[BITS] Sex on the Brain, Deborah Blum

Rohit Khare -- UC Irvine -- 4K Associates -- +1- (rohit@fdr.ICS.uci.edu)
Fri, 17 Jul 1998 13:09:23 -0700

Sex on the Brain

Deborah Blum

Penguin, 1997

A highly recommended collage of science writing on the multifarious
biological differences between men and women: anthropology,
endicronology, generic, sociology, &c. Current scientific thinking
about emotion, intelligence, power, monogamy, and rape. Comparisons to
many nonhuman species for perspective.

Things I marked down:

"Why the hell does the Y chromosone end up as a little blob with
hardly any genetic activity on it?" evolutionary bilogist Jim Bull

The XX female makeup is more stable it has a "backup" copy. The Y
*only* codes maleness.

"If you are XY theres no alternate. The male is stuck, which is why
men suffer more X-linked disorders: color-blindness, hemophilia,
Duchenne muscular dystrophy, and fragile-X retardation. There are more
than 200 of these disorders, and they all occur more often in men than

Trivia: fruitflies male is X; female is XX; no Y.

Gorilla penises average 1.25 inches. "So why, exactly, does a human
male need five inches or greater? somewhere in our past, this was a
threat display [speculation]"

No adequate explanation of the shape of womens breasts: nothing of the
fat deposits is necessary to milk production (after all, males can
lactate, too) yet nearly universally arousing to humans.

Throughout the book, there are illuminating references to
out-of-sample cases: XX males, XXY females, over testosteroned
females, undertestostereoned males, ambiguously gendered infants, you
name it. In a small group of villages in the Dominican Republic,
theres a developmental oddity of "male" children with undescended
testes and clitoris-sized pensies until they reach puberty, the
process completes, and they are transformed from female to male in the
culture without comment. Called guevedoces eggs/testes at twelve, in

Sexual dimorphism in the brain has been the holy grail: can we prove
that men and women think differently? Songbirds, for example, have a
male vocal center six times larger, the better to seduce.

"The agression rate in female chimpanzees is 1/20th the male."

"So, in the rush for apples, the females were the grabbiest. They were
also the worst losers. In almost half the fights between males [rhesus
macaques], friendly contact was reestablished in half an hour." Female
rate: 18% within 30 min. "females reconcile in less obvious ways, that
they use subtler forms of contact than friendly shoulder-punch style.
Or it may be that nurse grudges a whole lot better."

Depression can be passed from mother to infants PET scans show it.

"What we say about prairie voles is that theyll sleep with anyone, but
theyll only sit by their mates."

"In a world dominated by polygamy in which 97% of mammals live by the
rules of promiscuity it doesnt seem surprising that total fidelity is
elusive. After all, reproductive success is about what works."

"only mongamous species build solid, and even equal, male-female

Darwin: "A girl sees a handsome man and, without even observing
whether his nose of whiskers are a tenth of an inch longer or shorter
than some other man, admires his appearance and says she will marry
him. So, I suppose, with the peahen [and the peacock]"

"Scientists can pick out the studs easily on sight, by their clean-cut
look. As with humans, horseshoe crabs will lose their glossy, smooth
appearance with age."

LOTS of reasons to marry young females. Downs odds, for example: 1167
to 1 at 20, 385 to 1 at 35, 106 to 1 at 40. Breast cancer rates double
for first-child-after-30 vs before-20 (of course, breast cancer kill
50k American women per year; heart disease kills 480k!). Could also
explain blonde-preference, since blondeness fades with age.

"in general, monogamy doesnts seem to support show-and-tell looks.
Species that pick a life partner seem remarkably unimpressed by vulgar
tailfeather displays or muscle-bund competitions." [Whew!]

polygamy is proportional to dimorphism the degree of physical
difference between the genders.

South American titi monkeys: monomorphic, very monogamous: "take
almost two hours to get to sleep at night, the male and female
checking out the others wishes and wants with such thoroughness they
can can only inch towards sleep so wedded to each other than their
offspring come a distant second." They can test that last by measuring
cortisol, which leaps on mate separation and budges not on stealing an

Paternity/loss of virginity can remap the male brain in the California
mouse. By the time a baby is born, all kinds of nesting behaviors
emerge and the brain cells change distribution.

There are aphsodisacs for sex; there are even hormones for
relationships: oxytocin and vasopressin. Can trick males into bonding
immediately even with sterile females with oxytocin, and vice versa.
Those hormones are the main difference between mono and ploy vole
species: oxytocin (in females) and vasopressin (in males) rise with
picking a life partner, and again with kids. In humans, the links are
weaker; oxytocin floods both genders on orgasm.

300k years ago, male humans were 2x the size; now only 17% larger, so
perhaps we are converging on monogamy.

David Buss conducted a 33-country survey of what men and women want in
a mate. Both rated "kindness" and "intelligence" at the top of the
scale. "While women found dominant, high-status men as sexually
attractive, they didnt find them so appealing as companions giving
them low marks on warmth, tenderness, and likability."

As for men, researchers put out two identical personal ads one a
recovering drug addict, and one fifty pounds overweight, 80% of the
respondeds went for the addict. International survey of personals, in
turn, found that women were five times more likely to request partners
to have money.

"Overall, fathers rough-and-tumble more with their children; they
tease them more; they play harder and tend to emphasize physical
challenge more." Israeli fathers are dramatically less involved: one
caretaking task and 45 minutes a day of contact on average. The more
involved fathers are, the higher their opinion of their children at 3
yrs. and the higher the actual achivement years later.

Hard numbers on homosexuality: 2-3% of males, 1.5% of females on a
regular basis. One-night-stands, ever, doubles the ratios. Widen it to
self-reported "fantasy", and it gets to 8.7% of men, 11.1% of women.
Hmmm. Thats a lot of lesbian fantasies

At last count, 63 species show evidence of male-male contact. "Almost
in every case a passing variation" Sheep are the one well-studied
exception. There are consistent life-time gay rams.

Interesting evolutionary biologists theories about gay men as the true
nature of male sexuality, unfettered by women. Darryl Bem: "Suppose
you went up to your average single heterosexual male and said theres
this new institution called a bathhouse, and its full of young women
who want sex, who are wearing only towels. Its safe sex, and theres no
exploitation. What do you think would happen?" Blum: "Theyd be
standing in line but most woment would reply that theyd rather know
who they were going to bed with." Bem: "the right-wings objection has
nothing to do with orientation at all objection to the way men behave
compared to women."

In fact, lesbians engage in sex less often than couples with one or
two men.

Full gender awareness arrives between two and three years old. At
three, friends are half-and-half; by 5, 20%; by 7 years, almost no
good friendships cross gender lines.

Gay men, lesbians, and hets on two skill tests: throw ball at target
and peg-in-hole; gross and fine motor control. Traditionally, men are
better at the former, women the latter. A: gay men consistently threw
less accurately than straights. Lesbians did better than straight
women. On the pegs, women beat men regardless.

Current estimates of genetic influence: explains 50% of
extroversion/shyness, 10% of self-esteem, up to 70% of intelligence.

Female rats, given testosterone at birth, develop penises and "know"
how to use them; block it in males, the penis fails to develop and
they wander around without sexual drives.

The fetal testosterone bath controls a wide variety of triggered
mechanisms in forming gender.

Chimps: T-levels measurably spike on sight of an attractive female;
rise 20% for a day after winning a fight , fall 90% on loss for even
longer same for tennis players. Chimps watching other monkeys have sex
= 400% increase in T. High-T weakens the immune system, contributing
the general fragility/disposability/expendability of males.

We already have a simple genetic test for predisposition to violence:
the human Y is 7x more likely to be arrested.

In a multigenerational study with Kaiser Permanente, they measured
"feminism" mothers and daughters passing down beliefs about work,
competition, and family versus background testosterone levels.
Consistent match. High-T women: fewer kids. Low-T like makeup,
jewelry, cooking, decorating more. High-T is heritable, whether by
nature or nurture is unknown.

Estrogen is from the Greek root for frenzy. After all, "hysteria" is
Greek for "suffering in the womb."

Remember that story about how women rated mens sweaty shirts sexier if
they had different histocompatibility complexes (diverse immune
responses)? The Pill completely reverses that sense. The Pill also
flattens "interest" in self-reported diaries, which rose near
ovulation in the control group. The Pill correlated with less arousal
by pictures of nude bodies or children.

Another test: Orangutan males are always "on" Connected the male and
female cages by a door small enough only females could "choose" to
mate and while there were occasional looks, sex only occurred at
ovulation. Period. [Oooh bad pun!]

With chimps, the Pill steadily reduced sex for 7 of the 9 couples; one
had a great relationship, and sex continued apace; the last was a
dominating, dysfunctional one which also withered. Moral: the Pill
puts "control" back in female hands, and then the relationship-quality
wins out.

Found ten ovariectomized (i.e. no estradiol) macaques at Emory; had
been a close-knit group, then reintroduced to adolescent males after
six years. Waited for animals to become friendly. And waited. 2.5
years later, still not on speaking terms. Estradiol injections
recreated society in three days. In a single weekend, grooming,
pairing; mating within the week. Estradiol controls female desire,
open-and-shut, right?

Guiness records: male with 888 kids (Mongolian overlord of ancient
China); female was 18th century Russian with 69 (many triplets). Right
there is a genetic loophole for forced sex

"Its sometimes tempting, when thinking about human behavior, to simply
declare the whole subject to be complicated to the point of
hopelessness. Rape strikes me this way. Is it rape if a nonsexual
instrument is used? If the victim isnt even old enough to crawl? When
I was a very new reporter, covering the police beat in northern
Georgia, I had to write a story about a 21-year old father who
critically injured his one-month-old daughter by shoving a pair of
scissors into her vagina. Do we count that as rape, rage, or pure
psychotic insanity? Of course, there is a sexual connotation to this
act. But who was he angry with, the child or her mother? Theres pure
violence in both; theres power at stake; and theres the element of
sex. They dont separate so easily."

Randy Thornhills advanced sociobiology class at UNM: "Essentially, all
males, in the right circumstance, respond to forced sex."

Oregon was the first state, in the late 70s, to outlaw marriage as a
defense against rape charges. California adopted the rule in 1979; one
state senator commented on the floor, "If you cant rape your wife, who
can you rape?"

US rape rates are 2x Canada; 3x UK, Germany, Sweden, Denmark; and
5-10x France, Holand, Belgium, Japan. That rate is 70 per 100,000
women per year; attempts might be 3x. [Still, that means
statistically, 30 year cumulative exposure would be about 2% of women
raped in a lifetime does that jibe with the activist communitys

Theres one species definitely without rape: Bonobo monkeys. "
spectacularly promiscuous. Lets talk continuously receptive here, and
I mean males *and* females. Bonobos weave sex into all aspects of
their lives: males mound females; sometimes females sit astride males;
femalses rub other female genitals for fun; males to the dame;
duvenile monkeys suck each others genitals; all bonobos French-kiss;
and sex between two bonobos is an open invitation for othes to amble
up and insert an additional finger or toe into an orifice. Sex is for
reproduction, for fun, for gratitude, for friendship exuberantly
shared and enjoyed by all."

On that note,


Rohit Khare -- UC Irvine -- 4K Associates -- +1-(626) 806-7574
http://www.ics.uci.edu/~rohit -- http://xent.ics.uci.edu/~FoRK