Chapter 12. Sex: Evolutionary, Hormonal, and Neural Bases

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By Paul D. Thacker When the FDA denied Sprout Pharmaceutical’s bid last October to begin marketing flibanserin, a drug aimed at treating low sexual desire in women, women’s groups responded in anger. In January, representatives from eight different women’s groups, including the National Organization of Women, met with Janet Woodcock, the FDA’s head of pharmaceuticals, to protest the decision. Congress also got in on the act, with Reps. Debbie Wasserman Schultz, Chellie Pingree, Nita Lowey, and Louise Slaughter sending a letter to FDA Commissioner Margaret Hamburg to implore that, when evaluating drugs for female dysfunction (in medical terms Hypoactive Sexual Desire Disorder, or HSDD), Dr. Hamburg apply "the same standards of consideration given to the approved drugs for men in your risk/benefit evaluation." “We’ve now got 24 drugs for men for either testosterone replacement or erectile dysfunction,” Cindy Whitehead, Sprout’s chief operating officer told the Associated Press. “Yet there are zero drugs for the most common form of sexual dysfunction in women.” Anita H. Clayton, the interim chair of the department of psychiatry and neurobehavioral sciences at the University of Virginia School of Medicine, was more explicit, writing in a blistering column for the Huffington Post: “For the millions of women with HSDD, the FDA must overcome the problem of institutionalized sexism—unconscious and perhaps unintended, but damaging nonetheless.” The chorus was loud and clear: The FDA is sexist. The federal agency charged with approving drugs to protect and improve our health is now standing in the way of a woman’s right to have a satisfying sex life. This framing played out in numerous stories, with similar charges appearing in the American Prospect (“the FDA’s kinda sexist”), and the Washington Post (“Some critics say the agency—consciously or not—may be succumbing to society’s squeam­ishness about women’s sexual desires compared with those of men”). Not to be outdone with mere institutional sexism, a writer for the Wire mused whether “blatant, medieval sexism is also at play.” © 2014 The Slate Group LLC.

Keyword: Sexual Behavior
Link ID: 19458 - Posted: 04.08.2014

By SINDYA N. BHANOO Monogamy is rare in animals. Even among species that pair off, there is often philandering. But a new genetic analysis adds to the evidence that the South American primates called Azara’s owl monkeys are remarkably faithful to their partners. The study confirms what one of its authors, Eduardo Fernandez-Duque, an evolutionary anthropologist at the University of Pennsylvania who leads the Owl Monkey Project, had long suspected. For 18 years, he and other Penn researchers have been observing the Azara’s owl monkey in the Chaco region of Argentina. Not only have they never witnessed a philanderer, but they have also found that infant owl monkeys get an unusual amount of care from their fathers. “The male plays with the infant and the male shares food with the infant even more than the mother,” Dr. Fernandez-Duque said. “The males care because these are their offspring, and this has a direct benefit in terms of reproductive success.” In the new study, published in the Proceedings of the Royal Society B, the researchers performed genetic analysis on 35 offspring born to 17 owl monkey pairs and confirmed that the parents were monogamous for the mating season. The monkey is the first primate and only the fifth mammal for which monogamy has been verified through genetics. Because paternal care is also seen in other species of owl monkeys, the scientists suspect that they, too, are serially monogamous. © 2014 The New York Times Company

Keyword: Sexual Behavior; Aggression
Link ID: 19422 - Posted: 03.29.2014

by Clare Wilson It's a vicious circle of the cruellest kind. Stress might be causing infertility in women, according to new research. This could explain some cases in which couples are diagnosed as infertile with no apparent cause. Taking longer than usual to conceive can lead to stress, so the problem could become self-perpetuating. A link between everyday life stresses and infertility has long been suspected, but there has been little hard evidence connecting the two. Women receiving fertility treatment are generally advised to avoid stress, but not so the average person trying to conceive. An estimated one in seven couples in the UK have fertility problems and, in about a quarter of those, there is no known medical explanation, and they are given a diagnosis of "unexplained infertility". To explore the role of stress, Courtney Lynch at Ohio State University in Columbus and her colleagues collected saliva samples from 373 women in the US who had just started trying to conceive naturally and measured levels of an enzyme called alpha-amylase, a marker of stress. After one year of regular unprotected sex, about 13 per cent of the couples had failed to get pregnant, the standard definition of infertility. The third of women who had the highest alpha-amylase levels were twice as likely to be in the infertile group as the third with the lowest levels. In a previous study, Lynch's team found that those with higher levels of the stress enzyme were slightly less likely to conceive in their first month of trying. But this is the first time that alpha-amylase has been linked to clinical infertility. © Copyright Reed Business Information Ltd.

Keyword: Stress; Aggression
Link ID: 19400 - Posted: 03.24.2014

By BENOIT DENIZET-LEWISy The traffic was bad, even by the warped standards of a Southern California commute. We were headed south from Los Angeles to San Diego on an overcast morning last spring, but we hadn’t moved in 10 minutes. I was sandwiched in the back seat of the car between John Sylla and Denise Penn, two board members of the Los Angeles-based American Institute of Bisexuality (A.I.B.), a deep-pocketed group partly responsible for a surge of academic and scientific research across the country about bisexuality. We were on our way to an A.I.B. board meeting, where members would decide which studies to fund and also brainstorm ways to increase bisexual visibility “in a world that still isn’t convinced that bisexuality — particularly male bisexuality — exists,” as Allen Rosenthal, a sex researcher at Northwestern University, told me. When someone suggested that we try another route, Sylla, A.I.B.’s friendly and unassuming 55-year-old president, opened the maps app on his iPhone. I met Sylla the previous day at A.I.B. headquarters, a modest two-room office on the first floor of a quiet courtyard in West Hollywood that’s also home to film-production companies and a therapist’s office. Tall and pale, with an easy smile, Sylla offered me books from A.I.B.’s bisexual-themed bookshelf and marveled at the unlikelihood of his bisexual activism. “For the longest time, I didn’t even realize I was bi,” Sylla said. “When I did, I assumed I’d probably just live a supposedly straight life in the suburbs somewhere.” In the back seat, Sylla lifted his eyes from his phone and suggested an alternate course. Then he shrugged his shoulders. “We could go either way, really,” he told us. He smiled at me. “Get it? Either way?” © 2014 The New York Times Company

Keyword: Sexual Behavior; Aggression
Link ID: 19397 - Posted: 03.22.2014

by Barbara J. King Why do little boys tend to behave differently from little girls? Why do boys and girls play differently, for instance, choosing different toys as their favorites? Ask these questions and you invite a firestorm — of more questions. Is the premise behind these queries even accurate? Aren't our sons and daughters really more similar than different, after all? And when behavioral sex differences do occur, aren't parents who inflict sex-stereotypical expectations on their children largely responsible? Seven experts on chimpanzee behavior, led by of Franklin and Marshall College and including the world-famous primatologist , have in Animal Behaviour that speaks, they say, to these issues. Their data on wild chimpanzees from , Tanzania, indicate that human sex differences in childhood are primarily the result of biological, evolutionary mechanisms. The scientists analyzed data on the behavior of 12 male and eight female chimpanzee youngsters, ages 30-36 months. At that age, chimpanzees, who develop quite slowly compared with many other mammals, are still considered infants. As a rule, chimpanzees spend most of their day in close proximity to their mothers clear through their ninth year of life. In the Gombe study, male infants were found to be more gregarious than female chimpanzees; they interacted with significantly more individuals outside the immediate family, including more adult males, than did females. This result held even when the number of the mothers' social partners was controlled. ©2014 NPR

Keyword: Sexual Behavior; Aggression
Link ID: 19395 - Posted: 03.22.2014

by Ashley Yeager Owl monkeys don't sleep around, genetic tests show. That could be a result of the amount of care males provide for their young, a new study suggests. Infidelity appears to be common in mammals that live in pairs. But new genetic tests suggest that Azara's owl monkeys are unusually faithful. Scientists studied 35 infants born to 17 owl monkey pairs and found that in all cases the youngsters were being raised by their biological parents. Data from the owl monkeys and 14 other species showed that the more involved the males were in raising an infant, the more likely the males were to be faithful, the team reports March 18 in Proceedings of the Royal Society B. Owl monkeys are the only primates and one of five mammal species, including coyotes and California mice, that don’t seem to cheat, according to genetic studies. The evolution of animals’ sexual fidelity is probably linked to the intensity of male care, the researchers suggest. © Society for Science & the Public 2000 - 2013.

Keyword: Sexual Behavior
Link ID: 19386 - Posted: 03.20.2014

By Maggie Fox and Erika Edwards Women are carrying the bigger burden of Alzheimer’s disease in the U.S., according to a new report — making up not only most of the cases, but paying more of the cost of caring for the growing population of people with the mind-destroying illness. The new report from the Alzheimer’s Association paints Alzheimer’s as a disease that disproportionately affects women, both as patients and as caregivers. It points out that women in their 60s are about twice as likely to develop Alzheimer’s over the rest of their lives as they are to develop breast cancer. “So women are at the epicenter of Alzheimer's disease today, not only by being most likely to be diagnosed with Alzheimer's, but also by being the caregiver most of the time,” said Maria Carrillo, vice president of the advocacy group. Alzheimer’s affects more than 5 million Americans, a number projected to soar to 13 million over the next 35 years. A study published earlier this year suggested it’s a big killer, taking down more than 500,000 Americans every year. Three out of five of those living with Alzheimer’s are women, the report finds. “The surprising statistic we pulled out of this report actually is that women over 65 have a one in six chance of developing Alzheimer's disease, in comparison to one out of 11 in men,” Carrillo said. And that compares to a one in eight lifetime risk for developing breast cancer.

Keyword: Alzheimers; Aggression
Link ID: 19381 - Posted: 03.19.2014

By Ella Davies Reporter, BBC Nature The whales are known for their tusks which can reach 2.6m (9ft) in length, earning them comparisons with mythological unicorns. The tusk is an exaggerated front tooth and scientists have discovered that it helps the animals sense changes in their environment. Dr Martin Nweeia from the Harvard School of Dental Medicine, US, undertook the study alongside an international team of colleagues. Through the years, many theories have tried to explain the function of the narwhal's impressive tusk. "People have said it's everything from an ice pick to an acoustic probe, but this is the first time that someone has discovered sensory function and has the science to show it," said Dr Nweeia. More recently, experts have agreed that the tusk is a sexual characteristic because it is more often exhibited by males and they appear to use them during fights to assert their social hierarchy. But because the animals are rarely seen, the exact function of the tusk has remained a mystery. Previous studies have revealed that the animals have no enamel on their tusk - the external layer of the tooth that provides a barrier in most mammal teeth. Dr Nweeia and the team's analysis revealed that the outer cementum layer of the tusk is porous and the inner dentin layer has microscopic tubes that channel in towards the centre. In the middle of the tusk lies the pulp, where nerve endings which connect to the narwhal's brain are found. BBC © 2014

Keyword: Pain & Touch; Aggression
Link ID: 19374 - Posted: 03.18.2014

by Bethany Brookshire Spring will be here soon. And with daffodils, crocuses and other signs of spring comes a burst of birdsong as males duke it out to get female attention. While the males trill loud songs, the females sit quietly, choosing who will be the lucky male. Vocal male and quiet female songbirds are common in temperate zones, and have given rise to a common assumption. The best male songs get picked for reproduction, and this sexual selection results in complex song; females just listen and choose, so female song should be rare. After all, females don’t need to sing to attract mates. But it turns out this commonly held assumption is not true. A new study shows that the majority of females of songbird species do sing, and it’s likely that the ancestor of modern songbirds was also a vocal diva. The results challenge the old wisdom about female songbirds, and suggest that when it comes to female song, it’s not all about sex. Karan Odom, a behavioral ecologist at the University of Maryland, Baltimore County, has always been interested in birdsong. “As I began to study it in depth,” she says, “I realized there was a lot that’s unknown, and one area was the extent to which females were singing and the role that song plays in males and females.” Odom and her colleagues did a survey of 44 songbird families, going through bird handbooks and other sources to find records of whether males, females or both were singers. In results published March 4 in Nature Communications, they showed that female melodies are not rare at all. In fact, 71 percent of the species surveyed have singing ladies. So much for that quiet, retiring female bird. © Society for Science & the Public 2000 - 2013.

Keyword: Sexual Behavior; Aggression
Link ID: 19361 - Posted: 03.13.2014

By Ella Davies Reporter, BBC Nature Peacocks make fake sex sounds to attract females' attention, scientists say. The birds are known for shaking their tail feathers but Canadian researchers have revealed a further sexual tactic. Peacocks have a wide vocabulary of calls, and during mating they make a distinctive hoot. Biologists also recorded males making this sound when out of sight of females and suggest such deception could prove rewarding for the birds. Peacocks are one of the most obvious examples of advertising sexual fitness in the animal kingdom with their eye-catching plumage and strutting courtship displays. The mating behaviour takes place in open areas of land referred to as a "lek". When a male has successfully attracted a female, or peahen, it rushes at her making a distinctive hooting call before attempting to mate. These calls are loud enough to be heard from a distance, prompting scientists to investigate what benefit this has. "It's much louder than it needs to be to communicate with just the female that the male is trying to mate with," explained Dr Roslyn Dakin from the University of British Columbia, Canada, who co-authored the study. BBC © 2014

Keyword: Sexual Behavior
Link ID: 19352 - Posted: 03.12.2014

by Colin Barras Treat them mean, keep them keen? Female preying mantis and black widow spiders are notorious for their tendency to kill and eat males before, during or after sex. The behaviour is clearly risky, though – not least because the scent of a dead rival hardly encourages other males to try their luck. Or so we thought. For male Pennsylvania grass spiders, the whiff of dead male seems to be exactly what they look for in a mate. They are far more likely to approach a female if she has recently killed and eaten a male. Grass spiders are found across North America. With a body length – not including legs – of 17 millimetres, the Pennsylvania grass spider is among the largest. It's harmless to humans, though, spending most of its time hiding away in a tunnel at the corner of its flat, sheet-like web. Unlike many arachnids, grass spiders don't produce sticky webs. But they can move surprisingly quickly, dashing out of their tunnel to grab any insect that ventures too near. It's not just insects that have reason to fear female Pennsylvania grass spiders. Males of the species can find themselves on the wrong end of a female's voracious appetite when the two meet to breed. As mating strategies go, it seems a pretty foolhardy one: studies suggest females in urban settings are typically approached by no more than three – and as few as zero – males during their 3-week-long breeding season. Cannibalism seems to leave the females at risk of self-inflicted celibacy. © Copyright Reed Business Information Ltd

Keyword: Sexual Behavior
Link ID: 19351 - Posted: 03.12.2014

Think women can’t do math? You’re wrong—but new research shows you might not change your mind, even if you get evidence to the contrary. A study of how both men and women perceive each other's mathematical ability finds that an unconscious bias against women could be skewing hiring decisions, widening the gender gap in mathematical professions like engineering. The inspiration for the experiment was a 2008 study published in Science that analyzed the results of a standardized test of math and verbal abilities taken by 15-year-olds around the world. The results challenged the pernicious stereotype that females are biologically inferior at mathematics. Although the female test-takers lagged behind males on the math portion of the test, the size of the gap closely tracked the degree of gender inequality in their countries, shrinking to nearly zero in emancipated countries like Sweden and Norway. That suggests that cultural biases rather than biology may be the better explanation for the math gender gap. To tease out the mechanism of discrimination, two of the authors of the 2008 study, Paola Sapienza and Luigi Zingales, economic researchers at Northwestern University’s Kellogg School of Management in Evanston, Illinois, and the University of Chicago Booth School of Business in Illinois, respectively, teamed up with Ernesto Reuben, an experimental psychologist at Columbia Business School in New York City, to design an experiment to test people's gender bias when it comes to judging mathematical ability. Study participants of both genders were divided into two groups: employers and job candidates. The job was simple: As accurately and quickly as possible, add up sets of two-digit numbers in a 4-minute math sprint. (The researchers did not tell the subjects, but it is already known that men and women perform equally well on this task.) © 2014 American Association for the Advancement of Science.

Keyword: Sexual Behavior; Aggression
Link ID: 19348 - Posted: 03.11.2014

By Jessica Wright and SFARI.org It takes more mutations to trigger autism in women than in men, which may explain why men are four times more likely to have the disorder, according to a study published 26 February in the American Journal of Human Genetics. The study found that women with autism or developmental delay tend to have more large disruptions in their genomes than do men with the disorder. Inherited mutations are also more likely to be passed down from unaffected mothers than from fathers. Together, the results suggest that women are resistant to mutations that contribute to autism. “This strongly argues that females are protected from autism and developmental delay and require more mutational load, or more mutational hits that are severe, in order to push them over the threshold,” says lead researcher Evan Eichler, professor of genome sciences at the University of Washington in Seattle. “Males on the other hand are kind of the canary in the mineshaft, so to speak, and they are much less robust.” The findings bolster those from previous studies, but don't explain what confers protection against autism in women. The fact that autism is difficult to diagnose in girls may mean that studies enroll only those girls who are severely affected and who may therefore have the most mutations, researchers note. “The authors are geneticists, and the genetics is terrific,” says David Skuse, professor of behavioral and brain sciences at University College London, who was not involved in the study. “But the questions about ascertainment are not addressed adequately.” © 2014 Scientific American

Keyword: Autism; Aggression
Link ID: 19347 - Posted: 03.11.2014

Why do some humans have lighter skin than others? Researchers have longed chalked up the difference to tens of thousands of years of evolution, with darker skin protecting those who live nearer to the equator from the sun’s intense radiation. But a new study of ancient DNA concludes that European skin color has continued to change over the past 5000 years, suggesting that additional factors, including diet and sexual attraction, may also be at play. Our species, Homo sapiens, first arose in Africa about 200,000 years ago, and researchers assume that its first members were as dark-skinned as Africans are today, because dark skin is advantageous in Africa. Dark skin stems from higher levels of the pigment melanin, which blocks UV light and protects against its dangers, such as DNA damage—which can lead to skin cancer—and the breakdown of vitamin B. On the other hand, skin cells need exposure to a certain amount of UV light in order to produce vitamin D. These competing pressures mean that as early humans moved away from the equator, it makes sense that their skin lightened. Recent research, however, has suggested that the picture is not so simple. For one thing, a number of genes control the synthesis of melanin (which itself comes in two different forms in humans), and each gene appears to have a different evolutionary history. Moreover, humans apparently did not begin to lighten up immediately after they migrated from Africa to Europe beginning about 40,000 years ago. In 2012, for example, a team led by Jorge Rocha, a geneticist at the University of Porto in Portugal, looked at variants of four pigmentation genes in modern Portuguese and African populations and calculated that at least three of them had only been strongly favored by evolution tens of thousands of years after humans left Africa. In January, another team, led by geneticist Carles Lalueza-Fox of the University of Barcelona in Spain, sequenced the genome of an 8000-year-old male hunter-gatherer skeleton from the site of La Braña-Arintero in Spain and found that he was dark rather than light-skinned—again suggesting that natural selection for light skin acted relatively late in prehistory. © 2014 American Association for the Advancement of Science

Keyword: Evolution; Aggression
Link ID: 19342 - Posted: 03.11.2014

Londa Schiebinger. In Madrid a couple of years ago, I was interviewed for Spanish newspapers. When I later ran the text through Google Translate, I got a shock: I was referred to repeatedly as “he”. Like much science and technology, Google Translate has a male default. When I drive a car, the seatbelt is not designed to accommodate breast tissue. Any medicines I take are more likely to have been tested on male than on female animals. There are moral issues here: women pay taxes and buy products and should not be short-changed. But scientific objectivity is at stake, too. Because medical research is done mainly in males, there is a male bias in, for example, the choice of drug targets. Science is halving the potential field of innovation. This is not about active discrimination; the bias is largely unconscious. Google Translate defaults to the masculine pronoun because 'he' is more commonly found on the Web than 'she'. Yet that is changing: an analysis of American-English texts in Google Books shows that the ratio of masculine to feminine pronouns has fallen to around 2:1, from a peak of 4:1 in the 1960s. In the summer of 2012, I invited Google and several language-processing experts to a Gendered Innovations workshop at Harvard University in Cambridge, Massachusetts. They listened to the problem for about 20 minutes, then said: “We can fix that!” Although it is complicated, the search for solutions is on. Fixing the problem is great, but constantly retrofitting for women is not the best road forwards. A better way is to include gender at all relevant phases of research — when setting priorities, gathering and analysing data, evaluating results, developing patents and, finally, transferring ideas to markets. Science and technology should take into account the biological and social needs of both women and men. Unconscious sex and gender bias can be socially harmful and expensive. © 2014 Nature Publishing Group

Keyword: Sexual Behavior
Link ID: 19329 - Posted: 03.06.2014

By Deborah Kotz Glaring gaps persist in medical researchers’ efforts to understand gender differences in common diseases, two decades after the passage of pivotal legislation mandating that more women be included in government-funded clinical trials, concludes a report being released Monday at a women’s health summit in Boston. The authors said research still lags on understanding how treatments for heart disease—the number one killer of women—affect the sexes differently, because women make up only one-third of the participants in clinical trials to test new drugs and medical devices, and most of these studies don’t report results for men and women separately. Women who don’t smoke are, for unknown reasons, three times more likely than non-smoking men to get lung cancer, but they’re still less likely than men to enroll in lung cancer studies, notes the report from Brigham and Women’s Hospital. And twice as many women suffer from depression as men, but fewer than 45 percent of animal studies to better understand anxiety and depression use female lab animals. “Women are now routinely included in clinical trials, but we are far from achieving equity in biomedical research,” said report leader Dr. Paula Johnson, executive director of the Brigham’s Connors Center for Women’s Health and Gender Biology. To address research disparities, the authors recommended that government agencies, drug manufacturers, hospital review boards that approve studies, and medical journal editors institute substantial changes to make women’s health a research priority. © 2014 Boston Globe Media Partners, LLC

Keyword: Sexual Behavior
Link ID: 19318 - Posted: 03.04.2014

by Clare Wilson More genetic mutations may be needed to give rise to autism in girls than in boys. The finding supports the notion that the female brain is somehow protected against autism, and this may in turn explain why four times as many males have autism than females. Although some cases of autism are associated with one mutation, most are thought to involve several genetic abnormalities. In the past few years, hundreds of mutations have been discovered that can make people more vulnerable to the condition. To see if the mutations affect men and women differently, Sébastien Jacquemont at the University Hospital of Lausanne in Switzerland and colleagues measured the frequency of two different kinds of mutation in 762 families that had a child with autism. Among the children with autism, one class of mutation known as a copy number variation – deletions or duplications of a large chunk of genetic material – was three times more common in girls than in boys. The team also found that substitutions of a single letter of DNA were about one-third more common in affected girls. Jacquemont says this suggests it takes more mutations for autism to arise in girls than in boys. "Females function a lot better than males with similar mutations," he says. The results reflect the "shielding" effect of being female, he says. "There's something that's protecting [their] brain development." A larger, as yet unpublished, study of about 2400 people with autism, conducted as part of the Autism Genome Project - an attempt to sequence the whole genome of 10,000 individuals affected by the condition – has produced similar results, says Joseph Buxbaum of Mount Sinai Hospital in New York. © Copyright Reed Business Information Ltd.

Keyword: Autism; Aggression
Link ID: 19311 - Posted: 03.01.2014

Sara Reardon A flipped mental switch is all it takes to make a fly fall in love — even if its object of desire is a ball of wax. A technique called thermogenetics allows researchers to control fly behaviour by activating specific neurons with heat. Combining the system with techniques that use light to trigger neurons could help to elucidate how different neural circuits work together to control complex behaviours such as courtship. Optogenetics — triggering neurons with light — has been successful in mice but has not been pursued much in flies, says Barry Dickson, a neuroscientist at the Howard Hughes Medical Institute's Janelia Farm Research Campus in Ashburn, Virginia. A fibre-optic cable embedded in a mouse’s brain can deliver light to cells genetically engineered to make light-activated proteins, but flies are too small for these fibre optics. Neither will these cells be activated when the flies are put into an illuminated box, because most wavelengths of visible light cannot penetrate a fly’s exoskeleton. Heat can penetrate the exoskeleton, however. Researchers have already studied fly behaviour by adding a heat-activated protein called TRPA1 to neural circuits that control behaviours such as mating and decision-making. When these flies are placed in a hot box, the TRPA1 neurons begin to fire within minutes and drive the fly’s actions1. But it would be better to trigger the behaviours more quickly. So Dickson’s lab has developed a system called the Fly Mind-Altering Device (FlyMAD), which uses a video camera to track the fly as it moves around in a box. The device then shines an infrared laser at the fly to deliver heat directly to the head. Dickson’s group presented the system last October at the Neurobiology of Drosophila conference at Cold Spring Harbor Laboratory in New York, and he is now submitting the work to a peer-reviewed journal. © 2014 Nature Publishing Group

Keyword: Sexual Behavior; Aggression
Link ID: 19310 - Posted: 03.01.2014

Carl Zimmer Forcing male flies into monogamy has a startling effect: After a few dozen generations, the flies become worse at learning. This discovery, published on Wednesday in the Proceedings of the Royal Society, isn’t a biological excuse for men who have strayed from their significant other. Instead, it’s a tantalizing clue about why intelligence evolved. The new study was carried out by Brian Hollis and Tadeusz J. Kawecki, biologists at the University of Lausanne in Switzerland. They investigated a fly species called Drosophila melanogaster that normally has a very un-monogamous way of life. To find a mate, the male flies seek out females on rotting pieces of fruit. They often engage in battles to chase their rivals away, and then pick a female to court. “The males will do this wing song, where they use one wing or the other to generate a song,” said Dr. Hollis. This wing song may last from 10 minutes to an hour. Virgin females usually accept the overtures. But if a female has just mated, she will reject a new male’s advances. “If a male comes at her from behind and she’s not interested, she’ll kick at him with her rear legs,” said Dr. Hollis. If a couple of days have passed since her last mating, however, the female may choose to mate again. Seven years ago, while he was a graduate student at Florida State University, Dr. Hollis set out to study how the competition among males shapes their evolution. He began breeding two groups of flies — one polygamous, the other monogamous. In 2011, he took his flies to the University of Lausanne, where he met Dr. Kawecki, an expert on learning. The two scientists wondered if the different mating habits of Dr. Hollis’s flies had altered their brains. © 2014 The New York Times Company

Keyword: Sexual Behavior; Aggression
Link ID: 19309 - Posted: 03.01.2014

Brian Owens The distinctive aroma of goats does more than just make barnyards extra fragrant. Male goats can use their heady scent to make female goats ovulate simply by being near them. Researchers had ascribed this 'male effect' to chemicals known as primer pheromones — a chemical signal that can cause long-lasting physiological responses in the recipient. Examples of primer pheromones are rare in mammals; the male effect in goats and sheep, and a similar effect in mice and rats, where the presence of males can speed up puberty in females, are the only known cases. But exactly what substances are at work and how has remained a mystery. Now, reproductive biologist Yukari Takeuchi from the University of Tokyo and her colleagues have identified a single molecule, known as 4-ethyloctanal, in the cocktail of male goat pheromones that activates the neural pathway that regulates reproduction in females1. ”It has long been thought that pheromones have pivotal roles in reproductive success in mammals, but the mechanisms are scarcely known,” says Takeuchi. The researchers found that male goat pheromones are generally synthesized in the animal's head skin, so they designed a hat containing a material that captured their odorous molecules and placed them on the goats for a week to collect the scent. Analysis of the gases collected identified a range of compounds, many of which were unknown and were not present in castrated males. When exposed to a cocktail of 18 of these chemicals, the brains of female goats showed a sudden increase in the activity of the gonadotropin-releasing hormone (GnRH) pulse generator — the neural regulator of reproduction. © 2014 Nature Publishing Group,

Keyword: Chemical Senses (Smell & Taste); Aggression
Link ID: 19308 - Posted: 03.01.2014