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

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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

On 24 February, Uganda’s president, Yoweri Museveni, signed a draconian Anti-Homosexuality Bill into law, after 2 months of declining to do so. Science, he says, changed his mind—in particular, the findings of a special scientific committee his Health Ministry had appointed earlier in the month. “Their unanimous conclusion was that homosexuality, contrary to my earlier thinking, was behavioural and not genetic,” Museveni wrote to President Barack Obama on 18 February, in response to Obama’s pleas that he not sign the bill. “It was learnt and could be unlearnt.” But some scientists on the committee are crying foul, saying that Museveni and his ruling party—Uganda’s National Resistance Movement (NRM)—misrepresented their findings. “They misquoted our report,” says Paul Bangirana, a clinical psychologist at Makerere University in Kampala. “The report does not state anywhere that homosexuality is not genetic, and we did not say that it could be unlearnt.” Two other committee members have now resigned to protest the use of their report to justify the harsh legislation, which mandates life imprisonment for “aggravated homosexuality,” such as sexual acts with a minor, and prison terms of 7 to 14 years for attempted and actual homosexual acts, respectively. The law was first introduced into Uganda’s Parliament in 2009, but withdrawn after widespread objections to provisions that could have included the death penalty. As he signed the new version, passed by Parliament last 20 December, Museveni claimed that “mercenaries” were recruiting young people into gay activities. © 2014 American Association for the Advancement of Science

Keyword: Sexual Behavior; Aggression
Link ID: 19296 - Posted: 02.26.2014

By Sandhya Somashekhar, The Food and Drug Administration has approved 24 drugs for the treatment of male sexual dysfunction. For women, that number is zero. The disparity reflects drugmakers’ difficulties in unlocking the secret to revving up women’s sex drive. It also has become a rallying point for women’s advocates and even some members of Congress, who suggest that federal regulators seem more eager to approve sex-enhancing drugs for men than for women. It isn’t every day that political leaders and groups such as the National Organization for Women get involved in the drug- approval process, particularly for “lifestyle” drugs. But the unsuccessful quest for a “female Viagra” is sparking complicated questions about a woman’s right to a pill that may improve her sex life — and about how much of a libido lift is enough to be judged effective by the FDA. A drug called flibanserin, touted by some as the “little pink pill,” the counterpoint to Viagra’s little blue pill, was developed 12 years ago. Last month, women’s groups were disappointed when the FDA asked for further safety tests on the medication. 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. “It looks to me like there are more hurdles being put in front of this drug than there have been on drugs addressing male dysfunction,” said Terry O’Neill, president of NOW. “Obviously, everyone only wants drugs to get on the market if they are proven safe and effective. But we don’t want attitudes to get in the way of a good drug.” © 1996-2014 The Washington Post

Keyword: Sexual Behavior
Link ID: 19274 - Posted: 02.20.2014

By PAUL VITELLO Alison Jolly, an American-born primatologist whose research in the forests of Madagascar shed new light on the evolution of social intelligence and helped disprove a longstanding scientific tenet that males were dominant in every primate species, died on Feb. 6 in Lewes, East Sussex, England. She was 76. The cause was breast cancer, said Barbara Orlando, a longtime friend. Dr. Jolly’s two major insights emerged from her 1960s field studies of the lemur, a primate whose development in relative isolation on the island of Madagascar makes the species something akin to a living fossil. Dr. Jolly cited lemurs’ complex social relationships as evidence of an unexplored trail in one of anthropology’s great mysteries: the evolution of higher intelligence. Writing in the journal Science in 1966, she suggested that the many hours lemurs spent in play, mutual grooming and social networking — activities that establish the social ties and hierarchies that determine access to food, mate selection and migration patterns — may have been as important to the evolution of intelligence as the development of weapons and tools of hunting and protection, then considered the hallmarks of evolutionary advance. More unnerving to colleagues was her discovery that in some primate species, females run the show. The finding upended a bedrock assertion in evolutionary biology — based on studies of chimpanzees and orangutans in captivity — that males dominated females in every primate species, including humans. “Females have social, spatial and feeding priority over males,” Dr. Jolly wrote in describing the feeding, mating, child-rearing and recreational habits of the ring-tailed lemur, one of about 100 recognized species of lemur, of which more than a dozen are female-dominant. Among the ring-tailed lemurs, Dr. Jolly wrote in “Lemur Behavior: A Madagascar Field Study,” “all females, whether dominant or subordinate in the female hierarchy, are dominant over males.” © 2014 The New York Times Company

Keyword: Evolution; Aggression
Link ID: 19265 - Posted: 02.19.2014

Ian Sample, science correspondent, in Chicago Researchers have found evidence – if evidence were needed – that men have less sex after becoming a father for the first time. A study of more than 400 young men in the Philippines found that their sex lives declined significantly when they had their first child. The fall in sexual activity was associated with the men's testosterone levels, which are known to fall when men start families, but the latest research shows that the greater the fall in testosterone, the less sex men reported. Lee Gettler, an anthropologist at the University of Notre Dame in Indiana, gathered medical and lifestyle information on the men from the ages of 21 to 26 years old and found there were physiological and behavioural changes as some of them married and had children. When men got married their testosterone levels fell, and declined even further when they had their first child. That led to the question of whether falling testosterone might impact on their sex lives. "I didn't think that testosterone would be linked to men's sexual behaviour, but when we tested it we found that as men transitioned to fatherhood, the more their testosterone declined the less frequently they reported having sex with their partner," Gettler said. "Does this mean that men who care for children have low testosterone and no sex? No, it has nothing to do with childcare." The impact on men's sex lives was not linked to the amount of time and energy they invested in childcare, he said. Gettler described his research at the annual meeting of the American Association for the Advancement of Science in Chicago. © 2014 Guardian News and Media Limited

Keyword: Hormones & Behavior; Aggression
Link ID: 19250 - Posted: 02.15.2014

By SINDYA N. BHANOO Mosquito sperm have a sense of smell, researchers are reporting, in a finding that could suggest ways to help control the spread of disease-carrying insects. The sperm carries a set of chemical sensors identical to the olfactory receptors on the mosquitoes’ antennas, according to a study in Proceedings of the National Academy of Sciences. Mosquitoes mate just once in their lifetime, and the female stores the male’s sperm in an organ called a spermatheca. Before the eggs mature, the female seeks out blood using the receptors on her antennas. Soon after, chemical signals cause the sperm tails to beat rapidly and start the fertilization process. “The sperm may need a chemical signal to become ready for fertilization,” said Jason Pitts, a researcher at Vanderbilt University and an author of the study, which was supported by the Gates Foundation as part of its efforts to improve global health. Another author, Laurence Zwiebel, also a Vanderbilt researcher, called the dual use of the olfactory receptors a clear and clever example of convergent evolution: The mosquitoes, he said, “found something that works and use it in multiple ways.” The scientists think olfactory receptors may exist on the sperm of many other insects, and they are developing chemical compounds that can be applied to breeding grounds to block the receptors. “You can effectively confuse the sperm or make them inactive,” Dr. Zwiebel said. © 2014 The New York Times Company

Keyword: Chemical Senses (Smell & Taste); Aggression
Link ID: 19241 - Posted: 02.12.2014

By JOHN LA PUMA SANTA BARBARA, Calif. — A FUNNY thing has happened in the United States over the last few decades. Men’s average testosterone levels have been dropping by at least 1 percent a year, according to a 2006 study in The Journal of Clinical Endocrinology and Metabolism. Testosterone appears to decline naturally with aging, but internal belly fat depresses the hormone further, especially in obese men. Drugs like steroids and opiates also lower testosterone, and it’s suspected that chemicals like bisphenol A (or BPA, commonly found in plastic food containers) and diseases like Type 2 diabetes play a role as well. Men feel the loss. Clinical testosterone deficiency, which is variously defined as lower than 220 to 350 nanograms of testosterone per deciliter of blood serum, can cause men to lose sex drive and fertility. Their bone density often declines, and they may feel tired and experience hot flashes and sweats. But “low T,” as the condition has been labeled, isn’t nearly as common as the drug ads for prescription testosterone would have you believe. Pharmaceutical companies have seized on the decline in testosterone levels as pathological and applicable to every man. They aim to convince men that common effects of aging like slowing down a bit and feeling less sexual actually constitute a new disease, and that they need a prescription to cure it. This is a seductive message for many men, who just want to feel better than they do, and want to give it a shot, literally. The problem is that prescription testosterone doesn’t just give your T level a boost: it may also increase your risk of heart attack. It can add huge numbers of red blood cells to your bloodstream and shrink your testes. In some men, it increases aggression and irritability. © 2014 The New York Times Company

Keyword: Hormones & Behavior
Link ID: 19238 - Posted: 02.11.2014

by Laura Sanders A new analysis of cows shows that mamas make more milk for daughters. Other studies have hinted that human moms produce different milk for sons than for daughters, so perhaps lactating women also boost production for daughters. I love eavesdropping on people’s overly detailed coffee orders. You, sir, with the temerity to order a skinny split quad shot latte no whip no foam, with a side of lemon? Your extreme customizing just made my day. Such personalization was running through my mind as I read a recent study on cows. It turns out that another beverage is also subject to the specific, exacting standards of its drinker: milk. And the customer’s bossy demands seem to start before he or she is born. Heifers produce more milk for daughters than sons, Katie Hinde and colleagues report February 3 in PLOS ONE. When a cow gives birth to her first female, she makes about 1.6 percent more milk than she would have for a son, Hinde and colleagues found by analyzing the dairy records from a million and a half cows. And because calves born at dairy farms are taken away from their mothers soon after birth, the female calves’ requests to “make me more milk” must have come during pregnancy. Another interesting finding: The first pregnancy had an outsized effect on the cow’s future milk production. Cows that had sons first saw a slight bump in production when they got pregnant with a daughter, but didn’t catch up to the cows that had a daughter followed by a son. The first born daughter set the mom’s milk-making machinery on high, and that’s where it stayed for subsequent pregnancies. © Society for Science & the Public 2000 - 2013

Keyword: Sexual Behavior
Link ID: 19237 - Posted: 02.11.2014

You probably saw dozens of people’s faces today, many more if you live in a city. You may not have been conscious of it, but you were subtly judging every one by its beauty. Your eyes are drawn to more attractive faces, and the almost inescapable result is that more attractive people have advantages in almost every aspect of life, from job interviews to prison sentencing. But what drives us to crave beauty? According to one theory, gazing upon beauty stimulates the brain’s μ-opioid receptors (MOR), thought to be a key part of our biochemical reward system. At least in rodents, stimulating or inhibiting MOR neurotransmission not only tweaks the animals’ appetite for sex or food, but also the strength of their preferences for particular foods or mates. Is our preference for pretty faces driven by the same biochemical reward circuit? To find out, researchers invited 30 heterosexual men to browse a series of female faces on a computer (one pictured). Each man received either a dose of the MOR-stimulating drug morphine, the opioid receptor–inhibiting drug naltrexone, or a placebo. The results, published today in Molecular Psychiatry, suggest that we seek out beautiful faces at least in part because our brains reward us. Not only did stimulating MOR neurotransmission cause men to linger longer on faces that they rated as more beautiful, but the beauty rating also became more extreme, with beautiful faces rated as even more attractive relative to the rest of the faces. Inhibiting MOR had the opposite effects. The findings are yet more evidence that our social interactions are strongly influenced by the invisible hand of evolution, pushing us to find attractive mates. But the question remains, how do we decide which face is attractive in the first place? © 2014 American Association for the Advancement of Science

Keyword: Sexual Behavior; Aggression
Link ID: 19232 - Posted: 02.11.2014

Women have a poorer quality of life after a stroke than men, a study has found. The US research, published in Neurology, assessed the mental and physical health of 1,370 patients three months and a year after a stroke. Women had more depression and anxiety, pain and discomfort, and more restricted mobility. UK experts said women tended to have strokes later, and might therefore need more support. But the study did say more people survive a stroke now than 10 years ago because of improved treatment and prevention. The researchers at Wake Forest Baptist Medical Center, North Carolina, looked at patients who had had a stroke or transient ischaemic attack (TIA), also known as a mini-stroke. Quality of life is calculated using a formula that assesses mobility, self-care, everyday activities, depression/anxiety and pain. At three months, women were more likely than men to report problems with mobility, pain and discomfort, anxiety and depression, but the difference was greatest in those aged over 75. After a year, women still had lower quality-of-life scores overall than men but the difference between them was smaller. Support needs Prof Cheryl Bushnell, who led the study, said: "We found that women had a worse quality of life than men up to 12 months following a stroke." BBC © 2014

Keyword: Stroke; Aggression
Link ID: 19221 - Posted: 02.08.2014

By Matt McGrath Environment correspondent, BBC News Successful professional cyclists are seen as more handsome than their struggling colleagues, according to new research. Women rated facial attractiveness among riders in the 2012 Tour de France, won by Britain's Sir Bradley Wiggins. The top 10% of performers were rated on average as 25% better looking than the laggards. The scientists conclude that humans have evolved to recognise athletic performance in faces. The research has been published in the Royal Society journal, Biology Letters. Some biologists argue that evolution has shaped women to select mates on the basis that they would either make good fathers or would pass on good genes. Healthy, physically fit men would on average be seen as more attractive by women. A number of other studies in recent years have suggested that women have a sophisticated radar for athletic performance, rating those with greater sporting skill as more attractive. This new work, though, set out to test if the same applied to more inherent physical qualities such as stamina and endurance. Cycle of life Dr Erik Postma, from the Institute of Evolutionary Biology at the University of Zurich, asked people to rate the attractiveness of 80 professional cyclists from the 2012 Tour de France. The cyclists were all of a similar physical stature, were tanned and around the same age. BBC © 2014

Keyword: Sexual Behavior; Aggression
Link ID: 19214 - Posted: 02.06.2014