topics: |  sex | biology | evolution

Preface:

Among the unusual aspects of human sexuality that I discuss are female menopause, the role of men in human societies, having sex in private, often having sex for fun rather than for procreation, and the expansion of women's breasts even before use in lactation.

The animal with the weirdest sex life (out of 4300 mammals)

[opening lines:] If your dog had your brain and could communicate, and if you asked it what it thought of your sex life, you might be surprised by its response. It would be something like this:

Those disgusting humans have sex any day of the month! Barbara proposes sex even when she knows perfectly well that she isn't fertile — like just after her period. John is eager for sex all the time, without caring whether his efforts could result in a baby or not. But if you want to hear something really gross — Barbara and John kept on having sex while she was pregnant! That's as bad as all the times when John's parents come for a visit, and I can hear them too having sex, although John's mother went through this thing they call menopause years ago. Now she can't have babies anymore, but she still wants sex, and John's father obliges her. What a waste of effort! Here's the weirdest thing of all: Barbara and John, and John's parents, close the bedroom door and have sex in private, instead of doing it in front of their friends like any self-respecting dog!

Why human sex is unusual

a) in most of the 4300 mammal species, male and female meet only to copulate,
   the male rarely contributes to child-raising.  Exceptions include
   polygynous male zebras and gorillas with harems of females, male gibbons
   paired off with females as solitary couples, and saddleback tamarin
   monkeys, of which two adult males are kept as a harem by one polyandrous
   adult female.

b) in most mammal species, female ovulation is widely advertised, (e.g. area
   around the vagina turning bright red, special smells, etc.).

c) Except for a handful of species like bonobo chimps and dolphins, sex is
   only when the female is oestrous.  sex is also expensive - it can cost
   your life to lower the guard, so having it for fun is quite unusual.

d) in most cases, sex is public.  among chimps, a couple may pair off for a
   couple of days, but the female may also have public sex with some other
   male within the same estrus cycle.

d) menopause is not known in the animal kingdom.
   	[   At this point, I thought for a bit if this may not have been a
	recent evolutionary change.  But surely menopause was known in
	ancient times, when life expectancy was 40?  It must have been, for
	many indiv's would have lived to be 80-100.  Hence it is not an
	artifact of the unprecedented rise in human longevity in the last few
	hundred years.  
	   What of the hypothesis that other species may experience it but
	rarely live long enough for us to know? 
	   But I am sure JM has done his homework, so these are probably just
	idle ruminations. - AM]

Battle of the sexes

The male of several species of spiders and mantises is routinely eaten
by his mate just after or even as he is copulating with her. This
cannibalism clearly involves the male's consent, because the male of
these species approaches the female, makes no attempt to escape, and
may even bend his head and thorax toward the female's mouth so that
she may munch her way through most of his body while his abdomen
remains to complete the job of injecting sperm into her.

	
	mating black widow spiders (Latrodectus dahli, native to west asia).  
	the small male is on top.  it makes no attempt to escape; if the
	female is hungry, he will be eaten.  males will try to
	sense the more dangerous females and avoid them.
	(image source: https://entomologymanchester.wordpress.com/2010/07/)


For some species of spiders and mantises living at low population densities,
a male is lucky to encounter a female at all, and such luck is unlikely to
strike twice.  The male's best strategy is to produce as many offspring
bearing his genes as possible out of this lucky find.  The larger a female's
nutritional reserves, the more calories and protein she has available to
transform into eggs.  If the male departed after mating, he would probably2
not find another female and his continued survival would thus be useless.
Instead, by encouraging the female to eat him, he enables her to produce more
eggs bearing his genes.  In addition, a female spider whose mouth is
distracted by munching a male's body allows copulation with the male
genitalia to proceed for a longer time. [p.16-17]

	[Ultimately, in biology, it is only the genes that survive, not the
	organism.  Gives us pause to ponder on the greater purposes of life -
	what's the purpose of reading books and typing in excerpts?]

[but the extreme size diphormism in spiders is caused by many factors.  in
the tarantula Augacephalus junodi, which lives in dry climates with
occasional flooding, the big female lives securely in an underground
burrow.  the more active male has to be a lot smaller so it can survive the
vagaries of climate. (see research by Dmitri Logunov ) ]

Fathers and child-raising: To rear or to desert?--

Most fathers make some contribution to their children, even if it's
just food or defense or land rights.  We take such contribution so
much for granted that they're written into law: divorced fathers owe
child support; an unwed mother can sue a man for child support if
genetic tests prove that he is her child's father. [p.21]

Most male mammals have no involvement with either their offspring or
their offspring's mother after inseminating her; they are too busy
seeking other females to inseminate. [21]

[If] the newly fertilized, laid, or hatched egg has absolutely zero
chance of surviving unless it is cared for by one parent [then] there
is indeed a conflict of interest.  Should one parent succeed in foisting
the obligation of parental care onto the other parent and then going
off in search of a new sex partner, then the foister will have
advanced her or his genetic interests at the expense of the abandoned
parent. [26]

Whether it actually pays you to desert depends on whether you can
count on your old mate to finish rearing the kids, and whether you are
then likely to find a receptive new mate.  [It is as if they are
playing a game of chicken.]  Which parent is more likely to back down?
The answer depends on three considerations: 

  1. which parent has more invested in the fertilized egg; 
  2. whether chances of propagating the genes by finding alternate partners
	is greater than that of looking after the current offspring; and
  3. the parent's confidence in paternity or maternity of the egg. [p.27]

By the end of a nine-month pregnancy a human mother's expenditure of
time and energy is colossal in comparison with her husband's or
boyfriend's pathetically slight investment during the few minutes it
took him to copulate and extrude his one milliliter of sperm. [Leads
to the lactation / guarding of eggs by females.  In organisms where
the inputs are equal, e.g. in external fertilization, the father, if
he is sure of having inseminated the eggs - as in (some frogs or
fish), may also look after the eggs' safety, thus ensuring at least
the survival of those genes. ] [31]

A man produces about two hundred million sperm in one ejaculate -- or
at least a few tens of millions, even if reports of a decline in human
sperm count in recent decades are correct.  By ejaculating once every
28 days during his recent partner's 280-day pregnancy - a frequency of
ejaculation well within the reach of most men -- he would broadcast
enough sperm to fertilize every one of the world's approximately two
billion reproductively mature women.  That is the evolutionary logic
that induces so many men to desert a woman immediately after
impregnating her and to move on to the next woman.  A man who devotes
himself to child care potentially forecloses many alternative
opportunities.  [p.33, Argument 2 from p.27 above]

[Female mammals are confident of paternity, but] Male parental care
would be a bad evolutionary gamble. [34]

Three types of exceptions to male post-copulatory desertion

One type is those species whose eggs are fertilized externally.  The
female ejects her not yet fertilized eggs; the male, hovering nearby
or already grasping the female, spreads his sperm on the eggs; he
immediately scoops up the eggs, before any other males have a chance
to cloud the picture with their sperm; and proceeds to care for the
eggs, completely confident in his paternity. [35]

[Second type - Sex-role-reversal-polyandry] Big females compete
fiercely to acquire a harem of smaller males, for each of which in
turn the female lays a clutch of eggs, and each of which proceeds to
do most or all the work of incubating the eggs and rearing the young.
The best known of these female sultans are the shore birds called
jacanas (alias lily-trotters), Spotted Sandpipers, Wilson's
Phalaropes.  [Reason for reversal - the chicks are precocial, implying
much development in the egg stage; hence a single parent can more
easily raise them; also this is why the females are larger - four eggs
constitute upto 80% of a female sandpiper's weight.  But then since
these are shore birds, there is a high percentage of predation - so
the male is better off if the eggs for some reason are lost, to have
the female rested to do a second round (which she may of course do
with another male also). p.38 ]

Mixed reproductive strategy (MRS) and Extra-pair copulations (EPC)

Third type, like humans, is where the child bearing is so onerous that
a single parent would not be able to do it.  Most birds.  But here
too, most males philander (MRS), and many females are content to be
the second-woman (often, e.g. the Pied Flycatchers, they are tricked)
p.42]

Don Giovanni - seduced 1,003 women in Spain alone - one Spanish woman
every eleven days.  In contrast if a male Pied Flycatcher temporarily
leaveshis mate (for instance, to find food), then on the average
another male enters his territory in ten minutes and copulates with
his mate in thirty-four minutes.  Twenty-nine percent of all observed
copulations prove to be EPC's, and an estimated 24 percent of all
nestlings are 'illegitimate'. [45]

POLYANDRY: Tre-ba society of Tibet

Women with two husbands have as many offsprings as those with one;
polyandry arose to prevent land-division; brothers marry same wife; in
contrast, female phalarope - with one male - 1.3 chicks, two - 2.2, and 3.7
with three (hmmm - third case - data sanity?).  See Nayar's TC p. 75qq]
Polygyny paid off well for nineteenth century Mormon men, whose average
lifetime output of children increased from a mere seven children for Mormon
men with one wife to sixteen or twenty children with two or three wives,
respectively, and to twenty-five for church leaders, who averaged five
wives. [49]

In chromosomes 1 through 22 the two chromosome pairs are identical.
Only chromosome 23 is unpaired and that too only for males - who have
a big chromosome (X) paired with a small one (Y).  Women have two
paired X chromosomes.  Among non-reproductive functions, colour vision
is determined by the X chromosome.  If a Y chromosome is present, the
bet-hedging gonad begins to commit itself in the seventh week to
becoming a testis, but if there is no Y chromosome, the gonad waits
until the thirteenth week to develop a ovary . . . People with one Y
and two X chromoomes turn out most like males, whereas people with
three or just one X chromosome turn out most like females.  [54]

'Being a male is a prolonged, uneasy, and risky venture; it is a kind
of struggle against inherent trends toward femaleness.'
  - endocrinologist Alfred Jost. [55]
	 [endocrnology : study of hormones and their effects, glands
		 that produce hormones, etc.]

embryos also start out hedging with two sets of ducts, known as the
Mullerian ducts and Wolffian ducts.  In the absence of testes, the
Wolffian ducts atrophy, while the Mullerian ducts grow into a female
fetus's uterus, fallopain tubes, and interior vagina.  With testes
present, the opposite happens: androgens stimulate the Wolffian ducts
to grow into a male feturs's seminal fesicles, vas deferens, and
epididymis, and the testicles produce a protein called Mullerian
inhibiting hormone. [58]

[enzyme defects - some male hermaphrodites are more according to the
norms of "female pulchritude" - bigger breasts, long legs,] cases have
turned up repeatedly of beautiful women fashion models not realizing
that they are actually men with a single mutant gene [that prevents an
enzyme creation/function [you found out when you fail to menstruate -
p.60]



(excerpts from WSIF continuess below)

A long set of asides: sexual differentiation in development

Jared Diamond : Turning a man

		Discover Magazine June 1992
		[discovermagazine.com/1992/jun/turningaman62]

Barbara grew up as an apparently normal girl enjoying a happy
childhood. As her teenage years approached, she looked forward to
experiencing the same sexual development she saw in older girls. Gradually,
however, she began to have a vague sense that the expected changes weren’t
happening in her. By the age of 14 she was really worried: she had not yet
menstruated and her breasts showed no signs of growth. What she did have was
a pain in her left groin that eventually subsided, only to be replaced by the
appearance of a mass in the left side of her labia. With growing shock, she
felt her voice dropping, her facial hair growing, and her clitoris enlarging
to become more and more like a penis.

After Barbara's sixteenth birthday, her penis developed erections, she
produced ejaculations, and she found herself feeling a sexual interest in
girls. By now she had become convinced that she was really a boy and that the
mysteriously shifting mass within her was in actuality a testis. But Barbara
still struggled with the problem of how to present herself to her parents and
friends, before whom she avoided being caught naked. She knew they had to
suspect something. When they found out, would they ridicule her--or him--as a
freak?

The vast majority of us are born unmistakably male or female and remain
that way throughout life.

To find one's gender ambiguous or shifting is as cruel a blow as could befall
one's ego. It's as close as any of our children might come to the nightmare
experienced by Gregor Samsa, of Franz Kafka's terrifying story Metamorphosis,
who wakes up one morning to find himself transformed into a human-size
insect.

Sexual Differentiation: genetic trajectory

Between the fifth and seventh week after fertilization, human embryos of
either sex develop an all-purpose gonad that can later become either a testis
or an ovary. If a Y chromosome is present, that all-purpose gonad will begin
to commit itself by the eighth week to becoming a testis. But if there's no Y
chromosome, it waits until the thirteenth week and then begins developing as
an ovary. Thus the natural tendency of our primordial gonad is to develop as
an ovary if nothing intervenes; something special, a Y chromosome, is
required to change it into a testis.

[after this], in the eighth week of gestation the testes begin producing the
hormone testosterone, some of which gets converted into the closely related
substance dihydrotestosterone, or DHT. Such hormones are called
androgens. DHT goes on to convert some all-purpose embryonic structures into
the glans penis, penis shaft, and scrotum. Those same structures would
otherwise develop into their female equivalents: the clitoris, labia minora,
and labia majora.

Embryos also start out with two sets of ducts, known as the Müllerian ducts
and the Wolffian ducts. In the absence of testes the Wolffian ducts atrophy,
while the Müllerian ducts grow into a female's uterus, fallopian tubes, and
the inner part of the vagina. With testes present, the opposite happens:
androgens produced by the testes stimulate the Wolffian ducts to grow into a
male's seminal vesicles, vas deferens, and epididymis. At the same time, a
testicular protein called Müllerian inhibiting factor does what its name
implies:  it prevents the Müllerian ducts from developing into the internal
female organs.

a long series of further biochemical steps, programmed by chromosomes other
than the sex chromosomes, is required to produce all the structures other
than ovaries or testes. Every step involves the synthesis of one enzyme,
specified by one gene. If any one gene is altered by a mutation, the enzyme
for which it's responsible may be defective or absent. Thus, an enzyme defect
may result in a male pseudohermaphrodite, defined as someone with one X and
one Y chromosome, and hence intrinsically male, but with a mixture of both
male and female structures.

examples : two kinds of hermaphrodite

Type I: looks like a normal woman. Indeed, "she" often conforms to
the male ideal of feminine beauty even more than the average woman does
because her breasts tend to be well developed and her legs long and
graceful. Her complexion is usually flawless and she tends to have the added
height of a man. Hence, cases have turned up repeatedly among female fashion
models.

Since this type of pseudohermaphrodite looks like a normal baby girl at birth
and externally undergoes normal development and puberty, the problem isn't
even likely to be recognized until the adolescent consults a doctor over her
failure to begin menstruating. At that point the doctor discovers a simple
reason for that failure:  the patient has no uterus, fallopian tubes, or
upper vagina. Instead, the vagina ends blindly without connecting to a uterus
(although it is generally adequate for intercourse).

Further examination reveals testes that are normal except for being buried in
the groin or labia; they secrete normal testosterone and are programmed by a
normal Y chromosome. In other words, the beautiful model is a male who
happens to have a genetically determined biochemical block in the ability to
respond to testosterone...

That block turns out to be in the cell receptor that would normally bind
testosterone and dihydrotestosterone and thereby enable those androgens to
trigger further steps in the development of male genitals. Take away that
androgen receptor and all you normal male readers might look like beautiful
models, too. Since the pseudohermaphrodites' Y chromosome is normal, the
testes themselves form normally and produce normal Müllerian inhibiting
factor, which acts as it does in any man to forestall development of the
uterus and fallopian tubes. However, the process by which the usual male
machinery is activated by testosterone is interrupted. As a result,
development of the remaining all-purpose embryonic sex organs follows the
female channel by default: female rather than male external genitalia,
atrophy of the Wolffian ducts, and hence no development of male internal
genitalia.

The second type of pseudohermaphrodite is exemplified by the case of
Barbara.  Dozens of similar people suffer from an enzyme defect called
5-alpha-reductase (5AR) deficiency. Like the pseudohermaphrodites with
defective androgen receptors, they are genetically males, with a normal Y
chromosome and testes and normal production of testosterone and Müllerian
inhibiting factor. Because of this inhibiting factor they don't develop a
uterus, fallopian tubes, or the internal part of the vagina. Their external
genitals appear largely female at birth, though they may be somewhat
ambiguous and have some male features; this ambiguity sometimes allows
babies with 5AR deficiency to be recognized at birth. At puberty, however,
many of these children become much more male-like.

Androgen insensitivity syndrome (AIS)

	 http://www.thestudentroom.co.uk/showthread.php?t=1774373
http://jenapincott.wordpress.com/2009/06/01/when-the-perfect-woman-is-genetically-male/

Years ago, in college, I met the perfect woman. Or perhaps a man's idea of
the perfect woman. She had flawless and dewy skin, angular cheekbones, a
cinched waist, milkmaid breasts, long legs, dove-like hands, lush long
hair. Wherever she went, people swiveled their necks and stared. She was a
fantasy, a vision. A goddess.

And she was miserable.

It emerged that the source of her pain was a secret that she kept until she
enrolled in a radical gender studies class. Inspired, she came to terms with
her identity, and in the telling she liberated herself. Her secret was that
she wasn’t technically female. She had a condition known as androgen
insensitivity syndrome (AIS). She was the perfect woman on the outside, and
inside she felt perfectly female. But she was genetically male (XY).

Her story was typical for women with complete AIS. At birth her doctors
didn’t notice any difference in her genitalia. In high school she went from
being a normal girl to an Amazonian queen. She was not only taller than her
peers but curvier, too (some androgens are converted to estrogen which act on
breast tissue). Unlike other girls, she never got acne or grew pubic or
armpit hair (androgens regulate hair growth). She had no body odor. She got
recruited as a runway model, was attracted to men and had many boyfriends
(including a celebrity), and had sex, albeit painfully. But by age sixteen
she didn’t get her period, so her mother brought her to the doctor and an
astonishing discovery was made. She had undescended testes. Inside, she
appeared male: no fallopian tubes, no uterus, no ovaries.

This gorgeous college student had complete androgen insensitivity
syndrome. Women with this condition — approximately 1 in 20,000 — tend to be
exceptionally tall and striking in appearance. AIS is caused by a recessive
variant of the gene that codes for Androgen Receptor. Because the body is
insensitive to the androgen testosterone, the usual male features — penis,
testes, scrotum, etc. — are unable to develop. The default phenotype is
female, so people with AIS have a vagina or "vaginal pouch" (although most
AIS women require surgical expansion). If a woman with AIS were to get a
blood test, her testosterone levels would be as high as any man's, but her
body can’t process the hormone. That's why women with complete AIS are so
feminine — arguably more so than other women. (Some people with AIS have only
partial androgen insensitivity. Considered intersex, or hermaphrodites, they
fall all along the spectrum between typically male and female and have a
micropenis. Naturally, there's much controversy about gender assignment at
birth and estrogen or testosterone injections at puberty.)

10 Gorgeous Women (Who Were Born Male)

from http://www.oddee.com/item_98035.aspx 1/11/2012

transsexual models are popping up in magazines and on runways
everywhere. These gorgeous models look and feel like women but were born
with male reproductive organs.


* Andrej Pejic:
  	Serbian Australian model.  In January 2011's Paris fashion
	shows he walked both the men's and women's shows for Jean-Paul
	Gaultier and the men's shows for Marc Jacobs. He has also ranked #18
	on the models.com Top 50 Male Models list while simultaneously being
	ranked #98 in FHM's "100 Sexiest Women in the World



* Lea T.
	Brazilian Lea T. was born Leandro Cerezo in 1981, but that didn't
	stop her from becoming one of the most famous transsexual fashion
	models in the industry today. Lea has been called the muse of high
	fashion design house Givenchy.
		http://i.huffpost.com/gadgets/slideshows/27698/slide_27698_286148_huge.jpg

* Claudia Charriez

	a top international model, Charriez was kicked off of America's Next
	Top Model and The Janice Dickinson Modeling Agency TV shows in 2008,
	but went on to win the America's Next Top Transsexual Model contest
	on The Tyra Banks Show later that year.
		http://transgriot.blogspot.com/2008/08/claudia-charriez-speaks.html
		http://photos.modelmayhem.com/photos/100429/11/4bd9cc6e45a7f.jpg

* Isis King

	Born Darrell Walls in 1985, American model Isis King gained notoriety
	when she became the first transgender contestant ever to appear on
	the modeling reality show America's Next Top Model.

		http://antm411.files.wordpress.com/2010/01/antm_isis01.jpg

* Florencia De La V

	Argentinian Florencia De La V b. 1976 as Roberto Carlos has gone on
	to be one of the most recognizable transgendered actresses in the
	world.  is currently married to a man and the mother to twin babies
	conceived via surrogate.
	In 2010, after a court decision, Trinidad was legally recognized as a
	woman, and changed her name.

* Sirapassorn Atthayakorn [Thailand]

	was named Miss International Queen in 2011's pageant.
		http://www.missinternationalqueen.com/index.htm

* Chamila Asanka (Sri Lankan, a.k.a. Chami)
	
	an up-and-comer in the world fashion industry. A 2011
	contestant in the Miss International Queen pageant.
		http://srilankanmodels.picshuts.com/wp-content/uploads/2011/01/Chamila-Asanka_12_srilankanmodels.picshuts.com_.jpg


* Caroline "Tula" Cossey (England)
	had a small role in the James Bond movie The Living Daylights, posed
	for Playboy, and wrote an autobiography called "I Am A Woman."
	Caroline Cossey
		http://1.bp.blogspot.com/_KCRRRCnjIXE/TNnFKHDl8aI/AAAAAAAAAIc/g9GjtWizZ70/s1600/caroline+cossey+tula_01.jpg


* Roberta Close
	Brazilian model Roberta Close was the first pre-operative transsexual
	model to pose for the Brazilian edition of Playboy magazine. After
	undergoing gender reassignment surgery in 1989, Close posed nude for
	a Brazilian men's magazine called Sexy and was then voted "Most
	Beautiful Woman in Brazil."
		http://24.media.tumblr.com/tumblr_ldq5ybb44J1qe4m1ko1_500.jpg

* India's Malika
	has undergone four surgeries to become the woman she feels she was
	meant to be at birth. In 2011 she became the first Indian to be
	chosen to compete in the annual Miss International Queen competition
	in Thailand, a beauty pageant for transgendered people.
		http://indiatoday.intoday.in/story/tamil-nadu-transgender-malika-in-pattaya-beauty-pageant/1/155032.html

Anatomy and function of the male and female genitalia

	Roy J Levin and Nether Edge, 2007
	The human sexual response - similarities and differences in the
	Anatomy and function of the male and female genitalia
	http://www.indiana.edu/~kinres/chapters/Levin.pdf
		J. The psychophysiology of sex (2007): 35-56.

There has always been a fascination to compare and contrast the human male and
female genitals that at first sight appear so very different.
Despite the obvious external differences, an early anatomical portrayal of
the female vagina was surprisingly drawn as being like the male's elongated
penis but turned inside out!

However, it was not until quite recent times with the discoveries of the
human X and Y chromosomes and the study of the development of the fertilised
mammalian egg that the mammalian male and female genitalia differentiation
[began to be understood. Both start] from the same primitive tissue (the
genital anlagen) was driven differently by the Y chromosome which encodes a
gene referred to as TDF (testis determining factor) which initiates the
conversion of the indifferent foetal gonad (the ovo-testis) into a functional
testis locally secreting the Antimullerian Factor to prevent the development
of the female Mullerian duct system and systemic testosterone to maintain and
develop the male Wollfian duct system and the external genitalia (Jost 1973,
Wilson 1978).

the Y chromosome which encodes a gene referred to as TDF (testis determining
factor) which initiates the conversion of the indifferent foetal gonad (the
ovo-testis) into a functional testis locally secreting the Antimullerian
Factor to prevent the development of the female Mullerian duct system and
systemic testosterone to maintain and develop the male Wollfian duct system
and the external genitalia ( Jost 1973, Wilson 1978).

In the absence of the Y chromosome the testis determining pathway is not
initiated and the ovotestis develops as an ovary and the foetal
differentiation takes the female route. Female development can be regarded as
the default model, it is the basic pattern onto which the male
differentiation is impressed, even the presence of oestrogen is not thought
of as necessary for the female genitalia to develop (Jost 1973, Wilson 1978)

Wilson J (1978) Sexual differentiation. Ann Rev Physiol l40:279-308.
Jost A (1973) Becoming male. Adv Biosci 10, 3-13.

---

How to make the least bad choice in children with ambiguous genitalia

	Possible determinants of sexual identity: How to make the least bad
	choice in children with ambiguous genitalia
	P.D.E. Mouriquand
	BJU International Journal, v. 93, s3, pages 1–2, May 2004
	http://onlinelibrary.wiley.com/doi/10.1111/j.1464-410X.2004.04701.x/full

the genetic sex of the child affects gonadal differentiation. For
primitive surgeons as we are, it appeared that there are four categories of
fetuses; the normal 46XY and the normal 46XX at each end of the spectrum,
and in the middle the Y-deficient fetus and the X-deficient fetus. Clearly
the ‘Y-deficient’ child with abnormal gonads and insufficient virilization
represents one of the most difficult situations in determining the sex of
rearing. 

How can a male fetus be virilized in the extraordinary bath of oestrogen in
which he lives for 9 months? We all read the fascinating experiments by Jost
[1] last century on the role of testicular tissue in sexual differentiation
but still the fetal ‘hormonal factory’ remains full of mysteries. The
placenta certainly has a key role, as shown in the example of twin boys, one
with hypospadias the other with normal external genitalia [2]. Very young
mothers and ‘old’ mothers seem to be more at risk of having babies with
abnormal genitalia [3]. Babies with a low birth weight are more prone to
present the same anomaly. The common denominator could be a placental
deficiency.

It is postulated that the rise of testicular androgen secretion during the
perinatal period could be the determinant to ‘sexualize’ the brain. However,
I recently operated on a 29-year-old African (46XX) patient with congenital
adrenal hyperplasia, no breasts, a hairy chest and beard, a very large
clitoris and no vaginal opening. She was brought to my clinic by a
humanitarian organization who noticed that she was rejected from her
community in Africa. Although she had been bathed in high testosterone levels
for 29 years, she felt as if she were female and asked for reconstructive
surgery. This example shows that high testosterone levels are not sufficient
to determine sexual inclination.

The third factor which may influence sexual behaviour is external genital
appearance. For generations of doctors, creating a penis or an intercourse
conduit (i.e. a vagina) was the main determining factor to establish a
‘sexual identity’. With experience and longer follow-up we know that this is
not certain and several patients rebelled against this rather primitive
concept.

Clearly it is easier for the surgeon to create a female appearance with a
genital conduit rather than a decent organ from a poor penis. Stimulating the
genital tubercle by giving high doses of testosterone remains a standard
method to establish the growing potential of the penis. If the response is
poor, many will orientate the child to a female image, and if it is good they
will choose the male gender. The long-term studies by Schober (Reilly) and
Woodhouse [4] seem to show that male patients with small penises are quite
happy with their sexual life and it might be wrong to orientate a child to
the female gender just because his penis has poor growth potential. Moreover,
the long-term consequences of these hormonal stimulations on the bone, brain
and gonadal development are essentially unknown. How much harm is caused to
patients with partial insensitivity syndrome who receive hormones to
stimulate the growth of the genital tubercle?



						[continuing with WSIF]

Lactation - male and female p.62-70

surrogate mothers can produce some milk within three or four weeks:
earlier, put the infant or a puppy to the breast repeatedly (e.g. mother
wanting to replace sickly daughter).  Modern times - breast pump every few
hours in preparation.  ]

Breast development occurs commonly and spontaneous lactation
occasionally, in men recovering from starvation.  Thousands of cases
were recorded in prisoners of war released from concentration camps
after WWII - five hundred in survivors of one Japanese POW camp
alone. Starvation inhibits not only the hormones, but also the liver,
which destroys the hormones.  When normal nutrition is resumed, the
glands producing hormones recover much faster than the liver. [66-7]

[Dyak fruit bats - may have males and females nursing the baby 67-8]

PREDICTION:  Human male lactation:
Paternity buttressed by DNA testing will make expectant fathers to make
milk via breast stimulation and hormonal injections.  [Will promote] a type
of emotional bonding of father to child now available only to women.  Many
men, in fact, are jealous of the special bond arising from breast-feeding,
whose traditional restriction to mothers makes men feel excluded.

. . . Many of us choose to renounce murder, rape, and genocide,
despite their advantages as a means for transmitting our genes, and
despite their widespread occurrence among other animal species and
earlier human societies.  Will male lactation become another such
counter-evolutionary choice? [80-81]

Evolutionary Cycles

fins of ancestral fishes --> legs in reptiles, birds, mammals; front
     legs --> bird wings,
bird wings --> penguin flippers,
mammal legs --> whale flippers
Similarly, concealed ovulation, boldly advertised ovulation, monogamy,
harems, promiscuity, etc have repeatedly been transmuted into each
other, reinvented and lost. [114]

Hunting was not for food

[Studies on Paraguay's Northern Ache Indians by Kristen Hawkes of
U. Utah: Hunters bring in 9.6Kcals on avg for the 10K by the woman.
While the peak for hunters is much higher - 40K for the occasional
peccary, the median, at 4.7K is much less, and] the Ache' men would do
better in the long run by sticking to the unheroic 'woman's job' of
pounding palms than by their devotion to the excitement of the chase.

Real reasons may be social standing:
Ache' women, asked to name the potential fathers of 66 children, named an
average of 2.1 men per child [their sex partners at the time of
conception).  Good hunters were named more often than poor hunters.

Reproductive strategies for males - 'provider' vs 'showoff' - showoff
is better - why?  Women prefer the provider for husband, but may trade
EPC with the showoff for the occasional extra meat. [130]

Time budget studies show that American working women spend on the
average twice as many hours on their responsibilities.  When husbands
are asked, they tend to overestimate their own hours and to
understimate their wives hours.  That is why the question
	 What are men good for?
continues to be debated within our societies. [135]

Animal signalling

appeal to the opposite sex may depend on specific parts of the body,
as is well known for humans.  In an experimenting demonstrating this
point, the tails of male Long-Tailed Widowbirds, an African species in
which the male's sixteen inch tail was suspected of playing a role in
attracting females, were lengthened or shortened.  It turns out that a
male whose tail is experimentally cut down to six inches attracts few
mates, while a male with a tail extended to twenty-six inches by
attaching an extra piece with glue attracts extra mates.  [171]

The Great Tit has a white stripe on the breast which serves as a
signal of social status.  Experiments with radio-controlled tit models
placed at bird feeders show that  live tits flying into the feeder
retreat if and only if the model's stripe is wider than the
intruder's.  . . . Why should a perfectly good Great Tit retreat from
food just because it sees another bird with a slightly wider black
stripe?  [Unlikely to imply intimidating strength; can lead to genetic
movement towards increadingly thicker stripes.]  These questions are
still unresolved. [172]

Truth in advertising

Signals such as throwing away money (indicative of wealth), or a
peacock's extra long tail are evolutionarily useful, and are not only
honest signals, that inferior animals could not afford [Amos Zahavi]
but also favouring survival, or being closely linked to traits
  favouring survival [Brown and Brown]. e.g. large antlers in deer -
need bio-energy resources - but also help in fighting off other
males.  ] 175

Human signals include faces, smells, hair color, men's beards, and
women's breasts.  What makes those structures less ludicrous than a
long tail as grounds for selecting a spouse?  If we think that we have
a signaling system immune to cheating why do so many people resort to
makeup, hair dyes, and breast augmentation?  [177] . . . we humans
still carry the legacy of hundreds of millions of years of vertebrate
evolution engraved deeply into our sexuality.  Over that legacy, our
art, language, and culture have only recently added a veneer. [191]

[Three honest measures of individual capability in humans: muscles
(more useful than antlers), facial beauty (face is expressive; age,
malnutrition, and injury shows quickest on face), woman's body fat
(needed for lactation, indicative of surplus resources). 180-1]

[Location of excess fat in breasts and hips - can't be on limbs,
therefore torso.  Where on torso can vary - more on buttocks for some
groups - e.g. women of the andaman island tribes - but excess fat on
the lactation region is significant - it acts as a deceptive signal of
lactation capability. 183]

Human runaway signal: penis

At first we seem devoid of exaggerated signaling structures comparable
to a widowbird's sixteen-inch tail.  On reflection, however, I wonder
whether we actually do sport such a structure: a man's penis.  [
187: Evidence - differences with apes; what men "want" (phallocarps 2
ft long; ), ] In response to my question as to why they wore
phallocarps, the Ketebangans replied that they felt naked and immodest
without them. . . . they were otherwise completely naked and left even
their testes exposed. . . . Starting from a 1.5 inch ancestral ape
penis similar to the penis of a modern gorilla or orangutan, the human
penis increased in length by a runaway process, conveying an advantage
to its owner as an increasingly conspicuous signal of virility. [Who
is it intended for - may be for male dominance as much as for
attracting females (which is doubtful) -190]

Contents

   1. The animal with the weirdest sex life
   2. Battle of the sexes
   3. Why don't men breast-feed their babies? The non-evolution of
	male lactation
   4. Wrong time for love: the evolution of recreational sex
   5. What are men good for? The evolution of men's roles
   6. Making more by making less: the evolution of female menopause
   7. Truth in advertising: the evolution of body signals.

--- blurb:
Why are humans one of the few species to have sex in private? Why do humans
have sex any day of the month or year — including when the female is pregnant,
beyond her reproductive years, or between her fertile cycles? Why are human
females the only mammals to go through menopause? Why is the human penis so
unnecessarily large? Why do we differ so radically in these and other
important aspects of our sexuality from our closest animal relatives and
ancestors?With wit and fascinating scientific expertise, the author of The
The Third Chimpanzee explores the mystifying evolutionary forces that gave shape
to our sexual distinctions and shows how they contributed to what it means to