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. 

 

 

 

Advertisements

A Kirkus Star!

Posted in book reviews, parenting, pregnancy, science by jenapincott on September 8, 2011

Absolutely delighted that Kirkus gave “Do Chocolate Lovers Have Sweeter Babies?” a starred review. Thank you, Kirkus!
—-

Popular-science writer Pincott (Do Gentlemen Really Prefer Blondes?, 2008, etc.) provides a lively, accessible romp through the science of pregnancy.

Known for her previous research on love and sexual attraction, the author makes a natural transition in her latest. Delving into the science of pregnancy, parenthood and fetal development, she presents her findings with wit, personal anecdotes and playful humor. Eschewing predictable “avoid the shellfish” advice, Pincott provides a science-based trivia collection, drawing from studies in evolutionary psychology, biology, neuroscience, social science, epigenetics and more. She explores topics such as how a woman’s activities might influence her unborn baby’s personality, how pregnancy and motherhood can change the behavior of mothers and fathers, what factors might influence a baby’s gender and why the first hour after a baby’s birth means so much for mother-newborn bonding. Inspired by questions from her own first pregnancy, the author also digs up the answers to common inquiries such as “what does baby’s birth season predict?”; “what can Mozart really do?”; and “will what we eat now influence baby’s tastes later?” Despite the bombardment of information, Pincott presents her research as fun things to contemplate rather than additional things to worry about, so nervous expectant parents can thoroughly enjoy the book.

A fascinating supplement to the typical maternity guide.

IQ and Fish, the Whole Fish, and Nothing But the Fish

Posted in news, parenting, pregnancy, psychology, science, Sweeter Babies by jenapincott on August 30, 2011

For the nine-plus months of pregnancy, I dutifully downed fish oil pills. I had heard all about the virtues of essential fatty acids (especially DHA, docosahexaenoic acid), known collectively as omega-3s, which are found in fish such as salmon and sardines. These fats are involved in the development of new neurons and help form the cell walls — the structural support — of nerve cells. If the healthy brain is like a sponge, then the brain deprived of omega-3 is like a puddle.

Several years ago, in 2007, an enormous study funded by the National Institute of Health looked at the link between children’s scores on aptitude tests (at ages 6 months to 8 years) and their mother’s prenatal consumption of fish. It turned out that the kids whose moms ate fish more than twice weekly during pregnancy were significantly less likely to have low scores on cognitive tests. Low maternal seafood intake (two or fewer servings weekly) was also associated with increased risk of suboptimum outcomes for prosocial behavior, fine motor, communication, and social development scores. This was a huge deal. The nearly 12,000 expectant women who participated in the study were asked to record how much whole fish they ate, not fish oil supplements.

Naturally, this study — and smaller studies like it involving whole-fish consumption — inspired millions of pregnant women to focus on fish oil.

Problem is, not many of us want to or can afford to eat fish every day. Fears of mercury and PCB contamination are valid (many varieties of fish, such as tuna, have high levels that are toxic to fetuses). It’s not much of a stretch to say that fish oil pills are a better way to get your daily DHA.

But here’s the interesting part. Everyone has assumed that when it comes to omega-3 fatty acids like DHA, the source — whole fish or fish oil pills –shouldn’t matter.  Seems reasonable, but is it?

A few very recent fish oil studies cast doubt:

Results of fish oil pill supplementation range from neutral to negative…

A review of six clinical trials (1280 women in total) involving fish oil pill supplementation during breastfeeding found no significant difference in children’s neurodevelopment: language development (intelligence or problem-solving ability, psychomotor development, motor development. In child attention there was a significant difference. For child visual acuity there was no significant difference.  For language development at 12 to 24 months and at five years in child attention, weak evidence was found (one study) favouring the supplementation.

• At the Women’s and Children’s Hospital in Adelaide, Australia, researchers tracked the children of 2400 women who took DHA-rich fish oil pills in the last trimester of pregnancy. The use of these fish oil capsules compared with vegetable oil cap- sules during pregnancy did not result in improved cognitive and language development in their offspring during early childhood.

Other fish oil pill studies found disturbingly negative results:

• At the Universities of Copenhagen and Chapel Hill, researchers followed 120 Danish women who nursed their babies for four months after birth and took fish oil supplements (or olive oil pills). The children were tested in intervals up to seven years. The higher the early intake, the lower the child scored in speed of information processing, inhibitory control, and working memory tests. Boys whose mothers consumed fish oil had lower prosocial scores relative to the olive oil group.

Meanwhile, these recent studies strengthened the evidence that eating fish is brain-boosting:

• In a study that took place the Arctic, 154 11-year-old Inuit children took standardized tests for memory and verbal learning. Their scores were compared with their levels of DHA present in their cord blood at birth. Children who had higher cord plasma concentrations of DHA at birth achieved significantly higher scores on tests related to recognition memory processing. The source of DH in their mothers’ diets was fish and marine mammals. Intriguingly, the connection with higher test scores remained intact regardless of seafood-contaminant (PCB and mercury) amounts.

* A UK study of 217 nine-year-olds whose mothers had eaten oily fish in early pregnancy had a reduced risk of hyperactivity and children whose mothers had eaten fish (whether oily or non-oily) in late pregnancy had a verbal IQ that was 7.55 points higher than those whose mothers did not eat fish.

This is what I’d love to see: large studies that compare pregnant/nursing fish-eaters versus pill-poppers. Few researchers have tackled this, in part because we assume DHA works the same no matter how we get it, and because DHA from sources other than pills is difficult to measure or isolate.  Interestingly,  a study at the Norwegian Institute of Public Health compared height, weight and head circumference results of newborns whose mothers whose main source of DHA was fish versus pills.  They found that fish-eaters generally gave birth to larger babies while fish-oil-pill-poppers had newborns with a smaller head circumference.

Is it possible that fish consumption boosts IQ, but fish oil pills do not?

It’s dumbfounding, the difference in results between whole fish and fish oil. The researchers that found negative results of supplementation on nursing infants speculated on what goes wrong. It may be that early intervention with fish oil pills results in an “environmental mismatch” between prenatal and postnatal life,” (e.g. the fetus is “programmed” in the womb to live in an environment without abundant DHA and is thrown off when inundated with these fats later on).

Another theory is that the timing in these recent fish oil pill studies is off. The critical period in which fish oil may influence brain growth may be in the first trimester of pregnancy or toward the end of the first year of life — not during the time periods in which women in these studies were taking fish oil pills. It may be that DHA has a “sweet spot” — an optimum level below and above which may be detrimental to the developing brain. Indeed, when researchers look at fish oil pill supplementation and DHA-deficient premature infants, the results are much rosier.

There’s another compelling explanation of why fish oil pills don’t yield the desired results: DHA doesn’t do its magic alone. Nutrients and proteins in fish and seafood, other than DHA, may be  brain-boosters — or at least help us (and our fetuses or babies) to absorb or metabolize DHA better. All the fish oil in the sea can’t compensate for a bad diet.

In the US, a federal advisory recommends that pregnant women not eat more than two servings of fish weekly. This advice may be misguided given that fish such as salmon and sardines are high in DHA but low in mercury. Pop fish oil pills instead; they’re just as good– that’s been the message. But these recent studies point to a different truth.

Thus the case for fish, the whole fish, and nothing but the fish.

Food for thought.

*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. 

 

Do Beautiful Babies Become the Most Beautiful Adults?

Posted in pregnancy, psychology, science by jenapincott on August 18, 2011

The Gerber baby, then and now

Forgive me, I believe my one-year-old is the cutest baby ever. Yes, yes, mothers are biased about their own children.  As I detail in my new book, certain reward circuits “light up” in parental brains only when looking at their own offspring.  But objectively — objectively! — my daughter is adorable.

The little one has “Gerber baby” features:  a bulbous forehead, big eyes, luscious cheeks and thighs (and curls). Babies with these qualities are rated as cuter than those with sunken foreheads, small eyes, and large or long chins.  Adults smile and gaze longer at them. Attractive infants are perceived to be more sociable, easier to care for, and more competent than their homely peers. They inhibit aggression in adult men. They receive more nurture.

Our baby thrills to the attention, and my husband and I have started to worry that being cute might not lead to anything good.  I have a theory that ugly ducklings and tomboys grow up to have richer inner lives.  I don’t want a princess.

We want to know:  Do the cutest babies turn out to be the most attractive adults?

Conveniently, a recent study by psychologists Gordon Gallup Jr, Marissa Hamilton, and their colleagues addresses this very question. (I love these whimsical studies; they’re motivated by genuine curiosity.) The presumption is that physical attractiveness remains stable over time.  This has been proven in childhood onward:  attractive ten-year-olds are likelier to be attractive adults.  (Another study found that adult attractiveness can be predicted as early as age five).  But until now no study had tracked attractiveness from infancy.

It’s interesting, how the psychologists went about it.   They sifted through high school yearbooks and found forty graduating seniors who featured photos of themselves as infants. Then they asked several hundred college students to rate the the individuals — in infancy and in adulthood — for attractiveness.

The upshot?

There was no correlation between attractiveness in infancy and (young) adulthood. Some ugly ducklings turned into swans, some baby swans become ugly ducks.  Some gawky, awkward babies remained that way into their senior year of high school.  And some beautiful babies kept their glow through the years. This was true of males and females alike.  Cuteness — or homeliness — in infancy does not predict future attractiveness.

The study included an interesting side finding:  While the raters were likely to agree about which infants were attractive, they often disagreed about which eighteen-year-olds made the cut. Why? The gold standard of baby beauty — the forehead, the eyes, the thighs — is universal. These preferences are hard-wired in us to elicit care and protection, while the perception of adult beauty is tempered by culture.

Cute babies are universal positives.  In this light, it’s OK that mine gets attention now.  The future will be much less predictable.

 

 *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. 

 

Do Flame Retardants Make Us Dimmer?

Posted in parenting, pregnancy, psychology, science by jenapincott on July 6, 2011

When I was in the second trimester of pregnancy, my husband and I bought a new king-sized mattress.  Like all cotton mattresses sold in the U.S., ours had been treated with a flame retardant containing polybrominated diphenyl ethers (PBDEs) and/or organohalogen compounds (OHCs). Flame retardants are also in pillows, car and airplane seats, drapes, rugs, and insulation. They’re in electronic equipment, like TVs, and in the dust on top of TVs.  They’re in air and soil and breast milk.  Almost all humans have flame retardants flowing through their veins.

             Around the same time I got my new mattress (on which I tossed and turned in third trimester), two surprising studies were published on the effects of flame retardants on fetuses and young children.

Study #1

A group of researchers at the University of Gronigden in the Netherlands recruited nearly 70 pregnant women in third trimester, taking samples of their blood and measuring it for PBDEs and OHCs. Five years later, the children were given standardized developmental tests for motor skills (balance and coordination), cognition (intelligence, spatial skills, control, verbal memory, and attention), and behavior.

The result:  PBDEs were correlated with worse performance on fine motor tasks and a shortened attention span.  Strikingly, they were also linked with better coordination and visual perception, as well as better (more placid?) behavior.  OHCs, meanwhile, were correlated with worse fine motor skills. Oddly, these kids had better visual perception.

 Study #2

 Researchers at Columbia University tested for PBDEs in the cord blood of nearly 400 women who delivered their babies at a New York City hospital.  These children were given mental and motor development tests in infancy and, later, at four-to-six years. These tests measure memory, problem solving, habituation, language, mathematical concept formation, and object constancy.  They also assess ability to manipulate hands and fingers and control and coordinate their movements.

 The result:  At both age intervals, children who had higher cord blood concentrations of PBDEs scored significantly lower on tests of mental (lower IQ) and motor development.  This was particularly evident at age two for motor skills and age four for IQ (nearly 8 points lower for certain PBDEs).

 

            Are flame retardants slowing us down? Correlation is not causation, but there’s a real risk that they do — and researchers have some ideas about how these chemicals have a toxic effects on the brain. OHCs (for instance) have been found to decrease a fetus’s production of thyroid hormone by interfering with thyroid receptors. This leads to an increase in thyroid stimulating hormone (TSH). Brain development in the fetus relies on the precise timing and quantity of thyroid hormone; too much or too little causes developmental delays. High prenatal exposure to TSH is associated with lower IQs – 4 points less on average.  During critical developmental periods, PBDEs and OHCs may also have a toxic effect on neurons in the hippocampus, the memory region of the brain, by reducing the number of neurotrasnmitter receptors.

            Infants and toddlers have what researchers call a high “body burden” of flame retardants. Household dust, which floor-playing infants and toddlers encounter constantly, accounts for 80-93 percent of postnatal PBDE exposure, followed by breast milk (however, the benefits of nursing appear to outweigh this drawback; breastfed babies score higher on neurodevelopmental tests). 

            A disturbing fact is that American kids have levels of PCBEs that are 10 to 1,000 times higher than their peers in Europe or Asia. We produce 1.2 billion pounds of the stuff annually. (Interestingly, the Scandivanian study, whose subjects had lower levels of prenatal exposure, found no IQ deficit while the U.S. study did.) Consider our nation’s problems:  attention deficit disorder, placidity, lower standardized test scores in reading and math.

Are flame retardants making kids dimmer?

            The question fires up the imagination.  Should pregnant women be advised to avoid, say, dusting and buying new mattresses in the same way we avoid emptying the litter box (to avoid toxoplasmosis)? Are the perceived gains in visual perception real, and, if so, why, and do they come at the expense of other abilities? Are urban kids at a higher risk  than average? Are there naturally flame-retardant materials that we can use in lieu of chemicals?   More research, especially on American kids, is warranted.

            After all, the nightmare scenarios can keep an expectant mom up all night, tossing and turning on her nonflammable mattress.

 

 * If you wish, check out my forthcoming book, Do Chocolate Lovers Have Sweeter Babies: The Surprising Science of Pregnancy. 

 

Are Extroverts That Way Because of Their Fathers?

Posted in parenting, psychology, science by jenapincott on June 24, 2011

All babies demand their parents’ attention. But how many 11-month-olds demand the attention of strangers, too? Ours does. We bring her to restaurants and she scans the room until she catches someone’s eye. My husband will pick her up and carry her over to her admirer, whom he’ll chat up. Dad’s a socialite, Baby’s a socialite. Mom reaches into her bag and pulls out a book.

You might think your baby’s social confidence depends on the usual mix of genes and environment. This is true, but it might not be the whole truth. There’s also evidence that children rely more on their father’s social signals than their mother’s. That is, socially confident dads may have more socially confident kids. Socially anxious fathers may have more socially anxious kids. It matters less whether Mom is a social butterfly or a bookworm.

The bulk of the research on paternal influence on sociability comes from Susan Bogels, a professor in Developmental Psychopathology at the University of Amsterdam, and her colleague Enrico Perotti. In a recent review, Bogels and Perotti draw on research that suggests a dominant paternal role in their children’s sociability, including:

In one study, 9-11-year-olds were asked to imagine themselves in a series of stories involving strangers, while their mother and father responded in a socially anxious or socially confident way. Children who had socially anxiety were more influenced by their father’s reaction more than their mother’s.

A study of boys with behavioral problems, including social anxiety, found that fathering, but not mothering, predicted the children’s level of inhibition. In another study, secure infant-father attachment, but not infant-mother attachment, predicted stranger sociability among toddlers.

• Among kids enrolled in treatment for social anxiety, those whose fathers had high levels of social anxiety had a worse outcome (were more socially anxious) than those whose mothers had it. Socially anxious mothers are not as likely as socially anxious fathers to make their kids less sociable.

So here’s the mystery: Why would fathers, who have less to do with childrearing than mothers, have more influence on their children’s sociabilty?

It’s an interesting question, and Bogels and Perotti have an interesting answer. “In the course of human history,” they write, “fathers specialized in external protection (e.g. confronting the external world outside the clan or extended family), while mothers provided internal protection (e.g. providing comfort and food). Therefore, children may be hardwired to respond more to their father’s signals about the social world than the mother’s, and adjust their behavior accordingly.

Through the ages, it benefited children to rely more on their father’s than mother’s cues about whether unfamiliar people are generally hostile or cooperative. Of course, gender roles have long since changed – moms go out into the world every day and meet strangers – but our instincts haven’t.

So the lesson here is that fathers orient their children outward, mothers inward. When researchers observed a group of toddlers taking swimming lessons, they took note of where the parents stood. Mothers protectively stood in front of their babies, encouraging face-to-face interaction with them. Fathers stood in back, so that their children would face their social environment.

∞∞∞∞∞∞∞∞∞∞∞∞

Bogel and Perotti’s review includes a fascinating aside about paternal roughhousing and its effect on children’s social confidence. Rough-and-tumble play – I think of my husband tossing our infant in the air, spinning her around, throwing her over his shoulder, as she giggles and squeals- gets a scientific seal of approval.

Here’s why. Kids learn to associate physiological arousal – a racing heart, tight chest, spinning head – with fun instead of fear, which crosses over into other social interaction. Roughhousing also involves behavior – being aggressive, sneaky, teasing, playful – that requires different roles and different responses, and forms a basis for social skills. By pinning kids to the ground, swinging them like sacks of potatoes, attacking them and getting attacked – fathers make their progeny more confident.

∞∞∞∞∞∞∞∞∞∞

So many questions. If we have evolved so that fathers strongly influence their children’s sociability, what does this mean?

It means that fathers who are socially anxious themselves are likelier to have kids who are not socially confident. If a kid suffers from severe social anxiety, perhaps his or her father should be involved in the kid’s therapy or get therapy himself. But what about kids who don’t have fathers who are involved or live at home? How do mothers compensate? And what about gender? So far there is no evidence that boys are more susceptible to the father’s signals than are girls, but is this really so? And what about other male figures – male teachers, older brothers, uncles, grandfathers – are they equally influential? At what age is paternal influence on sociability strongest? And are paternal genes more influential here too?

Further research is warranted. Until then, we can wonder about the great socialites in history – the Jackie Os, Andy Warhols, Paris Hiltons, Truman Capotes, Gloria Vanderbilts, Nan Kempners, and Ivana Trumps. Did they get it from their dads?

 

 

 

Where Do Demanding, Unweanable Babies Come From?

Posted in news, parenting, pregnancy, psychology, science by jenapincott on May 24, 2011

A season ago, when my daughter reached the six-month mark, her pediatrician told us to introduce her to a new food every few days and see what she likes. It wasn’t time to wean her, but soon it will be, and supplementation should help the transition. So I lovingly shopped for organic fruits and vegetables: apples, bananas, avocados, peas, and so on. I presented them passively — as items for her to experiment withon her placemat — and actively, by making mmmms, playing airplane, and swallowing the goop and showing her my tongue.

Three months later, we’ve made astonishingly little progress on the solids front. At best, the infant deigns to nibble delicately on peas and lentils. She’ll squish the bits of mango and avocado on her plate and drop them on the floor. She’ll taste a food then whip her head to the other side and bat away the spoon. She wrinkles her nose.

All she really wants to do is nurse. Baby loves to nurse. She cries and cries in the wee hours of the morning because she wants to nurse. She is tall and heavy for her age.

Who’s to blame (at least in part) for her unweanable stubbornness?

Her dad. 

It’s not only convenient to blame the father for babies who won’t give up nursing, It’s scientific.  There’s evidence.    

Here’s how it works, according to a new study Bernard Crespi, an evolutionary biologist at Simon Fraser University.  How much and how long a baby nurses depends in part on her genes. The genes she inherits from her father have an ulterior motive.  Paternal genes want the baby to extract as much as possible from the mother.

Paternal genes are thought to influence:

  • suckling strength  (so the baby extracts as much milk as she can)
  • tongue size (a larger tongue is a better suction pump)
  • crying  (for maternal attention and food)
  • appetite and speed of eating
  • duration of breastfeeding before weaning
  • night-time suckling (results in suppression of periods, which helps delay future pregnancies/siblings)

The genes that influence these behaviors are active only when they come from the dad. This is called genetic imprinting — when only the genes from one parent are expressed. Dad’s genes strongly affect the intensity of infant behavior.  Only a tiny percentage of human genes are imprinted. 

Dad’s genes are greedy for a good reason. From a biological perspective he has nothing to lose by making sure this particular offspring who carries his genes demands a lot of her mom — including suckling often, crying a lot, and taking a long time to wean. This behavior may be essential to a child’s survival in a setting in which resources are limited. “Weaning” genes have been shaped this way under evolutionary pressure in a premonogamous era.

Mom’s genes, meanwhile, are more moderate.  They want the child to survive but dial back the feed controls. They’d prefer for a baby to self-feed and start solids sooner. Mom’s genes push moderation to save resources (time and energy) for her other (or future) offspring. When paternal genes are disabled and maternal genes are active, babies have Prader-Willi syndrome, a condition that manifests as inability to latch and suckle effectively, complacency, and lack of crying or other solicitation for food.  These infants wean early because they never really nurse. They fail to thrive.

Demanding, unweanable infants come from dads. At a minimum, paternal genes play a real role in their aggressive eating, crying, and nursing behaviors.  

Now that they’re outed, perhaps guilty fathers should be the ones to work the night shift and scrape  food off the floor?

Do Brothers Stall Their Sisters’ Sex Lives?

Posted in parenting, psychology, science by jenapincott on March 20, 2011

Nearly eight months ago I gave birth to a baby girl. The child is now a seam-popping twenty-plus pounds. Infants, they grow so quickly it’s creepy — my thoughts fast-forward through her teething years to the teens, and I’m terrified. Problem is, my family lives in New York City where children want to be adults. The weenies of tweens should stay in their jeans, but all too often they don’t.

The onset of girls’ sexual maturity depends a lot on the social environment — peers, culture, and so on. A recent study by Australian behavioral ecologists Fritha Milne and Debra Judge found that it especially depends on the family environment, and not in the expected ways of curfews and chastity pledges. Sure, if you’re a teenage girl your parents might hold you back from trying to lose your virginity. So may your grandparents and any other authority figure in your family.

But so might your little brother.

Milne and Judge recruited nearly two hundred women and seventy-six men, all living in or around the city of Perth, Australia, and asked them questions about their family lives and sexual development. The results were that girls with only younger brothers lost their virginity an average of more than a year later (at age 18.3) than girls with younger sisters only. Girls with both younger brothers and sisters lost it nearly two years later on average (age 19.3) than girls with no younger siblings. Younger sisters alone had no impact.

The chastity effect only applied to girls with younger brothers. Having a big brother (or sister) didn’t make a girl any less likely to hold onto her virginity, yet another strange pattern emerged. This one involved the girls’ physical maturity.

The more older brothers a girl had, the later she got her first period. Girls with only elder brothers got their first visit from “Aunt Flo” up to a year later (at age 13.6) than girls with older sisters or no older siblings (age 12.7). (This is meaningful given that breast cancer and other conditions are related to earlier menstruation.)

Elder brothers delay physiological maturation, while younger brothers delay behavioral maturation.

What’s going on?

Trained as behavioral ecologists, Milne and Judge took a look at the big picture. Daughters are often caregivers. Historically, as has been found in traditional societies, a woman with daughters as first- or second-born children has a larger family than a mom whose first children were sons. Elder daughters take care of younger siblings, which frees up Mom to keep popping them out. Boys historically required more resources than do girls, which made big sister’s contributions even more important. As a result, these helpful elder daughters experience a delay in starting their own families. In the modern world where women don’t usually start their families until their mid-twenties on average, this is no problem, but in the past females with brothers may have had fewer children over their lifetimes.

The bigger mystery is what’s actually behind Big- and Little Brother’s stalling effect on their sisters’ sexuality. This is unknown territory, so Milne and Judge tread lightly here. The safest theory is that the delays are behavioral. Girls with little brothers lose their virginity later because they’re too busy taking care of their siblings to have love lives of their own. Perhaps little brothers, who are slower than female siblings to develop and reach puberty, keep their elder sisters in a more childish mindset. Or perhaps the stress of care-giving slows down puberty.

The researchers should also consider a much more surprising yet equally plausible theory: brothers send out chemical cues (pheromones) in their sweat that inhibit their sisters’ sexual development. Odd as it sounds, this would explain the perplexing finding that girls with older brothers get their first periods later than their peers. And, it appears, so do girls who grow up with their biological fathers in the household, compared to their peers with absent dads. Several studies, including here and here and a large one at Penn State that involved over nineteen hundred college students, came to this conclusion. (Interestingly, the same study found that girls growing up in homes with males unrelated to them got their periods earlier than average.)

The sweat-stifles-sexuality theory isn’t as far-fetched as it sounds. Other animals — rodents, for instance — use pheromones to modulate sexual maturity and fertility in a population. Over the years, a girl would inhale chemical cues in fraternal sweat — think of all those sock and armpit odors. Those chemicals would hit the hypothalamus of her brain where sex hormones are produced, and slow down the works. Puberty strikes a little later. Evolutionarily speaking, the result is that a girl could stay in the family nest longer without conflict. The risk of incest is reduced.

So should I try for son now? Truth is, the data applies to populations, not individuals. There are no guarantees; these are just interesting findings that deserve more research. Moreover, I’m in over my head right now with my baby girl’s teething and feeding challenges. Sure, I’ll want preserve her girlhood for longer than a New York minute. But I also need to preserve my sanity

 

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?

Would you eat your baby’s placenta?

Posted in news, polls, Polls and Surveys, pregnancy, science by jenapincott on November 14, 2010

“You’ve never seen a mother cat with postpartum depression, right?” a woman in my prenatal yoga class asked me. She had a challenging look in her eyes. Before I could respond she rushed to her punchline. “It’s because cats eat their placentas.”

The woman introduced herself as a doula-in-training who prepares placenta on the side. She thought I might be interested.

I learned that placentophagy, the act of eating the afterbirth, is common among other mammals. Animals probably eat it for the extra iron and other nutrients, to detract predators, or possibly to alleviate pain (not to thwart the kitty blues). My fellow yogi is among the small but passionate population of birthing specialists who believe that women should eat their placentas, too — especially to ward off postpartum depression. The placenta is rich in hormones: progesterone, estrogen, cortisol, and others. These hormones originate in the placenta, which means a woman’s levels take a plunge immediately after she gives birth. One theory of why women get depressed after birth is their hormone levels are low. Eating the placenta, it seems, could raise hormone levels enough to ward off depression.

I once bought a placental cream in New Zealand, and the hormones in it made my face break out in violent pustules. That doesn’t make me want to eat the stuff.

“It’s spongy like liver,” the woman said, going for the hard sell. She could use it in lieu of meat in any dish: a simple sauté, lasagna, meatloaf, anything. “Placenta” means “cake” in Latin because it’s round and flat; she could make it into a burger. If none of this appeals, she could have it freeze-dried, emulsified, and made into capsules.

“Oh, but I’m vegetarian,” I said, moving my eyes reverently in the direction of a Krishna wall hanging. But the doula-in-training was armed with a response. “Placenta,” she said, “isn’t meat that is killed.” She patted me reassuringly. “It’s OK!”

“I’m OK,” I automatically responded, as if already stuffed and passing on seconds. I didn’t want to burst her bubble, but sautéing, stir-frying, or even baking placenta would likely change the molecular structure of the hormones in it. I suspect she’d have difficulty attracting clients if they had to eat their bloody organ raw, sushi-style.

As it turned out, my obstetrician had a difficult time removing my placenta. Once out, I let my eyes linger on the silver platter it was heaped on. Weighing in at about a pound and a half, this grayish bloody sack fed and protected my daughter and manipulated me for the nearly ten months of pregnancy. It removed her waste. “It’s got to be tough,” I thought.

But regret came over me as I watched it leave the room. Should I have kept it, tried it? I reminded myself there is no proof that consumption of the placenta wards off serious depression or even the baby blues. Humans in traditional cultures only very rarely eat the afterbirth. Hippies ate it but chimps won’t. Many ethnic groups, honoring the placenta’s indispensability, bury it ceremoniously.

I admit a medical incinerator is not a respectful end. But neither is a vegetarian’s hostile gut. I hate to be close-minded, but my jaws are locked shut.

[Click here for an account of a woman who ate the placenta in the pic above.]

Tagged with: , ,

Is there a mommy gene?

Posted in news, pregnancy, science by jenapincott on October 17, 2010

At four o’clock in the morning, in the street in front of our home, I nearly lose it. Our three-week old has been crying for ten hours. I’ve wrestled her into a sling and am jumping up and down under a streetlight, singing “Amazing Grace” in agitated bursts.

Things have taken a turn for the worse. Earlier in the day when I lifted the baby up to my face, eyeball to eyeball, she jerked her head away and cried harder. The infant has been rocked and bounced, shushed and swaddled – with increasing force and desperation. It occurs to me that maybe I should ignore her for a spell. I could lay her down on the dewy grass, let her scream at the stars and the moon, while I drop my head in my hands and weep. How sweet the sound.

If there’s a mommy gene, I don’t have it.

Mommy genes! The idea started about fifteen years ago when a doctoral student named Jennifer Brown and her colleagues at Harvard Medical School noticed something wrong with their mice experiment. Pups were dying. Whole litters, in fact, were wiped out just a day or two after birth. This was strange, because the babies were healthy and so were the mothers. One glance at the mouse cage solved the mystery. Pups were scattered everywhere, shivering and starving, while the mothers nonchalantly went about their business. Normal mother mice round up their brood and feed and lick them. But these dams didn’t give a damn. They acted oblivious to their babies’ frantic squeaks.

The mother mice were specially bred to lack a gene called fosB. Brown and her colleagues had no idea that knocking out fosB would make mice into deadbeat moms, but it apparently does. It turns out that the gene, when activated, creates a protein that turns on other genes and is partly responsible for the function of neurons in the hypothalamus, a region of the brain that controls emotional behavior — including nurture. If you’re a murine mother, just being around your babies usually triggers the fosB gene to express itself. Because mother mice lacking a working copy of the gene are not motherly, fosB hit the headlines as the first “mommy gene.”

Several years later researchers found that genes called Peg 1/Mest and Peg3 also have an effect on the motherliness of mice. When scientists disabled these genes the result was similar the FosB experiment: cold-hearted mothers, empty-bellied pups. Both these genes influence how oxytocin, the “love hormone” behind caressing and nursing and other mothering behavior, is processed in the brain. When oxytocin doesn’t get to where it needs to go, the result is less nurture, more neglect. (Interestingly, in mice and humans, only the Peg1/Mest and Peg3 genes are imprinted and only the one inherited from the father is active. This means an afflicted mouse can blame her lack of mothering instinct on her dads. An attentive one can give him credit. )

“More Mommy genes!” the headlines raved. Mice and humans share many of the same genes, so these genes may influence women’s nurturing instincts, too. Perhaps we can test every wannabe mom to see if she has working copies of FosB, Peg1/ Mest, and Peg3. Then we’ll know who can soothe babies into submission and who thinks it’s a good idea to leave them to cry under the stars. Perhaps we can use genetic engineering to make us supermoms. No new parent would feel exasperated and hopeless again. Let’s make sure everyone has warm fuzzy mommy genes.

The scientists doing this research never claimed they found mommy genes. That sort of bravado would be embarrassing. Humans are obviously more complex than mice, and our behavior is more nuanced.

To say a gene makes a woman a good mother is a little like saying the carburetor is what makes a plane fly. Sure, the plane wouldn’t get off the ground without the device to blend air and fuel. But to credit the carburetor for flight? What about the wings, the pilot, the fuel? Or even the screws and the steel? And what about air around the plane, and the molecules in it? We can’t give all the credit (or blame) to one widget.

The same goes for “mommy genes.” Sure, genes influence how proteins are transcribed and neurons fire and signals are dispatched and hormones are received and processed, and so on. Every part of this infrastructure supports our nurturing behavior. We may be especially deficient if particular genes are defective or if they malfunction. There’s no doubt that researching these genes gives us valuable information about our nurturing behavior. But it’s likely that any one gene is just a widget in what makes us fly.

What’s a good mommy, anyway? That’s a debate beyond the realm of science. It’s slippery. When my newborn finally falls asleep in my arms, angelically, clutching my pinky, I feel like a good mommy again. It doesn’t require mommy genes.

It takes amazing grace.

Tagged with: , ,