world of
1:38:49very peripheralized, low-ranking males
1:38:51who never mate.
1:38:53And there's an interesting physiology
1:38:54that goes along with it. That was the
1:38:56picture that everybody used to have, and
1:38:59then in the 1970s, pioneer researcher in
1:39:02this Biruté Galdikas, who has studied
1:39:05orangs for decades out there in
1:39:06Indonesia, uh she noted something really
1:39:09disturbing, which is low-ranking,
1:39:12non-reproductive male orangs have an
1:39:15alternative mating strategy. What do
1:39:17they do? They rape females. And this was
1:39:20the first introduction of that term into
1:39:22zoology, and that is not an
1:39:24anthropomorphism. If defined as a
1:39:28violent process of mating with a female
1:39:30against her will, this is what goes on
1:39:33in orangutans. A certain percentage of
1:39:36reproduction is low-ranking guys who
1:39:38have no direct access to females as a
1:39:40result of male-male interactions. This
1:39:43is not the nice guy alternative. So,
1:39:45there is precedent for this also. And
1:39:47this is by now very well documented
1:39:49behavior among orangutans.
1:39:52Then, if you want to come up with
1:39:54something very subtle and clever,
1:39:56there's apparently this whole world of
1:39:58fish species where low-ranking males can
1:40:01pretend to be a female and take on
1:40:03female coloration and pretend to be just
1:40:06friends and someone they could pour
1:40:07their heart out to and then suddenly one
1:40:09day they have a penis and where did that
1:40:11come from and everything suddenly
1:40:12changes there. Okay, so we have the very
1:40:15strict boring models. Females invest
1:40:18more calories than males and thus they
1:40:20are much more picky. Males mate with
1:40:22females entirely as a function of
1:40:24male-male competition and thus evolution
1:40:26is driven by male aggression and all of
1:40:29that. Let me just see as people are
1:40:31clearly about to run out the door.
1:40:36For more, please visit us at
1:40:37stanford.edu.

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