Science of Love, Sex, and Babies

Who’s Turned On By Pregnant Women?

Posted in parenting, pregnancy, psychology, science, sex by jenapincott on September 26, 2011

 

Early one evening late in my second trimester of pregnancy, I was standing in the dairy aisle of the grocery store, with one hand on my back and the other over the kicking baby in my distended belly. A young man approached me, initiated a conversation about the World Cup, and, casually, asked me if I’d like watch the game with him that weekend. “You’re pretty!” he whispered. I was shocked.

I wasn’t putting out a sexy vibe. (Not at all.) I had assumed that any male attention I receive in late pregnancy, including that from my husband, would be friendly, not sexual. Why would a man who is not the expectant father think pregnancy is sexy? But then other women told me similar stories about how they got hit on in third trimester. So I decided to look into it, and it turns out that a study on sexual attraction to pregnancy has recently come out.

A team of Swedish and Italian doctors, led by Emmanuele Jannini and Magnus Enquist, recruited nearly 2,200 men who had joined online fetish groups such as alt.sex.fetish and alt.sex.fetish.breastmilk. They presented a questionnaire that asked the respondents questions about their preferences for pregnant and lactating women. The survey also asked for the sex and age of each sibling, and whether the sibling is a full sibling or not (half-sibling or adopted child). Most respondents reported both a pregnancy and a lactation preference. The average age at which respondents became aware of their preference was about 18 years.

What Jannini and Enquist and their colleagues were searching for was evidence that there was something special about the upbringing of men that are secually aroused by pregnancy. They knew that a specific stimulus early in life can elicit sexual behavior when theat animal reaches sexual maturity. For instance, goats that are raised by sheep are sexually aaroused by sheep only. This is called sexual imprinting.

Is it possible that boys that are raised by women who are pregnant for much of their childhoods are unusually attracted to pregnant women?

It turns out, what’s good for the goat is good for the guy. The more exposed a man was to his mother being pregnant and breastfeeding when he was between 1.5 and 5 years old, the more likely he is, as an adult, to be sexually attracted to pregnant and breastfeeding women.

A younger sibling is the key to early exposure. The respondents who eroticized pregnancy and breastfeeding had significantly more younger siblings than expected by chance. Respondents with one sibling were older than their sister or brother in 66 percent of cases. Interstingly, siblings born of a different mother does not appear to be related to respondents’ sexual preferences. Only a boy’s own pregnant mother seemed to leave a sexual imprint.

Freud’s “oedipal phase,” from about 3 to about 5-6 years of age, only overlaps partially with the sensitive period suggested by this study’s data, the researchers are careful to point out. Sexual imprinting is different in that it’s motivated not by sexual drive but because the individual learns what’s normal during a sensitive phase of development and later seeks sexual partners that resemble his (or her) own parents.

What does this mean for women who are pregnant or plan to be pregnant? It means you may be able to predict how attracted your partner will be to you in late pregnancy. Does he have sibling born within five years after him? If so, he’s likelier to be turned on by your pregnant self.

As for the guy I met in the dairy aisle, I’d wager he had a younger brother or sister. I’d bet more on getting this right than the winner of the next World Cup.

 *If you like this blog, click here for previous posts and here to read a description of my most recent book, Do Gentlemen Really Prefer Blondes?, on the science behind love, sex, and attraction. If you wish, check out my forthcoming book, available October 11,  Do Chocolate Lovers Have Sweeter Babies?: The Surprising Science of Pregnancy. 

 

 

 

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Do You Live Less if Your Mom Was Stressed?

Posted in parenting, pregnancy, psychology, science, sex by jenapincott on August 12, 2011

Not long ago, a handful of scientists at the University of California at Irvine were curious about why some people live longer than others — even within groups that have similar ethnic and educational backgrounds, demographic and disease risk profiles, and are exposed to similar stressors in life.  At heart, they know the question is impossible to answer.  People are complex. The effects of life events on our genes—what we eat, what we breathe, who we love and how well we’re loved, and so on —are impossible to isolate.

But the scientists had a hunch that some of us had a bad start —beginning in the womb — because our mothers were highly stressed during pregnancy.   There’s an avalanche of evidence that women who are under extreme duress in pregnancy have kids who have shorter attention spans, lower IQ, memory deficiencies, and health problems.  

Could prenatal stress also set a baby’s life expectancy clock to tick faster?

One way to find out is to look at the genes of people whose mothers were extremely stressed during pregnancy. In each of our cells are DNA-protein complexes called telomeres, which cap the end of chromosomes.  Telomeres are like the plastic bit at the end of a shoelace to keep it from unraveling. Each time a cell divides, they become a little shorter. This makes telomeres something of a longevity marker. People with long tips at the end of their DNA strands tend to live longer than people who have short tips.  It doesn’t matter how long your shoelace is; what counts is the integrity of the cap.

In the UCI study, researchers recruited volunteers in their twenties. Some were selected because their mothers experienced a horrid event during pregnancy.  The scientists weren’t looking for the normal pregnancy stressors — work-life balance, weight gain, fretting about the baby’s health, and so on. They meant extreme stressors: a sudden divorce, a death in the family, a natural disaster, and physical or emotional abuse.

What they found is disturbing.

Compared to the control group (whose moms had a relatively stress-free pregnancy), people exposed to their moms’ extreme prenatal stress had significantly shorter telomeres.  By our mid-twenties, most of us lose about 60 base pairs of telomere length annually.  Not so of people who were exposed to extreme prenatal stress — they lose drastically more telomere length each year. The men had 178 fewer base pairs on average (equivalent to 3.5 additional years of aging).  Women had a shocking 295 base-pair deficit  (5 years of accelerated aging). It seems that a mother’s prenatal stress hits her daughter harder than her son.

How does this happen?  During pregnancy, stress may alter blood flow, oxygen, and glucose metabolism between mother and baby. High levels of the stress hormone cortisol from the mother flood the placental barrier. Excess cortisol may also slow down in the production of telomerase, an enzyme that acts as a repair kit for telomeres. Telomerase adds telomeric DNA to shortened telomeres. It regenerates our cells and tissues.  Like a fountain of youth, telomerase gives back what time takes away.

So what if you’re on a telomerase-less trajectory?

Here’s the big relief:  Your clock doesn’t have to keep ticking so quickly, even if it has been set that way before birth. There’s strong evidence that lifestyle changes can amp up telomerase production. One study found that stress management, counseling, and a healthy diet are associated with higher telomerase activity.  Another found that meditation turns up the telomerase dial.  

In the research community there’s much interest in the idea that, by maintaining our telomeres, gene therapy might someday reverse or prevent aging if started early enough.  Is it possible? As a measure to conceal the abuses of youth, teens could freebase on telomerase. 

Oh, the ways to stress out Mom.

 

 *If you like this blog, click here for previous posts and here to read a description of my most recent book, Do Gentlemen Really Prefer Blondes?, on the science behind love, sex, and attraction. If you wish, check out my forthcoming book, Do Chocolate Lovers Have Sweeter Babies?: The Surprising Science of Pregnancy. 

 

Assorted Trifles (from the science of love, sex, and babies)

Posted in news, parenting, pregnancy, psychology, science, sex by jenapincott on August 4, 2011

Research is like a box of chocolates; you never know what you’re going to find. An assortment of studies on love, sex, and babies — fresh from the lab.

Scientists found that men whose ring fingers are longer than their index fingers are likelier to have longer-than-average penises, at least among Korean men whose flaccid genitals were stretched under anesthesia. Studying the files of women who were raped in 1999-2006, French researchers discovered that there were fewer incidences of living sperm than in rape victims in previous generations, which supports the theory that sperm quality is declining. Women are likelier to get pregnant if they ovulate from their right-side ovary, visible by ultrasound, especially after two consecutive left-side cycles, inspiring women undergoing fertility treatment to desire a L-L-R pattern. Among women whose fetuses inexplicably died in third trimester, 64 percent (392/614) had a premonition before their doctors told them. They described a feeling of discomfort, of a strange unease; that they understood subconsciously that the baby would die. Many described how they dreamed of dead relatives and of death on the night the baby probably died. A recent fMRI study reported that women who had given birth vaginally exhibited greater activation in brain regions involved in the regulation of empathy, arousal, motivation and reward circuits in response to their baby’s cries compared to those who had not. Women who snore loudly and frequently were at high risk for low birth weight (relative risk = 2.6 [95% confidence interval = 1.2-5.4]), and fetal-growth-restricted neonates. The success of an IVF transfer may in part be predicted by how much glucose medium an embryo “eats” on days 4 and 5. On Day 4, female embryos consume significantly more sugar than males.

Publishers Weekly — First Review for Chocolate Lovers!

Posted in book reviews, magazine articles, media, news, parenting, pregnancy, science, sex by jenapincott on August 4, 2011

My first review for Do Chocolate Lovers Have Sweeter Babies?, from this week’s Publishers Weekly.

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Do Chocolate Lovers Have Sweeter Babies: Exploring the Surprising Science of Pregnancy
Jena Pincott. Free Press, $15 trade paper (256p) ISBN 978-1-4391-8334-2
Science writer Pincott (Do Gentlemen Really Prefer Blondes?) began her research when she was pregnant; her daughter was born during the writing process, and she describes the work as “curiosity -driven,” urging readers to flip to the pages that interest them most. As Pincott negotiates her pregnancy, she explores a wide array of subjects expectant parents will find utterly captivating, drawing from studies in evolutionary psychology, biology, social science, neuroscience, reproductive genetics, endocrinology, and largely from research in the field of epigenetics, the influence of environment on the behavior of genes. She examines each phase of her own pregnancy, addressing odor and taste aversions (the “gag list”), vivid dreams, how diet affects a gene’s behavior, and a wealth of other subjects. She delves into how dads react to pregnancy (many put on weight) and makes the remarkable observation that what grandma ate when pregnant way back when may influence the baby’s future health (“I’m eating for two generations,” she quips). While readers will be entertained and fascinated by this text from start to finish, the concluding chapter, “Lessons from the Lab,” offers expectant mothers a valuable summary of practical research-based tips (moderate stress experienced by mom may actually be good for the fetus; eating a chocolate bar a day may improve baby’s temperament). Pincott writes with humor and vibrancy, bringing science to life.

WAAROM VROUWEN CHOCOLA LEKKERDER VINDEN DAN SEKS

Posted in psychology, science, sex by jenapincott on July 4, 2011

The new Dutch mass market edition of Blondes (retitled, in loose translation, “Why Women Prefer Chocolate to Sex”)

Are Men Likelier to Cheat When Their Partners are Pregnant?

Posted in parenting, pregnancy, psychology, science, sex by jenapincott on June 13, 2011

It’s bad enough that  Congressman Anthony Weiner had been taking photos of his naked self and sending them to women who weren’t his wife.  It’s worse when we learn that his wife is three months pregnant.

Aha, that it!, some cynics claim.  Now that Weiner’s oats are sowed, he’s exploring new (and, if the twittering teen rumor is real, very green) pastures.  It’s only natural.

But is it?  Are men really more likely to cheat when their wives are pregnant?

Turns out, the answer is that it depends on the man.

Reviewing the studies of pregnancy and sex, it seems there are three categories of expectant fathers. 

  • Type Z cheats or wants to cheat (the Weiners). 
  • Type Y desires his pregnant wife more than ever.
  • And then there’s Type X  — a man who has a decreased sex drive and a lower risk of cheating on his wife.

The bad news is that at least one study found that, yes, the risk of a given man to cheat on his wife increases during pregnancy, even if he is otherwise satisfied in his marriage.  His reasons? He may feel ambivalent about the pregnancy or the changes that go with it. His partner, especially in her first and third trimesters, may not feel like having sex.  Her sex drive may diminish. She may think her body is unattractive.

(Incidentally, bodily dissatisfaction happens to be the number one reason why most women have less sex during pregnancy.  Most of us think pregnancy is a turn-off for men.  That’s a misconception.)

But here’s the good news for pregnant women.  Fact is, many men — the majority as found in this study — desire their pregnant partner even more over the course of the pregnancy, even if they aren’t having as much sex as before. They find her as physically attractive as she was prepregnancy, if not more so. These are usually the Type Y guys. Another study found that, while couples had sex less frequently in third trimester, the only circumstances under which men change their sexual behavior is if they are older or worried about the safety of the fetus. (Note:  Sex does not raise the risk of miscarriage in pregnancies that are not high risk.) Otherwise, men desire sex with their wives just as much.

From an evolutionary perspective,this makes some sense.  Women benefited from having their mates around to help support them through pregnancy and childrearing. Sex helps men stick around.

The Type X expectant father – the one with a low sex drive and a lower risk of infidelity – may overlap with Type Ys. These are men who, at some point over the nine months, are afflicted with pregnancy symptoms:  nausea, weight gain, mood swings, fatigue, even vomiting. Hormones are the culprit.  These men have higher levels of prolactin, a hormone associated with sluggishness, weight gain, and bonding and parental behaviors.  Their testosterone levels plummet, making them less combative and sexually aggressive.

There’s an upside to Type Xs. It turns out that these faithful, fattening men display the most fatherly behavior when the baby arrives.  As new dads, they’re more likely to hear and respond to their infant’s cries.  They’re more compassionate and tolerant.  They make better fathers.

One might speculate that Weiner’s Type-Z behavior while his wife is pregnant doesn’t bode well for Weiner’s fathering instincts. It’s clear that if any hormone is raging in the man, it’s testosterone — not prolactin. He is probably not sharing his wife’s morning sickness and taking turns with her over the toilet.

There’s no crime in what Weiner has done; he’s just another politician more interested in power more than paternity.  But he is making us a little nauseous.

 *If you like this blog, click here for previous posts and here to read a description of my most recent book, Do Gentlemen Really Prefer Blondes?, on the science behind love, sex, and attraction. If you wish, check out my forthcoming book, Do Chocolate Lovers Have Sweeter Babies: Exploring the Surprising Science of Pregnancy. 

 

How big is your limbal ring?

Posted in news, psychology, science, sex by jenapincott on April 30, 2011

Of all the qualities that give an attractive person an edge, here’s one you’ve likely overseen:  the limbal ring,  the dark circle around iris.  The limbal ring is the line that separates the colored part of the eye from the white (the sclera).   

It’s completely unconscious, the way we all judge others’ limbal rings. In the 20 milliseconds or so it takes to assess a person’s attractiveness, you’re factoring in the size and shade of the limbal rings. The bigger and blacker they are, the more attractive the eyes. People with the prettiest eyes have the most prominent limbal rings.  

This, anyhow, is the upshot of a recent study by Darren Peshek and his colleagues at the Department of Cognitive Science at the University of California at Irvine. The researchers showed volunteers eighty pairs of male and female faces.  Each pair of faces was identical except the eyes: one had dark limbal rings and the other had no limbal rings.  The volunteers were asked to pick which face was more attractive and to indicate their degree of preference.

Men thought women with the dark limbal rings were more attractive than those without, and women thought the same of men with dark limbal rings.  Men and women also judged faces of the same sex as more attractive when the limbal rings were large.

Looking into my baby daughter’s eyes, I see the blue of her iris is framed by a thick black limbal ring.  The contrast makes the white of her eyes so white they look blue. The very young have the thickest, darkest limbal rings.

Which is exactly the point.  The limbal ring serves as an honest signal of youth and health-desirable qualities, reproductively speaking. The ring fades with age and with medical problems.  It’s thickest from infancy through the early twenties.  A thick, dark limbal ring may make us appear younger.  It makes the whites of the eyes whiter.  This might be why so many people think light eyes are so sexy:  the limbal ring, when present, shows up more.  

There are so many ways to fake the appearance of youth. You can wear makeup and wigs and get tummy tucks, plastic surgery, Botox, and boob jobs.

But a fake limbal ring?

Yes, this too. Long ago, Japanese schoolgirls discovered the edge a limbal ring can give you by wearing “limbal ring” contact lenses. They make the eye look bigger and more defined. And while you’re eyeing these contacts, you might as well buy a set that expands your pupils too. Big, dark, dilated pupils signal emotional arousal. They, too, act on the unconscious favorably.

The limbal ring is well-named. Limbis means border or edge, and it’s related to limbic, meaning emotion or drives. The limbal ring, seen from inches away, is an intimacy zone. Don’t flirt until you see the whites of their eyes.

Why are Men Mad About Mammaries?

Posted in news, psychology, science, sex by jenapincott on April 3, 2011

Why do men love breasts?

Let me count the theories:

1. Freudian (breasts remind men of their moms and the nurturing of childhood)
2. Evolutionary (breasts resemble buttocks, and prehuman ancestors always mounted from behind)
3. Reproductive (breasts are an indicator of age, and big breasts in particular are a marker of high estrogen levels, associated with fertility).

Do these reasons sufficiently explain why breasts are beloved — even in cultures that don’t eroticize them any more than the face?

If not, here’s another:

Breasts facilitate “pair-bonding” between couples. Men evolved to love breasts because women are likelier to have sex with — and/or become attached to — lovers who handle their breasts.

This idea came up in New York Times journalist John Tierney’s interview with Larry Young, a neuroscientist famous for his research on monogamy. According to Young, “[M]ore attention to breasts could help build long-term bonds through a ‘cocktail of ancient neuropeptides,’ like the oxytocin released during foreplay or orgasm.”

The same oxytocin circuit, he notes, is activated when a woman nurses her infant.

When women’s breasts are suckled, as they are during breastfeeding, the hormone oxytocin is released. Oxytocin makes the mother feel good and helps her bond with her baby. She feels loving and attached. The same reaction might happen if a man sucks and caresses a woman’s breasts during foreplay. In our ancestral past, the most titillated men may have been the ones to attract and retain mates and pass on their genes.

The “boobs-help-bonding” theory may not be the strongest explanation of why men love breasts, but it’s worth introducing to the debate. That said, there are many ladies out there for whom a lover’s suckling does nothing — and there are many breast-ogling boobs who know nothing of foreplay.

Do baby tears have mind-control properties?

Posted in news, psychology, science, sex by jenapincott on March 8, 2011

A few weeks ago, Israeli neuroscientists Shani Gelstein and Noam Sobel published a study about mind-control properties in human tears. The gist of the research, which enjoyed much media attention, is that women’s tears contain a chemical signal that reduces sexual desire in men. Tears were collected from the cheeks of emotionally-distraught women watching sad films and wiped on the upper lips of male volunteers. Compared to men who whiffed a salt solution control, the tear-sniffers not only had a reduced sex drive but also lower testosterone levels and reduced brain activity.

A leading explanation is that chemicals in tears generally reduce male aggression, making them more sympathetic.

How does this work? One theory is that one or more of the hundreds of chemicals in tears has “mind-control” properties, triggering specific predictable behaviors in others. (Here and here I write about how this happens in sweat, too.) One candidate is prolactin, a hormone associated with bonding. When inhaled in a person’s tears, prolactin may affect the sniffer’s hypothalamus, the part of the brain that produces hormones which in turn affect behavior.

Baby tears have not been the subject of a study yet (hopefully soon). But it’s not a far cry from certain that if there are chemicals in the tears of women that affect men, there are also chemical triggers in the tears of babies that affect their caregivers or anyone else that comes into contact with them. These tears may trigger care-giving instincts and reduce aggression toward the screaming infant.

I wonder: Infant abuse is relatively uncommon given how irritating a screaming baby can be. Are the people guilty of this crime more likely to be amnosiacs (loss of smell-sense) or have another form of brain damage that would prevent them from inhaling aggression-reducing signals in the baby’s tears?

Another theory: Kids cry all the time and sometimes it’s hard to tell when they really need attention. Might chemicals in emotional tears direct parents to respond appropriately when there is a real need for attention? Assume these chemical signals are only in emotional tears–not crocodile tears or sleepy-time tears. Do they help us intuitively know when it’s OK to let a child cry it out instead of rushing to soothe her?

What your date’s fingerprints reveal

Posted in news, psychology, science, sex by jenapincott on February 6, 2011

Not long ago, people everywhere started to do the “finger game” on a first date. This is not as naughty as it sounds. As I describe in BLONDES, the finger game involves asking your companion for a look at his (or her) right hand. If his ring finger is longer than his index finger it’s a sign of prenatal exposure to high levels of testosterone. People with longer ring (than index) fingers are likelier to be more aggressive, better at sports, and more musically inclined. They may have more sex partners in life.

Now you can take the game to the next level: fingerprints.

Take a close look at the ridges on your companion’s fingers. (Actually, they’re best seen under a magnifying lens or photocopied and enlarged.) Most people have slightly more ridges on the fingers of one hand than the other.

More ridges on the right-hand fingers: This indicates higher levels of prenatal testosterone. He or she might master mental rotation – knowing which one of four abstract figures, revolved in three-dimensional mindspace, matches a diagram (a “masculine” task). Right-ridge dominant people are also better at aiming at a target and getting a bull’s eye.

More ridges on the left-hand fingers:
This indicates lower levels of prenatal exposure. He or she may be a whiz at games like word associations, taking a word like clear and coming up with glass then Philip then opera then ghost, or naming as many round objects as she can in three minutes (considered “feminine” tasks). Compared to straight men, gay men have more ridges on their left pinkies and thumbs.

Four or more ridges on the fingers of one hand than the other: This reflects how much stress your companion weathered when he or she was a second-trimester fetus. For instance, researchers found that women who were 14-22 weeks pregnant when an epic ice storm hit Canada were more likely to have babies whose ridge counts varied greatly between hands. In nature, dramatic asymmetry is often a sign that the fetus has been stressed in some way. The more stress, the less symmetry. In fact, those with significantly asymmetric ridge counts between right and left hands were more likely to score lower in language and intellectual development as toddlers. Both fingerprint development and the brain may have been affected by constriction of blood flow to the placenta or stress hormone levels.

Other ridge count studies have also found interesting correlations: a significant difference between the ring and pinky fingers of the right hand is associated with less muscle mass in the lower extremities and a bulked-up upper body, including a thicker waist. A difference of around three or four more ridges between the thumb and pinky fingers is also associated with diabetes later in life. Asymmetries are also connected to cleft lip, dyslexia, schizophrenia, infections, and other prenatal problems.

Around ten weeks after conception is when the bottom (basal) layer of fetal skin outgrows the top (epidermis), and the tension between the two causes the skin to buckle. At this time fingerprints are like wet cement: any disturbance until mid- pregnancy may leave a lifelong impression. At this time the skin and the brain are both are made of the same raw material — fetal ectodermal tissue. Any disruptive event in the womb left its mark on both. This means that fingerprints give us clues about the brain.

You would like to know more about the minds of the people you date, which is why you’re analyzing their fingers. Of course if you could read their minds, you’d know they think you’re crazy.

Do you carry DNA of former lovers in your body?

Posted in pregnancy, psychology, science, sex by jenapincott on January 28, 2011

This bit of science arcanum is especially cringe-worthy.

Many years ago, scientists first discovered that a large minority of women have Y-chromosome gene sequences in their blood. At first glance, this seems strange. Men are born with Y-chromosomes but most women are not. The male cells in these women must’ve come from somewhere else.

But where?

The most obvious source is a fetus. Nearly every woman who has ever been pregnant or had a baby has cells from her fetus circulating in her bloodstream. These cells filter through the placenta and reside in the mother’s bloodstream and/or organs — including her heart and brain — for the rest of her life. This condition is called microchimerism, named after the Greek chimera, a creature composed of the parts of multiple animals. Pregnancy-related microchimerism explains why women with sons would have Y-chromosome sequences in their blood.

This is fascinating enough. But how do you explain why women without sons also have male cells circulating in their bloodstream?

This was the subject of a study by immunologists at the Fred Hutchinson Cancer Center. They took blood samples from 120 women without sons and found that 21 percent of them had male DNA. Women were then categorized into four groups according to pregnancy history: women with daughters only, spontaneous abortions, induced abortions, and no children/no abortions.

While the number of women bearing male DNA was highest in the groups that had abortions (nearly 80 percent), women who had only girls or no babies (20 percent) also had male cells in their blood. For no apparent reason.

There are other reasons why women in the fourth group carried male cells: inherited in the womb from a male twin that passed, from a miscarriage they did not know about, from their mother via an older brother…

Or through sexual intercourse.

There remains a possibility, however remote, that cells from a lover may pass be transmitted during sex. Those cells may hang out forever in the recipient’s body, taking residence in any organ. These cells are the imprint of lovers past, a trace of living history.

Might a woman’s bodily fluids enter a cut in a man’s genitals as well? Could men carry around the genes of women they’ve slept with?

The imagination is stirred. What are those foreign cells doing in hearts and minds? Are they wreaking havoc in our heads? Do the cells of former lovers clash? In a science fiction scenario a person could even take a drop of her own blood, isolate a cell from her former boyfriend, and clone him. Then do with him what she will.

The upshot of this research? It’s yet another reason to use a condom.

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