Links for Keyword: Sexual Behavior

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By Michael Brooks Occasionally, scientific research comes up with banal findings that should nonetheless stop us in our tracks. For example, researchers recently published a study showing that a father’s brain will change its hormonal outputs and neural activity depending on his parenting duties. The conclusion of the research is, in essence, that men make good parents, too. Surely this is not news. Yet it does provide evidence that is sadly still useful. Those involved with issues of adoption, fathers’ rights, gay rights, child custody, and religion-fuelled bigotry will all benefit from understanding what we now know about what makes a good parent. The biggest enemy of progress has been the natural world, or at least our view of it. Females are the primary caregivers in 95 percent of mammal species. That is mainly because of lactation. Infants are nourished by their mothers’ milk, so it makes sense for most early caring to be done by females. Human beings, however, have developed more sophisticated means of nourishing and raising our offspring. Should the circumstances require a different set-up, we have ways to cope. It turns out that this is not just in terms of formula milk, nannies or day care: We also have a flexible brain. The new study, published in Proceedings of the National Academy of Sciences, scanned the brains of parents while they watched videos of their interactions with their children. The researchers found that this stimulated activity in two systems of the brain. One is an emotional network that deals with social bonding, ensures vigilance and coordinates responses to distress, providing chemical rewards for behaviours that maintain the child’s well-being. The other network is concerned with mental processing. It monitors the child’s likely state of mind, emotional condition, and future needs, allowing for planning. 2014 © The New Republic.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 19883 - Posted: 07.26.2014

By Katherine Harmon Courage Octopuses do the darndest things. Like kill their mate during mating—by strangling him with three arms, according to new observations from the wild. Enterprising scientists Christine Huffard and Mike Bartick watched wild octopuses in action. They found that, for males, mating can be a dangerous game. Especially when your lady has long limbs. Some of the more dicey encounters are detailed in a new paper, published online July 11 in Molluscan Research. Hold on a second, you say. Strangling octopuses? Octopuses don’t even have necks—or inhale air. So how, exactly, does that work? The strangulation seems to happen when “an octopus wraps at least one arm around the base of the mantle of the competitor” (or mate), Huffard wrote in 2010. This constriction then keeps the octopus from taking in fresh water to run past its gills—starving the animal of its oxygen source. Octopuses are not known to get cuddly with one another on a day-to-day basis. In fact, “octopuses touch each other with their arms primarily in the context of mating and aggression,” the researchers write. And in this case it seems to have been both. Huffard came across a pair of mating day octopuses (Octopus cyanea) near Fiabacet Island in Indonesia. The female, as is often the case in this species, was larger—with a body about seven-and-a-half inches long; the male was closer to six inches long. They were positioned on a reef, outside the female’s den, the male’s mating arm (hectocotylus) inserted into the female’s mantle from a (presumably) safe distance. © 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: 19869 - Posted: 07.23.2014

By JAN HOFFMAN As it has for decades, the Centers for Disease Control and Prevention last week released its annual National Health Interview Survey on the health of Americans. But this year, there was a difference: For the first time, the respondents were asked about their sexual orientation. Of 34,557 adults ages 18 and older, the survey reported, 1.6 percent said they were gay or lesbian. Some critics say the numbers are low, but they fall in the range of other surveys. In the new survey, however, only 0.7 percent of respondents described themselves as bisexual; other studies have reported higher numbers. Adults who identified themselves as gay, lesbian or bisexual reported some different behaviors and concerns — for example, more alcohol consumption and cigarette smoking — than those who said they were straight. But it can be difficult to elicit information that many people consider private. The New York Times spoke about such challenges with Gary J. Gates, a demographer at the Williams Institute at the U.C.L.A. School of Law, which focuses on law and policy issues related to sexual orientation and gender identity. Some of Dr. Gates’s findings were echoed in the new survey. This interview was edited and condensed. Q.How was this survey conducted? A.Survey takers had a computer that guided them through questions which they asked the respondent in person, and they used flash cards to show them potential answers. Q.Why do you think the figure for bisexuality was lower than in other surveys? A.There is evidence that bisexuals perceive more stigma and discrimination than gay and lesbian people. They are much less likely to tell important people around them that they are bisexual. © 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: 19862 - Posted: 07.22.2014

By Virginia Morell Many moth species sing courtship songs, and until now, scientists knew of only two types of such melodies. Some species imitate attacking bats, causing a female to freeze in place, whereas others croon tunes that directly woo the ladies. But the male yellow peach moth (Conogethes punctiferalis, pictured) belts out a combination song, scientists report online today in the Proceedings of the Royal Society B. These tiny troubadours, which are found throughout Asia, emit ultrasonic refrains composed of short and long pulses by contracting their abdominal tymbals, sound-producing membranes. (Listen to a male’s courtship song above.) The short pulses, the scientists say, are similar to the hunting calls of insectivorous horseshoe bats. However, unlike other moth species, these males aren’t directing the batlike tunes at females, but rather at rival males. Using playback experiments, the scientists showed that a male drives away competitors with the short pulses of his ditty, while inducing a female to mate with the long note. Indeed, a receptive virgin female moth (1 to 3 days old) typically raises her wings after hearing this part of the male’s song—a sign that she accepts the male, the scientists say. It is thus the first moth species known to have a dual-purpose melody. © 2014 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 19804 - Posted: 07.09.2014

Karen Ravn To the west, the skies belong to the carrion crow. To the east, the hooded crow rules the roost. In between, in a narrow strip running roughly north to south through central Europe, the twain have met, and mated, for perhaps as long as 10,000 years. But although the crows still look very different — carrion crows are solid black, whereas hooded crows are grey — researchers have found that they are almost identical genetically. The taxonomic status of carrion crows (Corvus corone) and hooded crows (Corvus cornix) has been debated ever since Carl Linnaeus, the founding father of taxonomy, declared them to be separate species in 1758. A century later, Darwin called any such classification impossible until the term 'species' had been defined in a generally accepted way. But the definition is still contentious, and many believe it always will be. The crows are known to cross-breed and produce viable offspring, so lack the reproductive barriers that some biologists consider essential to the distinction of a species, leading to proposals that they are two subspecies of carrion crow. In fact, evolutionary biologist Jochen Wolf from Uppsala University in Sweden and his collaborators have now found that the populations living in the cross-breeding zone are so similar genetically that the carrion crows there are more closely related to hooded crows than to the carrion crows farther west1. Only a small part of the genome — less than 0.28% — differs between the populations, the team reports in this week's Science1. This section is located on chromosome 18, in an area associated with pigmentation, visual perception and hormonal regulation. It is no coincidence, the researchers suggest, that the main differences between carrion and hooded crows are in colouring, mating preferences (both choose mates whose colouring matches theirs), and hormone-influenced social behaviours (carrion crows lord it over hooded ones). © 2014 Nature Publishing Group,

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: 19755 - Posted: 06.21.2014

By Denali Tietjen Caffeine isn’t healthy, but that’s no news. The withdrawal headaches, jitteriness and dehydration kind of gave that one way. What is news, however, is that starting at puberty, it’s worse for boys than girls. Girls and boys have the same cardiovascular reactions to caffeine in childhood, but begin to react differently in adolescence, finds a new study conducted by researchers from The University of Buffalo. In the double-blind study published in the June issue of Pediatrics, researchers examined the cardiovascular reactions of 52 pre-pubescent (ages eight to nine) and 49 post-pubescent (ages 15 to 17) children to varying levels of caffeine. Participants consumed either the placebo, 1 mg/kg or 2 mg/kg caffeinated sodas, and then had their heart rates and blood pressures taken. The results found that pre-pubescent children had the same reaction to caffeine regardless of gender, while post-pubescent boys had much stronger cardiovascular reactions to caffeine than girls. The study also examined post-pubescent girls’ reactions to caffeine at various phases of their menstrual cycles. At different stages of the cycle, the girls metabolized caffeine differently. “We found differences in responses to caffeine across the menstrual cycle in post-pubertal girls, with decreases in heart rate that were greater in the mid-luteal phase and blood pressure increases that were greater in the mid-follicular phase of the menstrual cycle,” Dr. Jennifer Temple, one of the researchers who conducted the study said in a University at Buffalo press release announcing the study.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 4: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 4: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
Link ID: 19739 - Posted: 06.17.2014

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