Links for Keyword: Sexual Behavior

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By Jenny Graves The claim that homosexual men share a “gay gene” created a furor in the 1990s. But new research two decades on supports this claim – and adds another candidate gene. To an evolutionary geneticist, the idea that a person’s genetic makeup affects their mating preference is unsurprising. We see it in the animal world all the time. There are probably many genes that affect human sexual orientation. But rather than thinking of them as “gay genes,” perhaps we should consider them “male-loving genes.” They may be common because these variant genes, in a female, predispose her to mate earlier and more often and to have more children. Likewise, it would be surprising if there were not “female-loving genes” in lesbian women that, in a male, predispose him to mate earlier and have more children. We can detect genetic variants that produce differences between people by tracking traits in families that display differences. Patterns of inheritance reveal variants of genes (called “alleles”) that affect normal differences, such as hair color, or disease states, such as sickle cell anemia. Quantitative traits, such as height, are affected by many different genes, as well as environmental factors. It’s hard to use these techniques to detect genetic variants associated with male homosexuality partly because many gay men prefer not to be open about their sexuality. It is even harder because, as twin studies have shown, shared genes are only part of the story. Hormones, birth order and environment play roles, too.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 13: Memory, Learning, and Development
Link ID: 19699 - Posted: 06.06.2014

By MARK OPPENHEIMER When our young daughters first decided to play on top of our Honda minivan, parked in our driveway, my wife was worried. But to me, it seemed no less safe than chasing a ball that frequently ended up in the street. And they loved the height, the novelty, the danger. So I let them stay. They never fell. And with the summer weather here, playing on the car is once again keeping them occupied for hours. Now that I have read Paul Raeburn’s “Do Fathers Matter?,” I know that my comfort with more dangerous play — my willingness to let my daughters stand on top of a minivan — is a typically paternal trait. Dads roughhouse with children more, too. They also gain weight when their wives are pregnant and have an outsize effect on their children’s vocabulary. The presence of dads can delay daughters’ puberty. But older dads have more children with dwarfism and with Marfan syndrome. In Mr. Raeburn’s book, there is plenty of good news for dads, and plenty of bad. A zippy tour through the latest research on fathers’ distinctive, or predominant, contributions to their children’s lives, “Do Fathers Matter?” is filled with provocative studies of human dads — not to mention a lot of curious animal experiments. (You’ll learn about blackbirds’ vasectomies.) But above all, Mr. Raeburn shows how little we know about the role of fathers, and how preliminary his book is. Its end is really a beginning, a prospectus for further research. Mr. Raeburn writes that “as recently as a generation ago, in the 1970s, most psychologists” believed that “with regard to infants, especially, fathers were thought to have little or no role to play.” When it came to toddlers and older children, too, the great parenting theories of the 20th century placed fathers in the background. Freud famously exalted, or damned, the mother for her influence. John Bowlby’s attachment theory, which he developed beginning in the 1940s, focused on the mother or “mother-figure.” © 2014 The New York Times Company

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 19686 - Posted: 06.03.2014

By Denali Tietjen If you watch porn, you probably have a small brain, a new study published in the Journal of the American Medical Association (JAMA) shows. The study, conducted by the Max Plank Institute for Human Development in Berlin, found a significant negative correlation between frequent pornography consumption and grey matter in the brain (that’s the stuff that tells your brain how to react to sensory information.) The keyword here is correlation. While the study’s findings are significant, the researchers don’t know if it’s the porn that causes the low grey-matter volume in porn-watchers, or if it’s the other way around. It could be a neurological pre-condition that makes watching porn particularly satisfying. However, researchers have reason to believe that porn does negatively impact the brain. Previous research proves that frequent porn consumption can cause negative social behavior. Porn consumption can cause viewers to be less satisfied during sex and viewers often want to adopt acts they’ve seen in illegal pornography, according to the report. If porn can affect social behavior, it can probably affect cognitive behavior, too. The study examined the cognitive structure of 64 males ages 21 to 45 years old that consumed porn at varying levels of frequency. While few people openly admit to watching porn, 66 percent of all men and 41 percent of American women view pornography at least once a month, and an estimated 50 percent of internet traffic is sex-related, according to the journal.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 19672 - Posted: 05.31.2014

Elizabeth Norton Cultures around the world have long assumed that women are hardwired to be mothers. But a new study suggests that caring for children awakens a parenting network in the brain—even turning on some of the same circuits in men as it does in women. The research implies that the neural underpinnings of the so-called maternal instinct aren't unique to women, or activated solely by hormones, but can be developed by anyone who chooses to be a parent. "This is the first study to look at the way dads' brains change with child care experience," says Kevin Pelphrey, a neuroscientist at Yale University who was not involved with the study. "What we thought of as a purely maternal circuit can also be turned on just by being a parent—which is neat, given the way our culture is changing with respect to shared responsibility and marriage equality." The findings come from an investigation of two types of households in Israel: traditional families consisting of a biological mother and father, in which the mother assumed most of the caregiving duties, though the fathers were very involved; and homosexual male couples, one of whom was the biological father, who'd had the child with the help of surrogate mothers. The two-father couples had taken the babies home shortly after birth and shared caregiving responsibilities equally. All participants in the study were first-time parents. Researchers led by Ruth Feldman, a psychologist and neuroscientist at Bar-Ilan University in Ramat Gan, Israel, visited with the families in their homes, videotaping each parent with the child and then the parents and children alone. The team, which included collaborators at the Tel Aviv Sourasky Medical Center in Israel, also took saliva samples from all parents before and after the videotaped sessions to measure oxytocin—a hormone that's released at times of intimacy and affection and is widely considered the "trust hormone.” Within a week of the home visit, the participants underwent functional magnetic resonance imaging scanning to determine how their brains reacted to the videotapes of themselves with their infants. © 2014 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 2: Functional Neuroanatomy: The Nervous System and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 2: Cells and Structures: The Anatomy of the Nervous System
Link ID: 19669 - Posted: 05.28.2014

Eliana Dockterman @edockterman A new study that could affect whether adoption agencies are willing to work with gay couples shows that after adopting, gay men's brain activity resembles that of both new moms and new dads Research has shown that a new mother’s brain activity changes after having a baby. Turns out, gay men’s pattern of brain activity also adapts to parenthood, and resembles that of both new moms and new dads, in findings published Monday. A study published Monday in the Proceedings of the National Academy of Sciences sought to determine whether mothers’ brains became hyper-reactive to emotional cues, like hearing their child cry after birth, because of hormonal changes or parenting experience. Researchers videotaped 89 new moms and dads taking care of their infants at home. They then measured parents’ brain activity in an MRI while the parents watched videos in which their children were not featured, followed by the footage shot in their home with their kids. The 20 mothers in the study—all of whom were the primary caregivers—had heightened activity in the brain’s emotion-processing regions; the amygdala, a set of neurons that processes emotions, was five times more active than the baseline. The 21 heterosexual fathers had increased activity in their cognitive circuits, which helped them determine which of the baby’s body movements indicated the need for a new diaper and which ones signaled hunger. The 48 gay fathers’ brain waves, on the other hand, responded similarly to both the heterosexual mom and dad. Their emotional circuits were as active as mothers’, and their cognitive circuits were as active as the fathers’. Researchers also found that the more time a gay father spent with the baby, the greater a connection there was between the emotional and cognitive structures.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 2: Functional Neuroanatomy: The Nervous System and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 2: Cells and Structures: The Anatomy of the Nervous System
Link ID: 19658 - Posted: 05.26.2014

By RONI CARYN RABIN For decades, scientists have embarked on the long journey toward a medical breakthrough by first experimenting on laboratory animals. Mice or rats, pigs or dogs, they were usually male: Researchers avoided using female animals for fear that their reproductive cycles and hormone fluctuations would confound the results of delicately calibrated experiments. That laboratory tradition has had enormous consequences for women. Name a new drug or treatment, and odds are researchers know far more about its effect on men than on women. From sleeping pills to statins, women have been blindsided by side effects and dosage miscalculations that were not discovered until after the product hit the market. Now the National Institutes of Health says that this routine gender bias in basic research must end. In a commentary published on Wednesday in the journal Nature, Dr. Francis Collins, director of the N.I.H., and Dr. Janine A. Clayton, director of the institutes’ Office of Research on Women’s Health, warned scientists that they must begin testing their theories in female lab animals and in female tissues and cells. The N.I.H. has already taken researchers to task for their failure to include adequate numbers of women in clinical trials. The new announcement is an acknowledgment that this gender disparity begins much earlier in the research process. “Most scientists want to do the most powerful experiment to get the most durable, powerful answers,” Dr. Collins said in an interview. “For most, this has not been on the radar screen as an important issue. What we’re trying to do here is raise consciousness.” Women now make up more than half the participants in clinical research funded by the institutes, but it has taken years to get to this point, and women still are often underrepresented in clinical trials carried out by drug companies and medical device manufacturers. © 2014 The New York Times Company

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 19619 - Posted: 05.15.2014

Ewen Callaway In the silk business, sex is money. Male silkworms weave cocoons with more silk of a higher quality than females do, and the multibillion dollar sericulture industry has long sought an easy way to breed only males. That might now be a realistic goal, as researchers have identified the process that determines sex in the silkworm Bombyx mori1. The sex factor is found to be a small RNA molecule — the first time that anything other than a protein has been implicated in a sex-detemination process. In nearly all Lepidoptera — the order that includes moths and butterflies — sex is determined in silkworms by a WZ chromosome system, in contrast to the XY system used in mammals. Female silkworms carry W and Z sex chromosomes, whereas males boast a pair of Z chromosomes. Last year, researchers showed how to genetically modify silkworms so that the females would express a deadly protein (see 'Genetic kill switch eradicates female silkworms for a better crop'). But efforts to identify the genes on the W chromosome that make silkworms female have come up short: the W does not seem to have any protein-making genes, and is instead almost completely filled with parasitic, mobile genetic elements called transposons. In 2011, a team led by entomologist Susumu Katsuma at the University of Tokyo reported that the W chromosome produces short RNA molecules that keep transposons at bay in newly formed egg cells2. Katsuma and his team report in Nature today1 that one such molecule, which the authors called Fem, is specific to female silkworms, suggesting that it has a role in sex determination. The Fem RNA breaks down a corresponding molecule made by a gene known as Masculinizer, which is found on the Z chromosome. When the researchers silenced Masculinizer, embryos execute a genetic programme that makes female tissue. © 2014 Nature Publishing Group

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 19611 - Posted: 05.15.2014

|By Jason G. Goldman When a male fallow deer wants to mate, he isn't shy about letting everyone around him know. The males, also called fallow bucks, can produce their mating calls as many as 3,000 times each hour during the mating season. Those calls serve two functions: to attract females and to deter rival males. Yet there is more hidden in the groans of fallow bucks than first meets the ear, according to a new study in Behavioral Ecology. Every October around 25 bucks gather in Petworth Park in England's county of West Sussex, where each stakes out a territory, hoping to entice a female at a feral conclave of romance, combat and deer calling, an event known as a lek. “Leks are really rare in mammals, and they're really rare in ungulates. Fallow deer are the only species of deer that we know that lek,” says Alan McElligott of Queen Mary, University of London, who oversaw the study. Mating calls reveal information about the caller, such as body size or dominance rank, which is useful both to interested females and to rival males—and every conceivable type of fallow deer utterance turns up at the lek. In one study, McElligott found that the quality of groans decreased over time. “The mature bucks stop eating for a couple of weeks,” over the course of the lek, McElligott explains, so “they are really worn out.” That fatigue is reflected in their calls, but do other males notice? Because the lek is such a spectacle, the deer in Petworth Park are accustomed to human interlopers, which allowed Queen Mary postdoctoral scholar Benjamin J. Pitcher to cart a sound system around without interrupting the festivities. © 2014 Scientific American

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 19599 - Posted: 05.12.2014

The gene that most likely determines the sex of the platypus and echidna has been identified by Australian and Swiss researchers. The study also shows that the Y chromosome, contrary to previous assumptions, carries genes that are important to the basic viability of male mammals, says geneticist Dr Paul Waters from the University of New South Wales. Although the Y chromosome is known to be important in sex determination, little is known about the function and evolution of its genes, says Waters. He says this is because it has so many repetitive and palindromic sequences, which make it hard to reconstruct the true sequences of its genes from fragments of sequenced DNA. Monotremes (the platypus and the echidna), whose males have 5 X chromosomes and 5 Y chromosomes, are especially challenging. "No one had really characterised any Y chromosomes in platypus before because they've got quite a complex sex chromosome system," says Waters. Waters and colleagues from the University of Adelaide and the University of Lausanne now report on their new analysis of male and female DNA from 15 representative mammals, including human, elephants, marsupials and monotremes. The study, reported recently in the journal Nature, is the largest of its kind, and relied on a rapid new sequencing technique. © 2014 Discovery Communications, LLC.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 19582 - Posted: 05.07.2014

A UBC neuroscientist says motherhood permanently alters the brain, exposing moms to different health risks than women without children. Liisa Galea, a professor in the university's psychology department, says some changes are temporary while others are permanent. The most obvious example is size. According to Galea, a mother's brain shrinks by up to eight per cent during pregnancy. While it bounces back about six months after birth, she notes the reaction could have repercussions. “Our research shows that, as a result of these transformations, mothers experience different cognitive abilities and health risks than women without children,” said Galea. And she warns that women who’ve borne children may even react to medication differently. “If mothers’ brains are different than other women’s brains, as our research finds, it means we must embrace greater personalization of medical care – not only for men versus women, but even among women with different life experiences,” she said. But that’s a challenge that may be insurmountable given that medical research studies at the animal model level have relied predominantly on the use of male rats. “Why would we assume that what works in a male rat automatically works in a female patient before testing it on a female rat?” questioned Galea. She claims one of the big failures of translational studies is that most fail to acknowledge how subjects’ gender, or other unique characteristics, like motherhood, plays a role. © CBC 2014

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 8: Hormones and Sex
Link ID: 19561 - Posted: 05.03.2014

Guys, do you prefer more feminine faces? If so, chances are you grew up in a relatively healthy place. New research suggests that men raised in countries with higher average lifespans and lower child mortality more strongly prefer women with softer features than do men raised in less healthy nations. The finding bolsters the idea that years of human evolution have made men attracted to faces that could help them survive. Previous studies have found that women living in harsher conditions—such as communities with high homicide rates and low income—are more inclined to find more masculine men attractive. Urszula Marcinkowska, a biologist at the University of Turku in Finland, and her colleagues wanted to know whether culture also influenced males’ preferences for females, or whether men judged females in a more universal way. Using an online survey conducted in 16 different languages, the researchers presented 1972 heterosexual males between the ages of 18 and 24 from 28 different countries with 20 pairs of Caucasian female faces. Each pair contained one face with more feminine traits—such as larger eyes, fuller lips, and a less angular jaw—as well as a more androgynous face, with thinner lips and a wider chin. Participants were asked to select which face in each pair they found more sexually attractive. While men across all cultures generally preferred a more feminine face, the strength of that preference varied between countries. The difference couldn’t be explained by the ratio of men to women in a country, its gross national income, or the race of the participants, but it did correlate with the national health index of the men’s countries—a measure of overall well-being. Those from countries like Japan, with high national health index scores, chose the more feminine face more than three-quarters of the time, the authors report online today in Biology Letters. Men from countries such as Nepal, which has a lower health rating, selected the more feminine face in only slightly more than half of the cases, on average. © 2014 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 8: Hormones and Sex
Link ID: 19555 - Posted: 04.30.2014

THAT health and beauty are linked is not in doubt. But it comes as something of a surprise that who is perceived as beautiful depends not only on the health of the person in question but also on the average level of health in the place where she lives. This, though, is the conclusion of a study just published in Biology Letters by Urszula Marcinkowska of the University of Turku, in Finland, and her colleagues—for Ms Marcinkowska has found that men in healthy countries think women with the most feminine faces are the prettiest whilst those in unhealthy places prefer more masculine-looking ones. Ms Marcinkowska came to this conclusion by showing nearly 2,000 men from 28 countries various versions of the same female faces, modified to look less or more feminine, and thus reflect the effects of different levels of oestrogen and testosterone. Oestrogen promotes features, such as large eyes and full lips, that are characteristically feminine. Testosterone promotes masculine features, such as wide faces and strong chins. As the chart shows, the correlation is remarkable—and statistical analysis shows it is unconnected with a country’s wealth or its ratio of men to women and thus the amount of choice available to men. The cause, though, is unclear. Previous studies have shown that women with feminine features are more fertile. A man’s preference for them is thus likely to enhance his reproductive success. Ms Marcinkowska speculates that testosterone-induced behavioural characteristics like dominance, which might be expected to correlate with masculine-looking faces even in women (they certainly do in men), help in the competition for resources needed to sustain children once they are born. But why that should be particularly important in an unhealthy country is unclear.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 8: Hormones and Sex
Link ID: 19554 - Posted: 04.30.2014

by Laura Sanders When a baby cries at night, exhausted parents scramble to figure out why. He’s hungry. Wet. Cold. Lonely. But now, a Harvard scientist offers more sinister explanation: The baby who demands to be breastfed in the middle of the night is preventing his mom from getting pregnant again. This devious intention makes perfect sense, says evolutionary biologist David Haig, who describes his idea in Evolution, Medicine and Public Health. Another baby means having to share mom and dad, so babies are programmed to do all they can to thwart the meeting of sperm and egg, the theory goes. Since babies can’t force birth control pills on their mothers, they work with what they’ve got: Nighttime nursing liaisons keep women from other sorts of liaisons that might lead to another child. And beyond libido-killing interruptions and extreme fatigue, frequent night nursing also delays fertility in nursing women. Infant suckling can lead to hormone changes that put the kibosh on ovulation (though not reliably enough to be a fail-safe birth control method, as many gynecologists caution). Of course, babies don’t have the wherewithal to be interrupting their mothers’ fertility intentionally. It’s just that in our past, babies who cried to be nursed at night had a survival edge, Haig proposes. The timing of night crying seems particularly damning, Haig says. Breastfed babies seem to ramp up their nighttime demands around 6 months of age and then slowly improve — precisely the time when a baby would want to double down on its birth control efforts. © Society for Science & the Public 2000 - 2013

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 19539 - Posted: 04.26.2014

Here to stay. The Y chromosome is small compared with the X, but is required to keep levels of some genes high enough for mammals to survive. The small, stumpy Y chromosome—possessed by male mammals but not females, and often shrugged off as doing little more than determining the sex of a developing fetus—may impact human biology in a big way. Two independent studies have concluded that the sex chromosome, which shrank millions of years ago, retains the handful of genes that it does not by chance, but because they are key to our survival. The findings may also explain differences in disease susceptibility between men and women. “The old textbook description says that once maleness is determined by a few Y chromosome genes and you have gonads, all other sex differences stem from there,” says geneticist Andrew Clark of Cornell University, who was not involved in either study. “These papers open up the door to a much richer and more complex way to think about the Y chromosome.” The sex chromosomes of mammals have evolved over millions of years, originating from two identical chromosomes. Now, males possess one X and one Y chromosome and females have two Xs. The presence or absence of the Y chromosome is what determines sex—the Y chromosome contains several genes key to testes formation. But while the X chromosome has remained large throughout evolution, with about 2000 genes, the Y chromosome lost most of its genetic material early in its evolution; it now retains less than 100 of those original genes. That’s led some scientists to hypothesize that the chromosome is largely indispensable and could shrink away entirely. © 2014 American Association for the Advancement of Science.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 19531 - Posted: 04.24.2014

It takes a lot to deter a male from wanting sex. A new study has found that male mice keep trying to copulate even when they are in pain, whereas females engage in less sex. But when given drugs that target pleasure centers in the human brain, the females again became interested. The findings could shed light on the nature of libido across various animal species. To assess how pain influences sexual desire, researchers first identified pairs of mice that wanted to have sex. “What we found early on was not all mice will mate with each other,” says clinical psychologist Melissa Farmer, who led the study while earning her Ph.D. at McGill University in Montreal, Canada. The team set up the rodents on a series of “dates,” during which a male and female were paired together for 30 minutes. Couples that copulated for most of the session were deemed compatible and moved into a cage with separate rooms. A small doorway allowed a female mouse to freely cross over from her chamber, but the male—which is larger—could not. The scientists then induced pain in males or females by applying a small dose of inflammatory compounds to the cheek, tail, foot, or genitals. The sensation would primarily be soreness, like a bad sunburn, says Farmer, who now works at Northwestern University’s Feinberg School of Medicine in Chicago, Illinois. Female mice that were in pain, whether genital or nongenital, spent 50% less time with their male partners, implying a decrease in sexual motivation. Even when they did visit their paramours, females wouldn’t allow males to mount them with the same frequency, the team reports online today in The Journal of Neuroscience. © 2014 American Association for the Advancement of Science.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 5: The Sensorimotor System
Link ID: 19526 - Posted: 04.23.2014

by Bethany Brookshire Every hipster knows that something is only cool before it becomes popular. There’s no point in liking a band once it hits the big time. That shirt is no good once it’s no longer ironic. And it’s certainly not enough to go clean shaven or grow a short beard — that’s much too mainstream. Recent years have seen a resurgence of moustaches, mutton chops and Fu Manchus. A style that really stands out sticks it to conformity. It turns out that when people buck the facial hair trend, they may end up making themselves more attractive. A new study published April 16 in Biology Letters shows that either clean-shaven or fully bearded looks become more attractive when they are rare in the population. The study suggests that humans may practice what’s called negative frequency-dependent selection — people rate rare looks as more attractive than they might otherwise. But when we try to figure out why, the interpretations can get pretty hairy. In every population, there is variation, both in genetics and in how individuals look. But at first blush, this variation doesn’t make a lot of sense. If one particular look is the most attractive and best for the population, sexual selection should make a species converge on a single, popular look. For example, if the best male guppies have stripes, soon all male guppies will have stripes, as females will only mate with stripey males. But in nature, this is clearly not the case. Guppies come in a wild variety of patterns, and so do humans. In guppies, this variation is a result of negative frequency-dependent selection: Female guppies prefer male guppies that look unusual compared to others, rather than guppies that share common features. This helps keep looks and genes variable, a distinct advantage for the species. So an individual guppy’s attractiveness doesn’t just depend on his shining character, it depends on how rare his looks are in relation to other guppies. © Society for Science & the Public 2000 - 2013

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 14: Attention and Consciousness
Link ID: 19493 - Posted: 04.16.2014

by Agata Blaszczak-Boxe, LiveScience.com Unlike many humans, some monkeys are genuinely faithful to their mates. A species known as Azara's owl monkeys tends to be monogamous, according to a new study of these primates. The research also found that the monkeys' inclination to be faithful was related to the male monkeys' tendency to care for their offspring. "They [Azara's owl monkeys] live in pairs, so, in a group, we have only one adult male and one adult female, and both of them are faithful," study author Maren Huck, a professor at the University of Derby in England, told Live Science. "We found a link between... parental care and having few instances of cheating," Huck said. Researchers had known before this study that members of the Azara's species were socially monogamous, which means that males and females live in pairs. But in animals, including humans, social monogamy is not always equivalent to what researchers call genetic monogamy, where females and males only reproduce with their mates. One way researchers can check for genetic monogamy is to analyze the DNA of mating pairs, and check the paternity of the offspring. In the study, the researchers analyzed field observations of the monkeys' behavior, along with genetic samples from a total of 128 monkeys, including some that lived in groups, and others that were solitary "floaters." The material used by the research team included samples from 35 offspring that were born to 17 reproducing pairs. © 2014 Discovery Communications, LLC

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 19484 - Posted: 04.15.2014

By KATRINA KARKAZIS and REBECCA JORDAN-YOUNG In 2009, the South African middle-distance runner Caster Semenya was barred from competition and obliged to undergo intrusive and humiliating “sex testing” after fellow athletes at the Berlin World Championships questioned her sex. Ms. Semenya was eventually allowed to compete again, but the incident opened the world’s eyes to the process of sex testing and the distress it could bring to an athlete who had lived her whole life as a girl. When an endocrinologist, a gynecologist and a psychologist were brought in to determine whether the teenager was really a woman, she simply asserted, “I know who I am.” From 2011, major sports governing bodies, including the International Olympic Committee, the Fédération Internationale de Football Association and the International Association of Athletics Federations, instituted new eligibility rules that were intended to quell the outrage over the handling of the Semenya case. Instead, as recent cases attest, they may have made things worse. Rather than trying to decide whether an athlete is “really” female, as decades of mandatory sex tests did, the current policy targets women whose bodies produce more testosterone than is typical. If a female athlete’s T level is deemed too high, a medical team selected by the sport’s governing bodies develops a “therapeutic proposal.” This involves either surgery or drugs to lower the hormone level. If doctors can lower the athlete’s testosterone to what the governing bodies consider an appropriate level, she may return to competition. If she refuses to cooperate with the investigation or the medical procedures, she is placed under a permanent ban from elite women’s sports. © 2014 The New York Times Company

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 19471 - Posted: 04.12.2014

Julia Baird SYDNEY, Australia — PRETTY much the No. 1 question you are asked when you’re pregnant is: “Girl or boy?” If you choose not to find out, but to be deliciously surprised at birth, as I did, then you will be asked to guess: “What do you feel it is?” I used to scrunch up my eyes and try hard to draw on what people told me was an age-old female intuition: Which genitals were sprouting in my round belly? I could never tell, though. It is as though the entire world is trying to guess what, or who, is inside you. One oft-told tale is that girls steal your looks and make you fat, while boys just make your belly stick out straight. When I stood wearily bulging at one friend’s baby shower in Manhattan, a stylist confided that she thought our mutual friend was having a boy, because she looked so pretty. Then she looked me up and down: “I think you’re having a girl.” (I placed her in the same category as the neighbor who yelled, “Morning, Fatty!” over the side fence each day.) Why is whether a baby wears blue or pink the most pressing matter for adult acquaintances of a soon-to-be-born? Green is just fine, or white. But a 2007 Gallup poll found that most young Americans, and women under 50, would like to find out the sex of their baby before it is born. In some American fertility clinics, staff experts check the embryo’s sex before they implant it in the womb. So what will it do to our collective minds when forced to grasp that some people are neither gender? Not male, or female, but something else either encompassing, or rejecting, or just adapting from both? Last week, Australia had to grapple with just that after the High Court, in a historic decision, ruled that a person called Norrie May-Welby could register as “nonspecific” on official certificates. Now 52, Norrie was identified, physically, as male when she was born, in Scotland, but was drawn to the world of girls, playing with dolls at age 4 and tying her school tie around her head at night to create the illusion of long hair. She escaped into the library monitors’ group at school and made up adventures where she played six characters, five of whom were female: “I didn’t think there was any problem with this,” she says. “After all, just because I wasn’t really from Krypton, didn’t mean I couldn’t imagine being Supergirl.” © 2014 The New York Times Company

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 19462 - Posted: 04.09.2014

By: Larry Cahill, Ph.D. Early in 2013, the Food and Drug Administration (FDA) ordered the makers of the well-known sleep aid Ambien (zolpidem) to cut their recommended dose in half-but only for women. In essence, the FDA was acknowledging that despite extensive testing prior to the drug's release on the market, millions of women had been overdosing on Ambien for 20 years. On February 9, 2014, CBS's 60 Minutes highlighted this fact-and sex differences in general-by powerfully asking two questions: Why did this happen, and are men and women treated equally in research and medicine?1 The answer to the first question is that the biomedical community has long operated on what is increasingly being viewed as a false assumption: that biological sex matters little, if at all, in most areas of medicine. The answer to the second question is no, today's biomedical research establishment is not treating men and women equally. What are some of the key reasons for the biomedical community's false assumption, and why is this situation now finally changing? What are some of the seemingly endless controversies about sex differences in the brain generated by "anti-sex difference" investigators? And what lies at the root of the resistance to sex differences research in the human brain? For a long time, for most aspects of brain function, sex influences hardly mattered to the neuroscience mainstream. The only sex differences that concerned most neuroscientists involved brain regions (primarily a deep-brain structure called the hypothalamus) that regulate both sex hormones and sexual behaviors.2 Neuroscientists almost completely ignored possible sex influences on other areas of the brain, assuming that the sexes shared anything that was fundamental when it came to brain function. Conversely, the neuroscience mainstream viewed any apparent sex differences in the brain as not fundamental- something to be understood after they grasped the fundamental facts. By this logic, it was not a problem to study males almost exclusively, since doing so supposedly allowed researchers to understand all that was fundamental in females without having to consider the complicating aspects of female hormones. To this day, neuroscientists overwhelmingly study only male animals.3 © 2014 The Dana Foundation

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 19461 - Posted: 04.09.2014