20 Things You Didn't Know About... Sex
Why love songs can be
deadly, why male spiders wrap their romantic gifts, and why we have sex in the
first place
1 Marvin Gaye
breaks it down in “Let’s Get
It On”—what
could be simpler? Psychologists at the University of Texas at Austin take a
different view. They
surveyed 444 people [pdf]
and found 237 reasons why people have sex.
2 “I was drunk”
made the top 50 for women; “to get a favor” made the top 50 for men.
4 The standard
evolutionary argument is that the mixing of DNA between two members of a
species introduces more variation into the gene pool. But asexual reproduction
is far more efficient.
5 One leading
hypothesis suggests that sex won out over DIY as a defense
against parasites,
which would be less harmful in a varied gene pool.
6 In 2009 a team
of scientists bolstered this idea by monitoring two groups of snails—one that
reproduced sexually, the other asexually. Over time, the self-starters became
more susceptible to parasites, dying off at a faster rate.
7 Not that sexual
reproduction is exactly disease free. About 3.7 million Americans carry the
most common sexually transmitted parasite, Trichomonas
vaginalis.
8 You think we’ve got
troubles? The mating call of certain Hawaiian male crickets attracts a
fly that deposits parasitic larvae. When the larvae mature, they burst
out of the cricket, killing it instantly.
9 Some male crickets
have a mutation
that prevents them from making the call, helping them elude the deadly flies.
The sneaky-quiet ones hang out around the vulnerable singing crickets so they
can still meet girls.
10 One of nature’s
most elaborate mating rituals belongs to the nursery web spider. Males wrap a
collection of gifts—typically edible insects—in silk bundles and present them
to potential mates.
11 In some cases,
male spiders try to sneak in worthless items like the leftovers of
already-eaten bugs, so females have learned to examine the gift. Danish
researchers found that far greater
success was awarded to males who had a nicely wrapped package.
12 When the mood strikes
a male Muscovy duck, the corkscrew-shaped embodiment of its excitement shoots to a
fully extended 8-plus inches in just 0.36 second.
13 Battle of
the sexes:
The corresponding female organ is also corkscrewed—but in the opposite
direction.
14 Studies of
human male inflation, a.k.a. “phallometry,” often use a sealed, gas-filled
cylindrical chamber that fits snugly around the object of interest and
registers the amount of gas displaced.
15 Equivalent
studies in women use a photo-plethysmograph, a probe that
measures pulse and changes in blood volume in the vagina.
16 Psychologist Meredith
Chivers
of Queens University in Ontario, Canada, used similar devices to study
objectively how men and women responded to erotic films. Heterosexual men, as
well as homosexual men and women, became aroused while viewing attractive
members of their preferred sex engaged in nonsexual activities, such as walking
on a beach. For heterosexual women, a naked strolling guy didn’t do much.
17 Yet Chivers
found that women exhibited increased blood flow when watching bonobos mate,
even though they did not report feeling aroused.
18 Chivers
speculates that increased blood flow (and associated lubrication) in response
to witnessed sexual behavior could be a biological response that prepares
females for sudden, unsolicited penetration.
19 Ohio State University
psychologist Terri Fisher tested the
oft-repeated claim
that men think about sex every seven seconds (which translates to 8,000
instances daily) by having 283 students carry around a golf-score counter and
click each time they thought about sex, food, or sleep. In reality, the young
men’s fancy turned to sex merely 19 times per day.
20 The young women in
the study had 10 such daily thoughts, on average, and both genders thought
about food and sleep just as often as sex.
Gregory Mone is the
author of the new novel Dangerous
Waters: An Adventure on Titanic. There is no sex in
the story.
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